GSCE Biology Flashcards

Question

presence of secondary consumers (predators) caused primary consumers (prey) to evolve much more quickly

Answer 1

prey eaten by predator | ones better adapted/suited, more likely to survive, reproduce and pass on alleles

Answer 2

occuring outside of cell | occuring inside cell

Answer 3

movement from low to high concentration, against concentration gradient using energy ATP to be able to do it- got from respiration

Answer 4

low rate of aerobic respiration | low rate of growth/reproduction

Answer 5

to release energy to take in minerals/nutrients by active transport

Answer 6

cells full of water | cells turgid

Answer 7

yes x rays easy to do/routine/info helps doctor | no x rays/costly/harmful to the babies as it exposes them to radiation early/rare condition only 6300 have it

Answer 8

heart and blood vessels

Answer 9

transports substances | plays role in immune system

Answer 10

plasma 55% red blood cells 44% white blood cells- small part platelets

Answer 11

90% is water alot of materials are transported in plasma by being dissolved in the plasma (includes nutrients, waste products, hormones, antibodies) blood cells are suspended in the plasma.

Answer 12

red- contains haemoglobin pigments haemogloblin (protein) binds to oxygen to form oxyheamoglobin and allows the red blood cells to transport oxygen from the lungs to all parts of the body

Answer 13

help defend the body from infectious disease-causing microbes (pathogens( some non speicfic, some specific. some white bleed cells engulf and digest pathogens- releases enzymes when pathogen engulfed, lysozymes that break down pathogens lymphocytes produce antibodies

Answer 14

high SA:V due to biconcave shape | no nucleus so can have lots of haemoglobin

Answer 15

small fragments of cells which are involved in making clots stops bleeding prevent entry of pathogens

Answer 16

arteries veins capillaries

Answer 17

``` carry blood away from heart high pressure blood no valves thick wall to withstand high pressures small lumen ```

Answer 18

carry blood into the heart | low pressure of blood

Answer 19

carry blood to the cells allows diffusion of molecules between blood and cells low pressure of blood no valves thin wall- only one cell thick (to allow diffusion) very small lumen

Answer 20

ribosomes in cytoplasm haemoglobin is protein gene is transcribed to mRNA mRNA is sent to cytoplasm - goes to ribosomes ribosome makes protein - translate mRNA to protein

Answer 21

haemoglobin binds to oxygen = oxyhaemoglobin that is sent to body cells oxyhaemoglob breaks up= haemoglobin + oxygen oxygen diffuses into cells

Answer 22

contains adult stem cells that are undifferentiated (not specific) if red cells needed, specialized is stem cells to red cells

Answer 23

``` Relatively cheap Can be used in the field Does not require specialist training Can look at living specimens —————————————————— Low resolution (200nm) as limited by the wavelength of visible light Low magnification strength (x1500) Staining is required for some organelles to present ```

Answer 24

Magnification = degree to which the size of an image is larger than the real object Magnification of an object= image size/object size Magnification of microscope = magnification of eyepiece lens x magnification of the objective lens —————————————————— Resolution = ability to distinguish between 2 points that are close to each other as separate objects

Answer 25

- stain drop, if specimen transparent/colourless (easier to see) - place cover slip at a angle with mounted needle and lower it on top (protect lens) - gently press, remove any air bubbles - slide mounted onto stage - lamp at bottom shines light on slide so specimen can be viewed, line specimen at the centre of stage so light passes through - use coarse adjusting knob to move stage just below the lowest power objective lenses and then bring it into focus by moving it further away. - adjust focus w/ fine focus adjustment knob until there's clear image of specimen - objective lens magnifies the image which is further magnified by eyepiece lens

Answer 26

Prokaryotic cells: 0.2-2um Cell membrane , Cytoplasm, Cell wall, Single loop of DNA, Plasmid Flagellum (sometimes) ————————————————- Eukaryotic cells: 5-100um (Animal) Nucleus , Cytoplasm, Mitochondria, Ribosomes, Cell membrane (Plant) Nucleus, Cytoplasm, Mitochondria, Ribosomes, Cell membrane, Cell wall, Vacuole, Chloroplast

Answer 27

Nucleus: contains genetic material (DNA in the form of chromosomes) and controls cell’s activities like cell division Cytoplasm: gel-jelly like substance where most of the chemical reactions happen, contains dissolved nutrients and salts and organelles and enzymes Mitochondria: contains enzymes for aerobic respiration+ energy released, provides energy for cells from aerobic respiration Ribosomes: protein synthesis. Found on a structure (rough endoplasmic reticulum) Cell membrane: has a selective barrier, semipermeable, receptors which identifies and selectively controls the movement of substances in and out of a cell, holds the cell together. Cell wall(plant)- made up of cellulose fibres, strengthens cell and supports plant, maintains cell shape. The pressure created by the cell wall stops too much water entering and prevents cell lysis Cell wall(bacterium)- made of peptidogylcan/murein, strengthens cell, maintains cell shape Vacuole: filled with cell sap to help keep the cell turgid Chloroplast: contains green pigment chlorophyll which absorbs light energy for photosynthesis, contains the enzymes needed for photosynthesis, provides glucose Single loop of DNA: single molecule found free in the cytoplasm Plasmid: circular pieces of dna found in bacteria, can act as a vector to transfer dna from one organism to another. Flagella: can rotate or move in whip like motion to move bacterium

Answer 28

magnification + resolution of light microscope is too low Electron microscope - electrons to form image. Electrons have a smaller wavelength than of light waves and so allows scientists to view smaller sun cellular structures revealed structures not visible with the light microscope and in more detail (e.g mitochondria that’s needed for aerobic respiration,chloroplasts that’s needed for photosynthesis) Has helped scientists to figure out how they function in a cell.

Answer 29

SEM= Scanning Electron Microscope - creates 3D images at a lower resolution. Large depth field. Surface structure of specimen - 10nm~ 50nm resolution, x100,000~x30,000 magnification ———————————————— TEM = Transmission Electron Microscope - creates 2D images detailing organelles at much higher resolution Examine thin slices/sections of cells/tissues - 0.2nm resolution - x500,000~ x1,000,000 magnification Advantages- Can see very small organelles Can produce 3D images (SEM) Disadvantages- - Samples need to be placed in a special vacuum so cannot look at living specimens - extremely expensive - very large so cannot be moved easily - requires specialist training and skill

Answer 30

Dna is a polymer made out of monomers nucleotides. It’s two strands of complementary base paired nucleotides twisting around each other, forming a double helix held together by weak hydrogen bonds between A-T and G-C pairs. Phosphate backbone and deoxyribose sugar attached to a base

Answer 31

Thymine Adenine Guanine Cytosine

Answer 32

Transcription : DNA in nucleus and cannot leave. Dna unzips. Complementary to DNA’s template strand, mRNA is formed. mRNA leaves nucleus to ribosomes in cytoplasm Translation: tRNA has anticodons complementary to mRNA’s codons. tRNA carries a amino acid. mRNA’s sequence of bases corresponds to the order of amino acids. tRNa attaches to mRNA. Forms a amino acid chain. Chain folds and forms a unique 3D structure protein

Answer 33

Each amino acid is coded by a codon (3 bases). mRNA’s sequence of bases corresponds to the specific order of amino acids. tRNA ( which carries the amino acid) attaches to the mRNA in a specific order, as its anticodons are complementary to the mRNA. Different sequence of amino acids produces different proteins. mRNA is made from copying the base sequence of DNA therefore proteins depend on the DNA.

Answer 34

Catalase breaks down hydrogen peroxide. Cut potato cylinders using cork borer n drop into conical flask w/ hydrogen peroxide. Record volume of oxygen released using gas syringe. rate of reaction= volume of oxygen/time taken. Repeat w/ different concentrations of hydrogen peroxide. Solution of sodium carbonate and milk (alkaline cuz of the sdc) Phenolphalein indcitator added. pink. Add lipase, it breaks down the lipids in the milk producing fatty acids which lowers the pH of solution into acidic, colourless. Use 1 divided by time. Different temperatures affect rate of reaction - Amylase breaks down starch. Test tubes containing different pHs. Place mixture of amylase and starch in. Remove a sample, test for presence of starch w iodine solution- blue/black colour when starch is present. When all starch is broken - amylase, iodine will not turn and remain orange-brown as starch is not present anymore, record time for the disappearance of starch. Use 1 divided by the time.

Answer 35

Iodine test for starch - grind sample. add iodine solution to sample, turns blue/black in presence of starch Benedict’s test for reducing sugars: add benedicts solution turns blue to orange/brick red when heated with a reducing sugar. *sucrose is a non-reducing sugar and does not react with Benedict’s solution* Emulsion test for lipids: add ethanol and then water. Cloudy white emulsion forms between lipid and water or rub brown paper on lipid, paper goes see-through Biuret test for proteins- Add Biuret reactant to solution. Turns mauve/purple

Answer 36

Enzymes have an specific-shaped active site Where specific substrates collide with and bind Forming a enzyme-substrate complex Lock and key theory Extreme heat or pH can denature enzymes by changing the shape of the site and preventing substrate binding Chemical reaction takes place and Enzyme-product complex is formed and products are released

Answer 37

Cellular respiration: Universal chemical process Occurs continuously To supply ATP in living cells transferring energy from breakdown of glucose Controlled by enzymes Rate affected by temperature and pH Exothermic respiration - heat energy released from glucose. More bonds made than broken.

Answer 38

Aerobic: Plentiful oxygen available, mitochondria Most efficient way to transfer energy from glucose. Oxidation of glucose complete. Produces lots of ATP-32 molecules per molecules of glucose Respiration used the most Glucose + oxygen -> carbon dioxide + water Anaerobic: short/no oxygen supply cytoplasm Less efficient way to transfer energy from glucose. Oxidation of glucose is incomplete and products of respiration still contain energy. 2 molecules of ATP per molecule of glucose, less energy released than aerobic but quick. Anaerobic respiration in animals: glucose -> lactic acid Anaerobic respiration in plants: glucose-> ethanol + carbon dioxide In conditions like waterlogged soil, plants respire anaerobically fungi respire anaerobically too yeast (fungi) anaerobic respiration=fermentation

Answer 39

Extra: oxygen debt Vigorous exercise= body can’t supply enough oxygen to your muscles for aerobic Muscles start respiring anaerobically, heart rate + breathing rate increases Glucose is only partially broken down and lactic acid is produced Lactic acid builds up in muscles(oxygen debt)= pain + muscle fatigue Extra oxygen needed to break down the lactic acid that’s built up In order for aerobic respiration to take place That why we breath heavy after vigorous exercise

Answer 40

Synthesis: Monomers are simple sugars Monomers are joined to make polymers in long chains- large complex carbohydrates e.g starch Breakdown: Complex carbohydrates too large to be absorbed by walls of digestive system Polymer molecules can be broken down into simple sugar monomers which can be absorbed into the blood stream chemical bonds between monomers are broken by enzymes amylase in the mouth and intestine

Answer 41

Proteins are polymers made up of long chains of amino acids monomers Too large to pass through gut wall broken down by enzymes protease in stomach and small intenstine back into monomers Then amino acids are used for protein synthesis They form a large chain and fold to make a protein structure

Answer 42

Lipids = glycerol and 3 fatty acids They are not polymers because they don’t form a large chain of repeating units lipids broken down by enzymes lipase in the small intestine

Answer 43

They convert energy from the sun into glucose during photosynthesis producing biomass, this feeds the rest of the food chain

Answer 44

Chlorophyll absorbs light energy. CO2 enters plant by diffusion. Water enters plant through osmosis in the roots. Light energy is used to split water, releasing oxygen gas and hydrogen ions Enzymes combine carbon dioxide gas with the hydrogen to make glucose Location of photosynthesis: chloroplasts As it contains chlorophyll which absorbs the light energy

Answer 45

Photosynthesis is an endothermic reaction as it requires light energy for the reaction to split up water into hydrogen and oxygen, the light energy is absorbed by chlorophyll It takes in (light) energy

Answer 46

Effect of light intensity on photosynthesis in water plants: - capillary tube is attached to syringe + contains water that leads into test tube - lamp , changing distance - oxygen bubbles produced as it photosynthesis, forms gas tube in capillary tube. Use gas syringe to measure/oxygen concentration in water w data logger+ oxygen sensor - more bubbles produced w closer distance as + photosynthesis at higher light intensities Effect of different wavelengths of light on photosynthesis - different wavelengths, coloured acetate filters - effects of blue, green and red of the spectrum on photosynthesis - chlorophyll absorbs light energy - reflects green light, absorbs blue and red light. (Before using iodine, place lead in boiling water (kill n preserve) then again w boiling tube n ethanol (removes chlorophyll) Effect of chlorophyll on photosynthesis - presence or absence of chlorophyll effects - variegated plant(white and green) - test for photosynthesis (glucose produced->starch) using iodine solution, will turn black/green on the areas of the leaf with chlorophyll Effect of light exclusion on photosynthesis - cover part of the leaf and leave it for some time - cover it with iodine solution - areas exposed to light stain blue-black and the area that had light blocked remains orange-brown colour - as iodine turns blue/black in presence of starch

Answer 47

Temperature- optimum 37 oC Reaction rate increases w increase temp too high- bonds in enzyme structure break>change shape(denatures)>substrate no longer fits pH- too high/low, forces that hold the amino acid chains will be affected> denatures> substrate no longer fits Substrate concentration- Higher conc= higher rate initially Enzymes more likely to collide w substrate. After a while, no effect as active sites are all full Enzyme concentration Initial increase, stops increasing. Limiting factor is substrate.

Answer 48

plant needs light energy to break water into hydrogen and oxygen - increase CO2 is one of the reactants - increase Chemical reactions that combine CO2 and H2O are controlled by enzymes - increase, too high temp: decrease

Answer 49

If light intensity increases, rate increases but then will stop increasing as it’s not light intensity that is the limiting factor anymore, this applies to all of the factors

Answer 50

Diffusion- Gas and liquids. down concentration gradient. no energy required. (Particles move in both directions but net movement from high to low). Passive Examples- Liver: Diffusion of urea from liver cell (high urea concentration) to blood vessel (low concentration) Lungs: Diffusion of CO into alveoli (low concentration) from blood (high concentration ), diffusion of oxygen out of alveoli (high) into blood (low) Leaf: O2 diffuses out of cells (high concentration), CO2 diffuses into cell (as it has low concentration)

Answer 51

Movement from high to low water potential. Down concentration gradient. partially permeable membrane. Water molecules only. No energy required. Passive. WHEN concentration same on both sides, movement of water is same in both directions (no net movement) ``` Examples: Root hair cells take up water water moves into plant cell, turgid, water moves out of plant cell, plasmolysed/flaccid. Water moves into animal cell, bursts Water moves out of animal cell, shrivel ```

Answer 52

Particles go against concentration gradient. Low to high. Requires energy (ATP) Examples: Mineral ions from soil move to roots via active transport Glucose from small intestines move to blood via active transport

Answer 53

Interphase- Cellular growth (organelles double). DNA replicates and forms two copies of each chromosome, -dna unzips -forms two seperate strands -bases on each strand exposed -free nucleotides line up against each of the strands (complementary pairing) -forms DNA base pairs -when strand complete, forms two identical molecules of dna Mitosis- (Prophase- nuclear envelope breaks down.Metaphase= chromosomes line up along equator.Anaphase- chromosomes move to opposite ends of the cells.Telephrase- new nuclear envelope reforms around each set of chromosomes - two nuclei ) Cytokinesis- cell membrane pinches inward, separates and enclose the two nuclei and split cell into two new identical daughter cells. Cytoplasm and cell membrane divided. - cell stops dividing temporarily -cycle repeats

Answer 54

So the cells can develop sub cellular structures that enable them to fulfil specific functions and to be suited to its role in the body to be efficient

Answer 55

Growth and development Replacing old/damaged cells. Asexual reproduction

Answer 56

embryos and adult animals and meristems in plants

Answer 57

Undifferentiated. can continuously undergo cell division. Provides new cells for growth, and to replace damage/dead specialised cells (specialised cells often lose ability to make new copies of themselves)

Answer 58

Embryonic- Only in embryos. Can differentiate into any cell type. Totipotent. Adult stem cells- Developed adult organisms. Specific areas of the body( bone, marrow, brain, muscle, skin and heart for a human). Differentiate into a narrower range of cell types (limited). Pluripotent

Answer 59

organism size increases=surface area:volume decreases. Less surface area for substances to diffuse through + distance from body cells to outer environment is larger + need more energy = diffusion rate too slow to meet cell requirements e.g supplying necessary molecules. Exchange surfaces: increase surface area to volume ratio for faster diffusion Transport system: Efficient, carry substances to/from cells required for survival and to remove waste.

Answer 60

Oxygen- release energy from food molecules Carbon dioxide(respiration)- photosynthesis, glucose. Affects blood pH, acidic, regulate. Water- metabolic processes and transport of soluble substances, regulates body temperature. photosynthesis in plants Dissolved food molecules- necessary nutrients, supplies energy and raw materials Mineral ions- lack of minerals=deficiencies. Example: calcium - healthy bones, iron- haemogloblin. In plants: Magnesium - chlorophyll, nitrates - proteins Urea- metabolism of proteins in liver, ammonia is formed. Liver converts toxic ammonia to non toxic compound urea + extra nitrogen is expelled from body through urea These substances exchange through the cell membrane through diffusion, osmosis and active transport

Answer 61

``` Double circulatory. blood passes throu heart 2x. 2 circuits: Pulmonary circuit( heart - lungs) deoxy. Systemic circuit (heart -other organs) Capillaries connect arteries and veins allow substances to be diffused into body tissues. After deoxygenated blood passes through the capillaries it enters the smallest veins called venules, from the venules it flow into progressively larger and larger veins until it reaches the heart. Oxygenated blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until it results in arterioles (microscopic arteries). ```

Answer 62

Swapping of gases that occur at the exchange surfaces Allows oxygen to travel into cells for respiration whilst removing CO2 Transferring CO2 from blood into lungs then the air Transferring oxygen from air into lungs into blood Air enters the body through the mouse or nose and quickly moves to the pharynx. From there it passes through the larynx and enters the trachea Within the lungs, the trachea branches into a left and right bronchus which divides into smaller branches called bronchioles. The smallest bronchioles end in tiny air sacs called alveoli During gas exchange, oxygen moves from the lungs to the bloodstream At the same time, carbon dioxide passes from blood to the lungs It happens between the alveoli and capillaries located on the walls of alveoli The capillaries let oxygen and tissue diffuse between the respiratory system and bloodstream Oxygen molecules attach to the red blood cells which travel back to the heart And carbon dioxide molecules in the alveoli are taken out of the body when a person exhales

Answer 63

``` Arteries The largest artery is the aoarta Carries blood away from heart, Thick, elastic, muscular wall to withstand blood flowing at high pressure as it leaves the heart Small lumen ``` Veins- Carry blood towards the heart Thinner walls Large lumen Contains valves to prevent back flow of blood Carries blood at lower pressure so does not need thick walls Capillaries: Site of gas exchange between the blood and the tissues. Allows diffusion of gases and nutrients from blood into the body cells Very thin, one cell thick wall Very small, only allows blood to pass through one cell at a time. Walls are made of a semi permeable membrane to allow transport of gases and nutrients into and out of the blood

Answer 64

Deoxygenated blood from the body enters the right atrium from vena cavas Blood passes through right atrium to the right ventricle then to lungs through pulmonary arteries Oxygenated blood from lungs enters the left atrium through pulmonary veins The left ventricle of the heart is larger and thicker than the right ventricle as it has to pump blood further around the body and against higher ventricle The walls of the ventricles are much thicker than those of the atria as they are responsible for pumping blood out of the heart so need to generate a higher pressure Superior vena cava carries blood from head, neck, arms, and chest Inferior vena cava carries blood from legs, feet and organisms in the abdomen and pelvis The vena cava is the largest vein in the body Carries deoxygenated blood from body to heart

Answer 65

Vena cavas > right atrium > right ventricle > pulmonary arteries > lungs > pulmonary veins > left atrium > left ventricle > aorta > body

Answer 66

Values: open and close, allowing blood to flow to the correct places and prevent blood flowing backward This tricuspid valve: from right atrium to right ventricle Mitral value (also known as biscupid value): help blood pass from left atrium to left ventricle Aortic value: from left ventricle to aorta Pulmonary value: the right ventricle to pulmonary artery

Answer 67

Red blood cells: transport oxygen required for aerobic respiration in body cells Adapted: - contains protein haemoglobin that can combine with oxygen or release (oxyhaemoglobin to haemoglobin + oxygen, or haemoglobin + oxygen to oxyhaemoglobin) - No nucleus - do can pack in more haemoglobin - Small and flexible so can fit through narrow blood capillaries - biconcave shape to maximise surface area for oxygen absorption - thin so only a short distance for oxygen to diffuse to reach centre of cell

Answer 68

Plasma: transporting carbon dioxide, digested food molecules, urea and hormones, distributing heat Adapted: made primarily of water. Many of the molecules the body needs to transport (e,g urea, carbon dioxide and glucose are soluble in water so a large number of substances can be transported around the body in plasma

Answer 69

ingesting pathogens (phagocytes do that) and producing antibodies (lymphocytes do that) Adapted: Phagocytes: Irregular shape, they can change shape to squeeze out of blood vessels and get to the site of infection. Others have cytoplasm which can flow making it possible for cell to change shape to surround and engulf bacteria. Have enzymes inside cell that breaks down pathogen in order to destroy it Lymphocytes: Produces soluble proteins called antibodies when a foreign body enters the body

Answer 70

Platelets: blood clotting, stopping bleeding. Cell fragments, giant cells, bone marrow. Adapted: proteins on surface, enable stick to breaks in blood vessel, clog bleeding + can clump together secrete proteins - results in series of chemical reactions that form blood clot - plugs a wound- blood clot dries to scab

Answer 71

Water - osmosis Mineral ions - active transport Root hair structure: -large surface area to increase rate of absorption -lots of mitochondria,releases energy from glucose during respiration, provides energy needed for active transport

Answer 72

Transpiration: opens stomata for CO2, spongy+palisade mesophyll cells evaporate. Because strong cohesion between water molecules cuz of hydrogen bonding so water pulled up (pull) in the transpiration as water evaporates(stream) ———————————————- Translocation process Glucose -> sucrose, transported around plant in phloem vessels. sucrose -> glucose for respiration Movement of dissolved substances (e.g sucrose, amino acids) from sources to where needed/stored (sinks)

Answer 73

Xylem: water+minerals. Roots>plant stem> leaves. upwards. physical, no energy. vessels- lose end walls forms continuous hollow tube. chemical lignin lining vessels (strength,support) -dead (so cells don’t take the water)

Answer 74

food substances produced by photosynthesis to where needed for processes(growing plant parts for immediate use, storage organs e.g bulbs + tubers, developing seeds) up and down stem. requires energy. translocation Adaption: living cells. Sieve tubes: no nuclei, perforated ends so cytoplasm connects one cell to the next Companion cells- attached to sieve tubes, provides energy. sieve tubes dependent on it’s companion cells.

Answer 75

High Air movement: removes water vapour from surrounding air =concentration gradient between leaf and air-increases water loss=water uptake increase, as water lost=more water pulled Blocked/closed stomata (coating, pollution, horticultural use).transpiration decreases=water uptake decreases. Blocks stomata pores=less water can lost by evaporation/diffusion through pores High light intensity: guard cells response to light intensity.high=turgid=bends=stomata opens, allow water lost High temperature- more kinetic energy=water molecules evaporate from mesophyll/diffuse faster. Humidity: decreases transpiration rate. Concentration of water outside leaf higher and gradient weaker when air more saturated with water vapour, less water lost as less diffusion.

Answer 76

Fill with water. cut shoot end under water, ensure xylem remains water filled, prevent air locks. Shoot inserted into rubber tubing. Potometer raised so air bubble taken up. potometer lowered into water. distance travelled by the air bubble record start and end locationJ over a set period of time Change the factor being tested. water reservoir = reset bubble (travels back to start), open tap below water reservoir. Repeat the experiment. rate of transpiration=distance moved/time Airflow: fan/hairdryer, blow air over plant Humidity- spray water in plastic bag, enclose the plant within it. Temperature: change temp of room w heater Light intensity: lamp/artificial lightning block stomata: smear leaf surface with petroleum jelly

Answer 77

Mass potometer- measure change in mass of a plant=water amount evaporated from leaves Bubble potometer- measures uptake of water by shoot, air bubble distance=measure of water amount lost by evaporation pulling water up to replace it

Answer 78

``` Receptors cells- detect stimuli, stimulate electrical impulses in response Coordinaration centre (brain, spinal cord/pancreas) - receives, processes info from receptors around the body Effectors- does responses to restore optimum levels. muscles and glands. Nerve cells=neurones. carry electrical impulses from one place to another ```

Answer 79

Long axon= can carry messages up + down body over long distances Tiny branches (dendrons), branch further=dendrites at each end. soma (cell body) axon (nerve fibre, conducts electrical impulses away from soma) dendrites (receive incoming impulses from other neurones). myelin sheath= fatty insulating layer around axon, allows nerve impulses to transmit more rapidly along, prevent signals from leaking. synapse between axon of one neurone and dendrite of another. bundle of neurones=a nerve

Answer 80

Sensory neurones- long dendrites, short axons Motor neurones- short dendrites, long axons Relay neurones- short dendrites, short/long axons

Answer 81

Dendrites- receives incoming impulses from other neurones, transmits electrical signals towards cell body(soma), covered in synapses, allows them to receive signals from other neutrons. Soma- maintains cell, keeps neurone functionaing efficiently. Enclosed by membrane(protects it+allows interact w surroundings). Contains nucleus-produces genetic information-directs synthesis proteins= vital for other parts of the neurones to function Axon- nerve fibre, tail-like structure. Joins the cell body at junction(axon hillock). Carries signals away from the cell body to the terminal to transmit electrical signals to other neurones. Ends at junctions (synapses). Myelin sheath- layer of fatty material that covers axons, prevent impulse of neurone interfering w another’s impulse.Speeds up conduction of nerve impulses along the axon/transmission to other neutrons. Protection. Made up of broken gaps called nodes of Ranvier. Electrical signals jump between nodes of ranvier which helps in speeding transmission of signals Axon terminals- Transmits signals to other neurone. At the end of axon terminal is a gap known as synapse. Holds vessels contain neurotransmitter-released from terminal into synapse-carry signals across synapse to other neurones. Electrical->chemical signals?Reuptakes excess neurotransmitters which did not get passed onto the next neurone

Answer 82

Central nervous system: brain, spinal cord Periperhap nervous system: nerves (branch off from spinal cord +extend to all parts of body)

Answer 83

Sensory receptors detect stimulus, info from receptors travels as electrical impulse Sensory neurones sends to relay neurones (located in the spinal cord of the CNS, bypassing the brain) The electrical impulses is passed from the relay neurone to the motor neurone. Motor neurones sends electrical impulses to an effector Effector produces a response (muscle contracts or gland secretion) There are synapses between neurones

Answer 84

electrical impulses travels along axon triggers synapses to release neurotransmitters diffuse across synapse, bind with receptor molecules on the membrane of the second neurone (receptor molecules bind only to specific neuronetransmitrers released) stimulates second neurone to transmit electrical impulse

Answer 85

Cerebral hemisphere, decision is made, nerve impulses are sent down the spinal cord to effectors via the motor neurones

Answer 86

``` Stimulus detected by sensory receptor. Impulse passes down sensory neurone Relay neurone in CNS passes impulse to motor neurone Motor neurone passes impulse to effector Muscle contracts/ gland secretes ```

Answer 87

Ciliary muscles: contract-change lens shape so focus near/ distant objects. Iris - ring of muscle controls how much light enters eye. Suspensory ligaments- connects ciliary muscles to lens Cornea- transparent window that lets light in. Refracts - bends light as enters eye Conjunctiva- protects eye Pupil- hole light passes through to hit the lens Lens- flexible transparent tissue, refracts light. Further refracts light to focus it onto retina. Optic nerve- Carries signal from retina to brain Fovea- area where see most of colour Retina- light receptors- which detect light that enters eye

Answer 88

Rod- more sensitive to light than cones. dim light | Cones- 3 which produces colour vision

Answer 89

Amount light entering reflex action, pupil size controlled by muscles of iris Dim light: radial contracts, circular relax. Dilated pupil, more light enters Bright light: Radial relax, circular contracts. Constricted pupil, less light enters

Answer 90

Accommodation - process of changing shape of lens to focus on near/distant objects Distant objects: Cililary muscles relax. Suspendory ligaments get pulled tight Lens thinner. Light is refracted less High muscle tension on lens Near object- Cililary muscles contract. Suspendonary ligameents loosen? Low Muscle tension on lens. Lens fatter. Light refracted more

Answer 91

Colour blindness Retina contains light receptor cells- cones sensitive to red,green,blue light. Colour blindness=lack of receptors/defects in them. No cure for inherited colour blindness. coloured filters make some colours stand out, may more confusing. Short and long sightedness- light not focus on the retina, clear image not formed Myopia (short sightedness) -cannot focus properly on distant objects Cause: elongated eyeball (distance between lens and retina is too great) -lens bring too thick and curved (light focuses in front of retina not on it) Overcome by: Placing Concave lens in front of eye (Glasses or contact lenses with concave lens) Hyperopia (Long sightedness) Cannot focus on near objects Cause: Eyeball being too short (distance between the lens and retina is too small) A loss of elasticity in lens- cannot become thick enough to focus Thin lenses- light focuses behind retina Overcome by: convex lenses Laser surgery- reshapes the cornea surgically Replacement lens- implanting articulated lenses in front of original lens through a small cut in cornea to correct an eye defect

Answer 92

Brain: - Controls complex behaviour - made up of billions of interconnected neurones and has direct regions that carry out different functions The brain is protected by the skull and is connected to the rest of the body through the spinal cord. It is part of central nervous system and contains many neurones

Answer 93

Has two cerebral hemispheres Left Hemisphere Logical, Language numbers, analytic thinking, problem solving Right Hemisphere- creativity Expression, emotional intelligence, imagination, intuition And the outer layer of the cerebrum is called the cerebral cortex

Answer 94

Cerebellum- controls balance, coordination of movement and muscular activity Medulla- controls unconscious activities such as heart rate and breathing rate Hypothalamus- regulating centre for temperature and water balance within the body. Also produces hormones which control pituitary gland.. control centre that monitors blood and helps maintain homeostasis Pituitary- stores and releases hormones which regulates many body functions. Controls activaties of other glands.

Answer 95

People suffering with brain damage may have reduced life expectancy People who live with brain damage as a result of injury are rare and are not always willing to take part in medical research Some people with severe brain damage may be unable to agree to the experiments and so their coldest relates may face the difficult decision of agreeing. Ethical issue which means people have religious or moral reasons. CT scans of brains cannot be used regularly as x ray radiation increases risk of cancer Patients must give consent for medical information to be shared Many case studies need to be analysed to draw reliable conclusions which is difficult if it is a rare condition or case Several areas of the brain may be involved in one specific function Some areas of the brain are difficult to access Many people believe testing on animals to investigate brain function is unethical

Answer 96

Highly specialised operation for treating brain. Not many doctors are able to do this, detailed and intricate work Difficult to easily access all parts of the brain during an operation Brain is delicate and Complex so difficult to treat, and carries risk of accidental damage. Mistakes here can lead to further brain injury causing irreversible damage to the surrounding areas The brain does not repair itself like other organs. Damage to the brain is often permanent Some brain damage can mean a change in consciousness. Or damage to other parts of nervous system, paralysis. The patient can enter a coma and become unconscious or remain conscious but enter a minimally conscious state where they require lifelong care Brain injuries due to surgery mistake can lead to - increased risk of epileptic fits - difficulty with coordination - hormonal problems if pituitary is damaged - losing smell and taste - changes in emotion or When nerves cells are lost, it’s permemnant the cells don’t grow back. Means treating nervous system damage can be difficult or impossible. More damage or side effects may be created after surgery is undergone, which could affect the patient’s quality of life

Answer 97

Human endocrine system is composed of glands which secrets chemicals (hormones) that gets carried in the bloodstream When the hormone reaches a target cell/organ. They alter the activity of specific target organs Once a hormone is used, it’s destroyed by the liver They can control the body and the effects are slower than the nervous system but they last for longer Pituitary gland in the brain- master gland

Answer 98

Thyroxine: Stimulates basal metabolic rate Controls speed oxygen/food products react to release energy

Answer 99

Adrenaline: Initiates fight or flee situation Increases heart rate and breathing rate Boosts delivery of oxygen and glucose to the brain and muscles Increases conversion of glycogen to glucose - so more energy released in muscles Diverts blood area from areas not needed for the fight or flee state (e.g digestive system) towards the muscles Increases flow of blood to muscles

Answer 100

Low thyroxine levels in blood stimulate hypothalamus to release TRH and this stimulates the pituitary gland to release TSH Which stimulates the thyroid to release more thyroxine and blood levels return to normal When thyroxine levels rise, it inhibits release of TRH from hypothalamus which in turn inhibits the release of TSH from pituitary so normal levels are maintained TRH= thyroid regulating hormone TSH= thyroid stimulating hormone Low thyroxine levels> TRH (hypothalamus) TSH (pituitary)>thyroxine (thyroid)

Answer 101

FSH (follicle stimulating hormone) -causes a egg to mature in the ovary LH (luteinising hormone)- causes ovulation (mature egg released from follicle) Oestrogen- causes the repair of the uterus lining, thickens Progesterone- maintains the uterus lining Testosterone- stimulates testes to produce sperm

Answer 102

-pituitary gland produces FSH FSH stimulates an egg cell to mature in an ovary and stimulates ovaries to release oestrogen - oestrogen causes uterus lining to repair itself and thicken and also stops FSH from being released by the pituitary gland so only one egg will mature, instead oestrogen stimulates the pituitary gland to release LH - When FSH falls, oestrogen eventually falls too LH peaks at around day 14 due to oestrogen and the egg gets released from the ovary (ovulation) The empty follicle left from the release of the egg (corpse luteum) releases progesterone Progesterone maintains the uterus lining for the implantation of the egg progesterone inhibits LH so only one egg is released per cycle If a fertilised egg is not received by the uterus lining, the levels of progesterone falls The uterus lining breaks and leads to menstruation Low levels of oestrogen and progesterone causes FSH to not be inhibited anymore and the cycle starts again If the egg is fertilised, progesterone production continues

Answer 103

Hormonal contraceptives- oestrogen and progesterone-inhibits FSH and LH production. eggs cannot mature/release. Preventing pregnancy. Thickens mucus in cervix, keep sperm from reaching egg

Answer 104

Hormonal: Oral contraceptives: -side effects: changes in weight/mood/blood pressure (high levels of oestrogen) -reduce risk of certain cancers Contraceptive injections/implants Skin patches (Contains slow release progesterone to inhibit maturation +release of eggs)

Answer 105

. Non-hormonal methods: Physical barrier(condoms and diaphragms)- prevent sperm from reaching egg Condoms:easy and quick to use. tear or rip Diaphragms- need to be put in before sex and left in for several hours afterwards Intrauterine devices (IUD coil): prevent implantation of embryo/release of a hormone - risk of ectopic pregnancy (where egg implants somewhere outside of uterus) - can remain in position for up to 10 years - needs to be fitted by a health professional Spermicidal agents- kills/disables sperms - allergic reaction may happen - can be added alongside physical barriers (e,g condom) Abstaining from intercourse when there is a egg in the oviduct -if timings are not accurate, chance of pregnancy is high Surgical methods- male/female sterilisation (e.g vasectomy where sperm ducts are cut and tied) - cannot be reversed - permanent method

Answer 106

Fertility drugs - FSH+LH to stimulate eggs to mature in the ovary. Some women difficulty in fertility= not enough FSH. Increase pregnancy chances -increases chance of multiple pregnancies in Which could lead to premature or underweight babies Or death of mother . In-vitro fertilisation treatment -involves giving a mother FSH and LH to stimulate maturation of eggs in the ovary - eggs are collected from the mother and fertilised by sperm from the father in a dish in the laboratory - fertilised eggs develop into embryos - one or two embryos are inserted into the mother’s uterus Advantages- Allow people to have babies when there are body conditions that don’t allow them to -embryos can be screened for genetic diseases so only unaffected embryos are inserted into the womb -unused eggs can be used for research or donated to other couples Disadvantages: Side effects from the drugs used (severe headaches) -possibility of multiple births -too many eggs develop -emotional and physically stressful -success rates are not high -ethical concerns (couple only want certain babies with desirable qualities) -embryos not used may be destroyed (viewed as killing new lives)

Answer 107

They act as messages from one part of the plant to another They control the rate of cell elongation, germination, flowering, development and ripening of the plant’s fruits, dropping of the fruit and shedding of leaves

Answer 108

``` Auxins: -change the rate of cell elongation For high concentration of auxins: -cells in shoots grow more -Cells in roots grow less ```

Answer 109

Gibberellins: - ends seed dormancy (initiates seed germination) - increase speed of germination - stimulate cell elongations (plants grow taller) - promotes flowering - increase fruit size Ethene: - speeds up fruit ripening in plants - controls cell division during plant growth

Answer 110

Auxins: - selective weed killers (causes weed to grow too quickly and die). Auxins concentration higher on broader leaves and most weeds have broader leaves. - rooting powder. Makes stem cuttings develop roots quickly - promoting growth in tissue culture. Stimulates cell division and elongation to grow whole plants from small sections of a parent plant Auxin or gibberellin: Growing seedless fruits. Spray the flower with hormones so fruit develops without the egg cells being fertilised in flowers therefore seeds don’t develop in the fruits. Parthenocarpic fruit development (development of fruit without fertilisation to produce a seedless fruit) Gibberellins: Breaking seed dormancy. So it can germinate at all times of the year

Answer 111

Homeostasis: the maintenance of a constant internal environment in the body -human enzymes work best at 37oC (human body temperature) and they catalyse vital chemical reactions in the body Low temperatures can cause hypothermia and death High temperatures can cause dehydration, heat stroke and death Low temperatures cause enzymes to have a slower rate of reaction- less kinetic energy and slower movement = less successful collisions High temperatures causes enzymes to denature It maintains optimism conditions for enzyme action and all cell functions If conditions are outside of a specific optimum range, enzymes cannot function and it leads the organism to die

Answer 112

When the body temperature changes, the brain sends nerve impulses to the skin The skin has hairs, erector muscles, muscles, sweat glands which helps it in the 3 ways it has to decrease/increase the heat loss hair erector muscles contract which raises the skin hairs Hairs on the skin trap air for insulation when standing up- to decrease heat loss. When lying flat there’s less air trapped and heat escapes- to increase heat loss These tiny muscles in the skin can pull up by contracting or lay down the hairs by relaxing when it’s too hot or cold

Answer 113

Sweating and shivering Glands under the skin secrete sweat onto the surface- to increase heat loss by evaporation When liquids evaporate from surfaces they cool the surfaces Shivering- involuntary repeated rapid contraction and relaxation of muscles to quickly release energy from glucose in respiration so some of this energy is released as heat to warm up

Answer 114

Vasodilation: blood vessels that carry blood to the skin dilates. Blood flow in skin capillaries increases. Arterioles get wider. more heat is carried by the blood to the skin. More heat lost to the air by radiation Vasoconstriction- blood vessels shrinks down. Arterioles narrow. Blood flow in skin capillaries decrease. Less heat carried by the blood to the skin. Reduces heat loss.

Answer 115

When blood glucose levels high, pancreas produces insulin Causes more glucose to move from the blood into the cells In liver cells, excess glucose converts into glycogen for storage in liver and muscles Blood glucose levels decrease When blood glucose levels low, pancreas does not produce insulin. Less glucose is absorbed into the cells So glucose is not converted into glycogen. And blood glucose levels don’t don’t decrease

Answer 116

When blood glucose levels high- insulin send signal to liver, muscles and other cells to store excess glucose in the form of glycogen When blood glucose level low- glucagon causes the liver to convert glycogen to glucose.

Answer 117

Type 1- Pancreas doesn’t produce enough insulin - immune system attacks pancreas, destroying the cells that produce insulin -uncontrolled high blood glucose levels -treatment by injecting insulin -can help control their blood glucose level by exercising (increases respiration in muscles therefore lowering blood glucose levels) and dieting (not eat foods that will largely increase blood sugar levels) Type 2- The body cells no longer respond to insulin produced by pancreas -high blood glucose levels -can be controlled by carbohydrate controlled diet and exercise regime Carbohydrate is digested into glucose which can raise overall blood glucose levels Exercise increases respiration in muscle therefore lowering blood glucose levels -insulin injections can be given in severe cases of type 2

Answer 118

Hypotonic- turgid/bursting Isotonic- flaccid Hypertonic- plasmolysed/shrivelled Haemolysis-bursting

Answer 119

Contains nephrons which remove excess Produces urine Kidneys control the loss of excess water, ions and urea to maintain water levels water, mineral ions and urea from the blood

Answer 120

**describe the gross structure of the kidney and the structure of the kidney tubule ** Renal vein carries deoxygenated blood away from kidneys Renal artery carries oxygenated blood to the kidneys Glomerulus ( branched capillary network) in kidney filters blood that arrives through renal artery- removes water, glucose, salts and urea from blood. Proteins are too large to pass through so it remains in the blood. There is high pressure here to aid in the ultrafiltration. Filtered blood returns to circulatory system through renal vein after being filtered The waste substances pass from the capillaries into the glomerulus into the bowman’s capsules. Then the substances move from bowman’s capsule towards the loop of henle. Kidneys reabsorb molecules needed in the proximal convoluted tubule (all glucose + any water needed to maintain a balance of water level in blood plasma +any ions needed to maintain a balance of mineral ions in blood plasma). Waste substances that haven’t been selectively absorbed move from loop of Henle to distal convoluted tubule to the collecting duct as urine The urine passes through the ureter to the bladder where it is stored, then the urine is carried out of the body by the urethra

Answer 121

``` Renal artery Renal vein Medulla Renal pelvis Cortex Ureter ```

Answer 122

``` Renal artery and renal vein Glomerulus Bowman capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct ```

Answer 123

Causes kidney tubules to be more permeable so it reabsorbs more water

Answer 124

Osmoregulation Hypothalamus detects the changes of concentration of water in the blood plasma. If there is too little, the pituitary gland releases more ADH which causes the kidney tubules to be more permeable and selectively reabsorb more water so less water is lost in urine, Vice versa, if there is too much, the pituitary gland releases less ADH so less water is reabsorbed by the kidneys and more water is lost in urine. So blood water levels returns to normal Different temperatures: Hypothalamus monitors the temperature of the blood And imitates homeostatic responses when the temperature is too high or low When too low: shivering, vasconstriction, hair erector muscles contract, skin hairs raised When too high- sweating, vasodilation, hair erector muscles relax so hairs flatten

Answer 125

Nitrogen: Nitrogen gas in atmosphere converted to nitrates in soil by nitrogen-fixing bacteria. nitrates and ammonia absorbed by plants to make plant proteins. Plants eaten by animals and they make animal proteins, contains nitrogen. excretion and egestion- animal processes. Animal dies, decomposers break down corpse, urine(from excretion) and faeces(from egestion), results in nitrogen returning to soil as ammonia. Ammonia converts to nitrate by nitrifying bacteria. Denitrifying bacteria convert nitrates to nitrogen gas. Carbon- Carbon dioxide in atmosphere absorbed by producers for making glucose in photosynthesis. Animals eat plants, passing the carbon compounds. Animals eat animals passing carbon compounds along food chain. Animals and plants aerobic respire, releasing CO2. Animals and plants die. Decomposers break down the dead bodies, return carbon to atmosphere as CO2- decomposers aerobic respire which releases CO2. When decomposition is blocked, fossil fuels form. Combustion of fossil fuels release CO2 to atmosphere Water -evaporation. Energy from sun evaporates liquid water from all places (e.g ponds, lakes, land, oceans) to water vapour. Condensation- as water vapour rises, the atmosphere temperature cools and the water condenses from gas to tiny drops of liquid, forming clouds. Precipitation-water droplets in clouds get heavy and the water falls as rain/snow/hail/sleet surface run off- if a large volume falls/ground is already wet, some water runs along the surface of the ground to nearby water Percolation/Infiltration- when water absorbs into the ground, trickles deeper through gaps into the soil, and stored within underground rocks called aquifers Transpiration- plants allow some water it has to evaporate as vapour from leaves to continuously pull more water. Some water gets absorbed by plants through roots .

Answer 126

Nitrifying bacteria- converts nitrogen gas in atmosphere to nitrates in soil Denitrifying bacteria- converts nitrates back to nitrogen gas Nitrogen fixing bacteria- converts ammonia to nitrates Decomposers help return minerals and nutrients back to the environment so then the materials can be used by other organisms. When they break down dead plants and animals, the nitrogen is released back as ammonia in soil As bacteria and fungi decompose dead matter, they respire and release carbon back to environment as CO2

Answer 127

Carbon cycle Carbon dioxide needed in Photosynthesis to make glucose for producers Glucose important for chemical reactions in organisms For production of DNA, skin, enzymes, nerves, fats, proteins and all organic compounds. Every living organism has carbon compounds. . . Water cycle: Water is important for maintaining habitats, allowing nutrients to flow between organisms and environment, survival of organisms Plants use water in photosynthesis to make glucose Regulates body temperature in humans Dissolving waste substances and carrying them out of the body in urine, faeces and swear For dissolving vital nutrients in bloodstream and delivering to cells

Answer 128

Temperature High temperatures denature enzymes, stopping enzyme activity and killing decomposers and therefore preventing decomposition. Decomposers need enzymes to break down the dead matter so they can absorb it. Low temperatures slow the rate of reaction of enzymes and prevents growth and reproduction of microorganisms, slows rate of decomposition. Oxygen availability- Oxygen needed for aerobic respiration by decomposer microorganisms, without oxygen microorganisms will die. Some bacteria can survive - bacteria that anaerobically respire. Slows or prevents decomposition Water content- Lack of water slows or prevents decomposition. Water needed for transport and to support reactions inside microorganisms. Decomposers need water to digest their food. Without water, microorganisms will die.

Answer 129

Individual organisms- any living thing or organism. A single member of a species. Species- individuals do not breed with individuals from other groups Populations- all members of a single species that live within a geographical area Communities- all the organisms that live within a habitat Ecosystem- living organisms (biotic) in particular area together interacting with non living components of environment (abiotic)

Answer 130

Abiotic factors Light intensity: Light needed by plants for photosynthesis. More light=increase rate in photosynthesis, increase plant growth rate. Different plants, different optimum light intensity. Temperature- affects rate of photosynthesis in plants and enzyme activity in organisms. Different organisms, different optimum temperatures Moisture levels- plants and animals require water to survive for important chemical reactions and transporting soluble substances. Waterlogged soils can kill plants as there is little oxygen so cells in roots unable to respire- although some plants grow best in high moisture levels e.g pitcher plants. PH of soil- different plants have different optimum pH levels. pH further from optimum level can decrease enzyme activity/reaction rate of enzymes or denature enzymes in organisms Wind intensity-wind speed affects transpiration rate. Transpiration affects photosynthesis as it ensures water and mineral ions are transported to the leaves (as water evaporates from leave surface, ensures more water can be continuously pulled to plant) Carbon dioxide levels- CO2 required for photosynthesis. Affects rate of photosynthesis Oxygen levels (for aquatic animals)- some aquatic animals can only survive in water with high oxygen concentrations

Answer 131

Availability of food- more food means organisms have a higher chance of surviving and reproducing and their populations can increase Presence of new predators- balanced communities have predators catching enough prey to survive but not so many that they wipe out their prey population. The prey is adapted to predators. If a new predator is introduced, it may cause imbalance in the community as the prey would not be adapted to the new predators and their numbers would decrease more rapidly as the new predators would be advantageous. Competition between organisms- if two species compete for the same resources and one is better adapted, then that species will outcompete the other. This way continue until there are too few members are the lesser adapted species New pathogens- if a new pathogen enters a community, the population living there will have no immunity or no resistance or it and the population decreases

Answer 132

Interdependence:all organisms in an community rely on each other for food, protection, shelter, etc for survival. Predator prey cycles. Cyclical change (when prey increases, predator increases and prey decreases, when prey decreases, predator decreases and prey increases). Any change in numbers of prey affects numbers of predators and vice versa. If one side were to be drastically affected, it greatly influences the other side (e,g introduction of new predators) Mutualism- organisms relying on other organisms of a different species for the benefits of both. E.g nitrogen fixing bacteria and leguminous plants. Parasitism. Parasitic organisms that live in/on a host, the parasitic organism benefits from it and the host suffers. E.g tapeworms Competition: keeps the balance of ecosystem by keeping populations in balance. Plays a role in evolution. Animals compete for food, water and territory. Plants compete for sunlight, water, mineral salts, space. Organisms compete for resources that they need to survive within a community.

Answer 133

First tropic level: producers- photosynthesis using light energy from sun to make glucose. Provides all the biomass for the food chain Second tropic level- primary consumer. herbivore or omnivore. Eats producers. Third tropic level- secondary consumer. Carnivore or omnivore. Eats primary consumer Might be additional consumers (e,g tertiary and quaternary). Final tropic level is called apex predator. Top of the food chain and has no predators

Answer 134

Biomass is transferred along the food chain ``` The rest is used to complete life processes: Excretion Respiration Egestion Movement And so on ```

Answer 135

Biomass is steadily lost as it is transferred along the food chain Food chains are usually not long as biomass transferred decreases the longer the food chain as the total amount of biomass transferred becomes very small after a few tropic levels. Only *around* 10% of biomass is transferred from each tropic level to the next every time Percentage effiency transfer = (biomass in higher trophic level/ lower trophic level ) x100

Answer 136

specialised sex cells that have half the number of chromosomes

Answer 137

Chromosome: organisation of DNA into tightly packed coiled strands

Answer 138

small section of dna that codes for a particular sequence of amino acids to make a specific protein

Answer 139

Genome: entire genetic material of an organism. The genome and its interaction with the environment influences the development of the phenotype of an organism e,g weight.

Answer 140

different form/version of a gene

Answer 141

always expresses in phenotype itself when present, only one allele is needed

Answer 142

both copies of the recessive alleles need to be present to be expressed in the phenotype

Answer 143

Homozygous: two identical alleles for the same characteristic

Answer 144

two different alleles for the same characteristic

Answer 145

collection of alleles that determine the characteristics of an organism (expressed as a phenotype)

Answer 146

the visible characteristics of an organism

Answer 147

All genetic variants arise from mutations Mutation is a random change in the gene or chromosome Most have no effect on phenotype Some influence phenotype a very few fully determine phenotype

Answer 148

Mutations in coding DNA Sequence of DNA could be changed Changing the DNA sequence can change the amino acids that make up the proteins Enzymes are made of proteins and they have a specifically shaped active site If a mutation happens in the coding DNA that codes for the enzyme then the wrong amino acids could be used to make the enzyme which changes the shape of the enzyme’s active site and the enzyme will not work properly Mutations in non-coding DNA Non coding parts of DNA can switch genes off and on When genes are switched off, the process of transcription stops which means no mRNA is being made for that gene and therefore no protein can be made for that gene So a mutation in non coding DNA may affect gene expression and whether the correct protein is synthesised or not

Answer 149

Sexual reproduction Advantages: - genetic variation - species can adapt to new environmental change - a disease is less likely to affect all individuals in a population Disadvantages: - time and energy needed to find a mate - both parents need to be fertile - not possible for a isolated individual to reproduce

Answer 150

Asexual reproduction Advantages: - population can increase rapidly if conditions are favourable - only one parent needed - more time and energy efficient - faster than sexual reproduction Disadvantages: - no genetic variation, all offsprings genetically identical - disease may affect all individuals in a population - species may only be suited to one habitat - not adapted for change

Answer 151

Haploid: gamete that contains one set of chromosomes. Has half the total number of chromosomes that an organism needs to develop Diploid: cell that contains two sets of chromosomes, has total number of chromosomes needed to develop

Answer 152

Nuclei of gametes fuse to create a zygote The half chromosomes cross and when the gametes combine in fertilisation they create a embryo with the full set of chromosomes Meiosis role is so the end result, The embryo Has the full correct set of chromosomes after the two gametes combine with their half number chromosomes

Answer 153

The inheritance of traits controlled by a single gene with two alleles

Answer 154

Human body cells have 23 pairs of chromosome 22 pairs are autosomes, controls characteristics The last one pair carries genes that determine sex Males have X and Y sex chromosome Females have two X chromosomes 50% chance of female offspring, 50% chance of male offspring

Answer 155

Most phenotypic features are the result of multiple genes rather than single gene inheritance Some characteristics are controlled by a single gene however most characteristics are caused by the interaction of many genes

Answer 156

Before Mid 18th century Gregor Mendel Studied the inheritance of different characteristics In pea plants And flowers He discovered that: When he bred red flowered plants with white flowered plants, all the offsprings had red flowers If he bred these red flowering plants with each other, most of the offspring had red flowers, but some had white flowers. Mendel’s idea: The inheritance of each characteristic is determined by “units” that are passed onto descendants changed Mendel’s work expanded our knowledge of genetic inheritance before DNA had been discovered The idea that genes were located on chromosomes emerged in the late 19 century - better miscoopes and staining techniques allowed scientists to visualise the behaviour of chromosomes during cell division In early 20th, observation of chromosomes and Mendel’s units behaved in similar ways Led to theory that the units (now called genes) were located on chromosomes In mid 220, James Watson and Francis Crick worked out structure of DNA and modelled it using data from Rosalind Franklin Showed that bases occurred in pairs And the x ray data showed that there were two chains wounded in a double helix 21st century Entire human genome was sequenced Now scientists are working out the functions of our different genes And gene therapy is being developed

Answer 157

There is usually an extensive genetic variation within a population within a population of species

Answer 158

As more scientific equipment such as microscopes with higher magnification become available It allowed scientists to examine organisms in more detail and note important features Such as the identification of sex organs which allowed more divisions in the classification system to be created Helped to develop Linnaeus’ classification system - use of microscopes - studies of biochemistry - dna evidence Originally: artificial classification - purely on human obversvatiom to compare characteristics of different organisms Development of microscopes allowed cells to be examined in more detail and organelles within distinguished So more scientific approach to classification Natural classification: Phylogenetically (study of how related organisms are) helped to work out how species evolved from one another, molecular phylogenetic - comparing molecules inside organisms to see how similar they are. Developments in biochemistry- scientists can work out how similar organisms are on a molecular level E.f comparing structure of proteins used in aerobic respiration between organisms Comparing DNA sequences of different organisms - species that are more closely related likely to have fewer differences in the sequence of their dna bases Allowed classification to be developed , Theee domain system by Carl System based on evidence from analysing organisms on molecular level

Answer 159

Genetic variation in population due to mutations. Organisms better adapted to environment will survive and reproduce. So Advantageous alleles of variant organisms are passed on offspring. Over many generations, process of natural selection leads to evolution.

Answer 160

Evolution is a change in the inherited characteristics of a population over time through the process of natural selection which may result in the formation of new species

Answer 161

Fossil- preserved remains of dead organisms from millions of years ago - Hard body parts - e.g bones/shells. They don’t decay easily/they decay slowly so can be replaced by minerals as they decompose, leaving fossils - Parts of organisms that have not decayed due to the absence of conditions needed for decomposition. E.g dead animal trapped in ice - preserved traces of organisms. E.g footprints which become covered by layers of sediment and eventually becomes rock Fossil remains have been found in rocks of all ages Fossils of the simplest organisms - found in oldest rocks Complex organism fossils- in newest rocks Supports that simple life forms gradually evolved into complex ones

Answer 162

Bacteri can evolve quickly Cuz they reproduce fast Mutations in dna of bacteria can produce new characteristics Random mutation may cause some bacteria to become resistant to certain antibiotics- mutation protects bacterial cell from effects of antibiotic Antibiotics kill bacteria that are not resistant but anti biotic resistance ones survive and can reproduce with less competition from non resistant bacterial stains Genes for antibiotic resistance are passed on to offspring the anti resistant bacteria grow in population and overtime then whole population is antibiotic resistance because the antibiotic resistant bacteria were best suited to their environment Example of natural selection leading to evolution

Answer 163

Darwin Studied variation in plants, animals and fossils During a 5 year voyage around the world On the ship HMS beagle Studies finches during his five week visit to the Galápagos Islands Proposed that Individual organisms within a particular species show a wide range of variation for a characteristic Individuals with characteristics most suited to the environment are more likely to survive and breed successfully The characteristics that have enabled these individuals to survive dare then passed onto the next generation Theory of natural selection Wallace Travelled the world Studying warning colouration in animals Includes Golden Birdwing Butterfly Theory of speciation (formation of new and distinct species in the course of evolution due to separation and isolation) Made his own theory of evolution separate to Darwin Darwin and Wallace gathered and combined their research- joint writings 1858 And presented papers on their theories to the Linnaean Society Which didn’t receive much attention And following year, Darwin published On the Origin of Species book

Answer 164

Incorporated into modern theory of biological evolution Used to study migratory and evolutionary history And past history of how organisms evolved

Answer 165

Quadrat (abundance) Transect (for distribution) Random sampling using a Place quadrat at random coordinates Count the number of organisms in the Repeat steps Calculate total area of one Find total area of habitat being sampled Calculate mean number of organisms per quadrat by calculating the mean from the number of organisms counted from the quadrat divided by the number of Times the quadrat was placed down Transect Quadrat placed at regular distances, e,g every five meters Along a line called transect To link changes in distribution due to abiotic factors such as light intensity To link changes in distribution due to abiotic factors such as light intensity

Answer 166

Land Pollution, air pollution, water pollution, noise pollution, increased waste, deforestation, peat hog destruction, global warming due to CO2 emissions. Land being cleared for human uses. Hedgerows being removed. Hunting. Destruction of habitats. Introducing predators and invasive species to other places. Conservation and species and habitats by charities, governments and individuals (conservation projects) Breeding programs for endangered species Protection and development of new endangered habitats Replanting hedgerows Reducing deforestation and release of greenhouse gases Recycling rather than dumping waste in landfills. Illegalising poaching and hedgerow removal. Seed banks. Areas protected from exploitation set. Afforestation, education. Selective logging. Monitoring using satellites to check no illegal activities are taking place (wide deforestation)

Answer 167

Land being cleared for human uses for building, quarrying, agriculture and waste disposal (landfill) Area of rainforest being cut down reduces biodiversity Land use for farming No shelter/food The hedges used to make boundaries of the fields can get in the way of machinery So farmers remove the hedgerows To allow for more easier harvest However hedgerows provide lots of biodiversity They provide food and shelter for a range of animals Birds rely on hedges for their nests and to raise offsprings safely hidden from predators Hedgehogs and mice also use it to nest, shelter and hibernate Without hedges these organisms suffer and numbers may decline which has a knock on effect on the rest of the ecosystem Deforestation: Humans have been deforesting woodlands to build houses, get wood materials and agriculture Deforestation destroys the habitats of organisms that live in it Therefore This kills individuals of many species No shelter/food Hunting of endangered species Poaching of organisms bringing organisms to close extinction Overhunting of organisms for food can reduce species numbers Pollution More fossils fuels being burnt for heat and power More food being grown Land taken over for industry and housing Air pollution- combustion of fossil fuels + others contributes to greenhouse effect and leads to global warming Melts polar ice caps and colder places - polar bears Also releases soulful dioxide and nitrogen oxides which causes acid rain Acid rain removes minerals and nutrients from soil that plants need Increase in pH with heavy acid rain downpours can kill or injure plants On fish and wildlife, organisms that are sensitive to pH. At pH 5, most fish eggs cannot hatch High pH may lead fishes to die Water pollution Fertilisers Eutrophication Algae bloom and decrease in oxygen levels Kills aquatic organisms s Pesticides Blown in streams and rivers Eaten by organisms Bioaccumlation up food chain Kills organism at top of food chain Due to the accumulation of the toxic pesticide Higher concentrated lethal dose Greenhouse effect Global warming Carbon dioxide, water vapour and methane Released from combustion Global warming, melting of polar ice caps, overall temperature increases which includes ocean temperatures New climate patterns, Habitat loss, Altered competitive relationships, Invasive species, Due to migration due to habitat loss, Disrupt the match between organisms and local environment, Reducing survival and reproduction

Answer 168

Conversation projects Benefits Maintains biodiversity- more species can survive. Food chains and interdependence, species rely on others for survival. Ecotourism- tourism contribution to preservation and provides funding for project Knowledge- some unknown species may become extinct before discovering them. Important to know their importance in the ecosystem and any unique traits of the organism that may help in other fields of research e.g medicine Medicines - conserving ecosystems means potential to uncover new drugs in plants that may allow us to treat more diseases Challenges: Conservation costs money, Must be able to raise enough money to carry out conservation Lack of understanding - eduction and outreach programmes needed to educate people on the importance of conserving, Monitoriarion of it: difficult to monitor the effect of any conservation scheme if it actually has positive effect, Changing laws and legislations p- takes time as legal documents have to pass through a lot of comities before they become the law and the situation could worsen during it.

Answer 169

Pollution indicators Intricately species - presence, abundance or absence of these organisms provides information of the pollution in the environment Water Some freshwater animals are sensitive to oxygen levels e.g stonefly larvae and freshwater shrimps If these animals are found in the environment area, shows that no pollution and irs clean However some organisms are adapted for surviving in polluted conditions. E,g blood worms and sludge worms. Presence of these indicates there is high level of water pollution No pollution- mayfly larva and stonefly nymph Some pollution- no mayfly larva or stonefly nymph but freshwater shrimp and cad is fly larva still Moderate- bloodworm and Waterhouse High- sludge worm and red tailed maggot Very high- no living organisms Air: Busy lichens need very clean air Leafy lichens can survive a small amount of air pollution Crusty lichens can survive in more polluted air

Answer 170

Food security Ability of human populations to access affordable food of sufficient quality and quantity. Measure of how much food there is, the quality and whether people can access it Biological factors that affects it Increase in human population, birth rates are increasing and more better access of medical care so less death rate Changing diets, scare food resources are transported to be sold to other areas from areas which need them. Wealthier countries tending to eat more meat which is more energy intensive to produce than plant-based foods. New pests and pathogens- attacks crops and farm animals. And can evolve. Environmental changes - global warming, climate change. More droughts and less crop yield. This may be counteracted by increase yield due to higher carbon dioxide concentrations Prices of foods increasing and increased oil prices could affect the production and distribution of food Increased costs of farming

Answer 171

Hydroponics: An extreme form of growing crops in glasshouses is called hydroponics. Soil is replaced by a mineral solution pumped around the plant roots.Removing the soil means there's no risk of soil organisms causing disease but the plants have to be supported.Monitoring and adjusting the concentrations of minerals in the solution enable the grower to control growth. Hydroponics allows crops to be grown in regions where there's little or no soil. Due to the costs involved, hydroponics is used only for high-value crops. Intensive farming- growing high yield crops, adding fertilisers, battery farming, herbicides and pesticides. Pesticides, insecticides, herbicides, fungicides- to get rid of pests which may decrease plant yield and rid of weeds and other plants which may provide competition over resources for desired crops. Fungicides to kill fungi diseases on plants that decrease crop yield. Insecticides to kill insects( which feed on/live on/damage plants and reduce their quality/causes plant to die.) Biological control-releasing a natural predator into the crop growing area, the number of pests can be reduced. Artificial environments- Some food products have been grown in artificial environments to increase productivity. Examples include growing tomatoes in glasshouses and salmon in fish farms. Selective breeding- humans breed plants and animals for particular genetic characteristics that increased yield or quality Genetic engineering- modifying the genome of an organism by introducing a gene from another organism to result in a desired characteristic for increased yield or quality Biotechnology - novel foods - novel food that are recently introduced or produced usinf new process. E.g fermenters to produce fungus to collect and purify to produce proteins Fertilisers- increase plant growth and yield, and quality. Replenishes minerals taken from plants to soil for new plants.

Answer 172

new varieties may be economically important, by producing more or better quality food animals can be selected that cannot cause harm, for example cattle without horns reduced genetic variation which can lead to attack by specific insects or disease and could be extremely destructive rare disease genes being unknowingly selected as part of a positive trait, leading to problems with specific organisms, eg a high percentage of Dalmatian dogs are deaf the creation of physical problems in specific organisms, eg large dogs can have faulty hips due to not being formed correctly future generations plants and animals will all share very similar genes which will reduce variation. Genes and their different alleles within a population are known as its gene pool. Inbreeding can lead to a reduced gene pool, making it more difficult to produce new varieties in the future. This also makes organisms prone to certain diseases or inherited defects.

Answer 173

genetic engineering is a process which involves modifying the genome of an organism to introduce desirable characteristics

Answer 174

selection of the desired characteristic the gene responsible for the characteristic is 'cut out' of the chromosome. Restriction enzymes are used to isolate the required gene from the chromosome. They cut the DNA at a specific sequence. Restriction enzymes leave sticky ends that are overhangs of DNA. the gene is transferred and inserted into another organism. A vector is needed to get the gene into the host cell. This is usually a plasmid that is taken from a bacterial cell. The plasmid is cut with the same restriction enzymes so it gets the same sticky ends. The sticky ends on the plasmid stick with the ones on the gene. The gene and the plasmid are joined together using an enzyme called DNA ligase. The vector is transferred back into the bacteria host cells. The host cells now have a gene from another organism and so are said to be transgenic. replication of the modified organism

Answer 175

Benefits of genetic engineering: Genetic modification is a faster and more efficient way of getting the same results as selective breeding. Improve crop yields or crop quality, which is important in developing countries. This may help reduce hunger around the world. Introduce herbicide resistance, which results in less herbicides being used, as weeds are quickly and selectively killed. Insect and pest resistance can be developed and inserted into the plants. The plant produces toxins, which would discourage insects from eating the crop. Sterile insects could be created such as a mosquito. They would breed, which would lead to infertile offspring. This may help reduce the incidence and spread of diseases, such as malaria, dengue fever and the Zika virus. Risks of genetic engineering: Transfer of the selected gene into other species. What benefits one plant may harm another. Some people believe it is not ethical to interfere with nature in this way. Also, GM crop seeds are often more expensive and so people in developing countries cannot afford them. GM crops could be harmful, for example toxins from the crops have been detected in some people's blood. GM crops could cause allergic reactions in people. Pollen produced by the plants could be toxic and harm insects that transfer it between plants.

Answer 176

Agricultural solutions: Selective breeding Decide which characteristics are important enough to select. Choose parents that show these characteristics from a mixed population. They are bred together. Choose the best offspring with the desired characteristics to produce the next generation. Repeat the process continuously over many generations, until all offspring show the desired characteristics. Restriction enzymes are used to isolate the required gene leaving it with sticky ends. Sticky ends are short strands of unpaired bases. A vector, which is usually a bacterial plasmid or a virus, is cut by the same restriction enzyme leaving it with corresponding sticky ends. The vector and the isolated gene are joined together by ligase enzyme. The vector inserts the gene into required cells. The genes are transferred to animal, plant or microorganism cells, during early development, which allows them to develop with the desired characteristics. Genetic modification Intensive farming Intensive farming is a series of techniques that maximise the yield of animal or plant crops. Examples of intensive farming are shown in the table below. Remove competing plants from the crop growing areaHerbicide sprayAllows more energy to be transferred to the cropReduces biodiversity. May have harmful effect on health. Remove animals that feed on the cropPesticide sprayPrevents energy being transferred from the crop to consumersReduces biodiversity. May poison helpful organisms. Keep animals indoors'Battery' farmingReduces energy transferred to environment so more energy available for growthIncreased risk of disease. Lower quality product. Ethical concerns. Producing maximum food product yield using minimum space by use of inorganic fertilisers and pesticides to aid plant growth and reduce loss. Maximising animal growth rates and minimising labour inputs by mechanisation Biological control is an alternative to using pesticides. By releasing a natural predator into the crop growing area, the number of pests can be reduced. This can have unforeseen consequences as the numbers of different organisms in the food web are changed. There have been examples of the predator becoming a more serious pest than the original problem. Biotechnology Development of novel foods could aid in meeting the food demand of the growing human population. A good example of this is the fungus Fusarium which is used to produce mycoprotein . The fungus is grown in large containers called fermenters. The conditions inside are maintained to promote maximum growth: the pH and temperature are maintained at the optimum level the temperature is controlled by a water jacket that surrounds the whole fermenter sterile oxygen is added to make sure that aerobic respiration occurs a food source like glucose syrup is added the mixture inside is stirred to make sure all the oxygen and nutrients are equally distributed Stainless steel with water jacket and paddles. Steam and nutrients enter at top. Cooling water and air at bottom. Exhaust at top right. Cooling water leaves near top. Outlet for the product at base. Diagram of a fermenter After the fungus has fully grown in the fermenter, it is harvested and purified and the process is then repeated with a new batch of ingredients. Producing protein from fungus is much more efficient than producing meat from livestock. Only about 10% of the energy found in grass is transferred to animals like cows that eat it. 1000 g of plant carbohydrate can produce up to 14 g of beef, 49 g of chicken or 136 g of mycoprotein. Additionally, fermenters can be used to produce protein in places where grass and livestock cannot grow.

Answer 177

Health is the state of physical, mental and social well-being. It is not just being free from disease . Factors can work together to affect physical and mental health. Diseases stop part of the body from working properly.

Answer 178

communicable, or infectious, which can be transferred from one person to another, or from one organism to another, eg in humans, these include measles, food poisoning and malaria non-communicable, which are not transferred between people or other organisms, eg cancer or Type 1 diabetes

Answer 179

For instance, human immunodeficiency virus (HIV) infections, which lead to AIDS, affect the efficiency of the immune system. This means people with HIV and AIDS get more infectious diseases than a healthy person. A common infectious disease that occurs in HIV patients is tuberculosis. Tuberculosis is a bacterial infection, mainly affecting the lung Viruses living in cells can be the trigger for cancers. For instance, the majority of cases of cancer of the cervix are linked with a virus present in the female reproductive system called HPV. The reaction of the immune system to pathogens and other foreign bodies can trigger allergic reactions that lead to skin rashes and asthma. For instance, severe respiratory infections in babies can lead to asthma in later childhood. Severe physical ill health can lead to depression and other types of mental illness.

Answer 180

``` Animals Direct contact Body fluids transfer Water Air Unhygienic food preparation Vector Plant Wind Direct contact Farmers Herbivores and omnivores eating plants Rain Insects ```

Answer 181

``` Animals Sterilising water Antiseptics Sterilising surfaces- suitable hygiene personal Suitable hygiene in foods- cooking foods thoroughly and preparing them in hygienic conditions Vaccination Contraception Avoid overcrowding Plant Fungicide Pesticide Burn ```

Answer 182

Crown gall - bacteria - many species - infection with bacteria from soil - tumour develops where bacterium has infected the plant. Often forms on roots and stems of plant. Spreads very quickly. Can interrupt flow of water and nutrients in plant=stunted plant growth. - kill bacteria in soil using heat. Kill plants infected. Barley Powderly mildew: - grass plants including barley - fungus produces spores to reproduce. Spores spread through wind - causes fluffy white growth on the leaves and plant stops being able to make chlorophyll. - fungicide Tobacco mosaic - tobacco, peppers, tomatoes - contact between plants or farmers hand - infects chloroplasts of plants leaves and changes their colour from green to yellow or white in a mosaic pattern. Stops them doing photosynthesis. - no treatment. Have to kill plant.

Answer 183

Salmonella Sexual renasmitred infections: HIV Gonnorhoea

Answer 184

Physical defences of plants Bark - Many plants are covered with a thick bark. This is an external layer of dead cells which forms a physical barrier against infection. In this way it is very much like human skin. Cell wall - Each plant cell has a cellulose cell wall which acts as another barrier against infection. Leaf cuticle - Leaves are covered with a waxy cuticle which also stops their cells from becoming infected. It is a strong barrier that pathogens find it hard to pass through. This means pathogens cannot get into the tissue underneath the leaf's waxy cuticle.

Answer 185

Chemical defences Some plants such as mint and witch hazel produce antimicrobial substances. These limit the spread of bacteria that were not stopped by physical defences. We now use these chemical defences in antiseptics for humans. Other plants, like stinging nettles, have developed poisons to stop themselves being eaten by herbivores. These do not defend plants from infection by pathogens. Other defences Farmers can now genetically engineer crop plants to be resistant to infections. Could be chemicals or physicals

Answer 186

Observation Many plant diseases can be identified simply by looking at the plant. - stunted growth - spots on leaves - decay - malformation - discolouration - presence of pests - growths Some traits showing that plant is infected Identification Farmers and gardeners often use books and the internet to identify plant diseases. They can also take a small cutting of an infected plant (or a photograph of it) to a local garden centre, which have staff that can often help identify and treat the disease. Laboratory tests Observation alone is not always enough to diagnose a plant disease. For diseases that are more difficult to identify, cuttings of the plant may be analysed by scientists in laboratories. Use of monoclonal antibodies Monoclonal antibodies can recognise a specific antigen. Samples of the plant tissue can be tested with the monoclonal antibody. If the pathogen's antigens are present in the plant tissue then the monoclonal antibody sticks to it. Another antibody is then added which can bind to the monoclonal antibody. This antibody has a marker on it, such as a dye, which then signals to the scientists that the monoclonal antibody recognised an antigen. Analysing DNA Another option is to analyse the DNA in the plant. Samples of the diseased plant can be analysed in the laboratory by scientists. Each plant pathogen has its own unique DNA. The plant can be tested for this DNA. If the pathogen's DNA is found in the plant tissue, this gives more evidence for that particular disease. This makes the disease easier to treat specifically, for example, using fungicides if it is found that a fungus has infected the plant. . . .

Answer 187

White blood cells Phagocytes Phagocytes are white blood cells that are attracted to pathogens and attach to them. Once they have attached to the pathogen, the phagocyte's cell membrane surrounds the pathogen and engulfs it. This means the pathogen is taken inside of the phagocyte. Enzymes found inside the phagocyte break down the pathogen and destroy it. Phagocytes do this to all pathogens that they encounter, so they are called 'non-specific'. Lymphocytes A scientific impression of a lymphocyte white blood cell Lymphocytes are another type of white blood cell. They recognise proteins on the surface of pathogens called antigens. Lymphocytes detect that these pathogen antigens are foreign and not naturally occurring within the body, leading the lymphocyte to produce antibodies. This process can take a few days, during which time a person may feel ill. The antibodies are released into the blood and bind to pathogens. This causes the pathogens to stick together, restricting their movement around the body and making it easier for phagocytes to engulf and then destroy them. Some pathogens produce toxins which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins. This means that the toxins cannot bind to body cells and cause damage. Both the antibodies and antitoxins are highly specific to the antigen or toxin that is made by the pathogen, therefore the lymphocytes that produce them are called 'specific'. Platelets White Blood Cells Adaptations - Irregular shape, they can change shape to squeeze out of blood vessels and get to the site of infection. Others have cytoplasm which can flow making it possible for the cell to change shape, surround and engulf bacteria. Can increase in numbers to fight disease. Platelets Platelets are cell fragments produced by giant cells in the bone marrow. Platelets stop bleeding in two main ways: they have proteins on their surface that enable them to stick to breaks in a blood vessel and clump together they secrete proteins that result in a series of chemical reactions that make blood clot, which plugs a wound.

Answer 188

Skin The skin covers almost all parts of the body to prevent infection from pathogens. If it is cut or grazed it immediately begins to heal itself, often by forming a scab, which prevents infection as the skin acts as a physical barrier. Parts of the body that do not have skin have developed other ways to prevent infection. For example, the eyes produce tears which contain enzymes. These enzymes are chemical barriers. Nose The nose has internal hairs, which act as a physical barrier to infection. Cells in the nose produce mucus. This traps pathogens before they can enter the lungs. When the nose is blown, mucus is removed and any pathogens are trapped within it. Trachea and bronchi A picture of a group cilia within the nose Ciliated cells The trachea runs from the nose towards the lungs. The cells that line the trachea also have hairs called cilia, which are much smaller than those in the nose. These are called ciliated cells. The ciliated cells waft their hairs in a motion like a Mexican wave at a football match and move mucus and pathogens upwards towards the throat where it is swallowed into the stomach. Other cells called goblet cells create the mucus in order to trap pathogens. The production of mucus in the airways is a physical barrier. Stomach Stomach acid does not break down food. It is part of the body’s non-specific first line of defence. Stomach acid is hydrochloric acid and, while it does us no harm, it is strong enough to kill any pathogens that have been caught in mucus in the airways or consumed in food or water. Stomach acid is a chemical barrier against infection. Phagocytes Phagocytes are white blood cells that are attracted to pathogens and attach to them. Once they have attached to the pathogen, the phagocyte's cell membrane surrounds the pathogen and engulfs it. This means the pathogen is taken inside of the phagocyte. Enzymes found inside the phagocyte break down the pathogen and destroy it. Phagocytes do this to all pathogens that they encounter, so they are called 'non-specific'.

Answer 189

The body's defence system against entry of any foreign body, including pathogens and agents such as pollen grains. The role of the immune system is to prevent disease. Phagocytes surround any pathogens in the blood and engulf them. They are attracted to pathogens and bind to them. The phagocytes membrane surrounds the pathogen and enzymes found inside the cell break down the pathogen in order to destroy it. As phagocytes do this to all pathogens that they encounter, they are called 'non-specific'. Lymphocytes are another type of white blood cell. They recognise proteins on the surface of pathogens called antigens. Lymphocytes detect that these are foreign not naturally occurring within your body and produce antibodies. This can take a few days, during which time you may feel ill. The antibodies cause pathogens to stick together and make it easier for phagocytes to engulf them. Some pathogens produce toxins which make you feel ill. Lymphocytes can also produce antitoxins to neutralise these toxins. Both the antibodies and antitoxins are highly specific to the antigen on the pathogen, thus the lymphocytes that produce them are called 'specific'. After the pathogen is removed some of the lymphocytes continue to remain in the immune system. These are called memory cells. If the same pathogen enters the immune system for a second time, the response is much more rapid.

Answer 190

Identical copies of an antibody produced by fusing a spleen cell with a cancerous white blood cell which can be designed to bind to many different substances. Antibodies are proteins produced by a type of white blood called lymphocytes. Pathogens have proteins on their surface called antigens. When a pathogen infects the body, the lymphocytes recognise these antigens as foreign and attack them by producing antibodies. Antibodies bind to specific antigens on pathogens. This means that only one type of antibody will bind to a matching antigen. Scientists discovered that we can make antibodies to bind to antigens on other substances, and not just those that are found on pathogens. Once bound, the antigens - and the substances they are found on - are merged tightly together. This makes them easier to identify and deal with. Formation of monoclonal antibodies An antigen is injected into a mouse. The mouse naturally produces lymphocytes, which produce antibodies specific to the antigen that was injected. Spleen cells, which produce the lymphocytes, are removed from the mouse. The spleen cells are fused with human cancerous white blood cells called myeloma cells to form hybridoma cells which divide indefinitely. These hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen.

Answer 191

Pregnancy test kits use monoclonal antibodies. These have been designed to bind with a hormone called hCG which is only found in the urine of pregnant women. Monoclonal antibodies are attached to the end of a pregnancy test stick onto which a woman urinates. If she is pregnant, hCG will be present in her urine and will bind to the monoclonal antibodies on the test stick. This will cause a change in colour or pattern which will indicate pregnancy. These specific monoclonal antibodies in the pregnancy test will only bind with hCG. Cancerous cells have antigens on their surface. Monoclonal antibodies can be designed to bind specifically with these antigens. As one monoclonal antibody will only recognise one specific antigen, different monoclonal antibodies have to be developed to recognise different forms of cancer. When injected into a person's bloodstream, the monoclonal antibodies travel around the body. They then bind to the antigens on the cancer cells. The antibodies may also carry markers that make it easy for doctors to see where they build up in the body. The marker may be a dye that will glow fluorescent under UV light. This makes it easier for doctors to identify a cancerous tumour, which can then be treated or removed. Monoclonal antibodies have been used successfully to detect and treat prostate cancer in men. Cancer treatment Monoclonal antibodies have also been designed to treat cancer by: Targeting drugs that have been attached to the monoclonal antibody directly to the tumour. The drugs could be radioactive or toxic substances. The advantages compared to using radiotherapy or chemotherapy are that only the cancer cells are targeted, leaving the healthy cells unaffected. This reduces side effects. Encouraging the white blood cells in your immune system to attack the cancer cells directly. Monoclonal antibodies are also used in a similar way to identify and diagnose infections, such as HIV, herpes and chlamydia.

Answer 192

Pathogens are microbes that cause diseases. Vaccines allow a dead or altered form of the disease-causing pathogen to be introduced into the body without causing the disease. The pathogens that are introduced contain a specific antigen. The antigen causes the body's immune system, specifically the lymphocytes, to produce complementary antibodies, which target and attach to the antigen. How vaccination works Altered form of a pathogen which cannot cause disease is injected into someone. Causes lymphocytes to make and then release complementary antibodies to the specific antigen that was injected. The antibodies attach to and clump the antigens together. Phagocytes engulf the antigens to remove them from the body. Some of the lymphocytes remain in the bloodstream as memory cells which can produce the specific antibody for the antigen. If the body is infected by the real pathogen, the memory cells release antibodies to fight off the pathogen and quickly destroy it.

Answer 193

Primary and secondary immune responses During a primary infection levels of antibodies slowly increase, peak at around ten days and then gradually decrease. This is what happens when someone is vaccinated with a dead or inactive pathogen or when someone catches a disease for the very first time. It is called the primary immune Following a vaccination, a person can become immune to the specific disease. This immunity gives protection against illness in an individual. The majority of the population must be vaccinated against serious diseases, which can reduce the chance of people coming into contact with specific pathogens, leading to herd immunity. response. A second exposure to the antigen that was in the vaccine, or to the same pathogen that made the person ill before, causes the white blood cells to respond much more quickly this time. This is the secondary immune response. The antibodies are produced so quickly by the memory cells that the pathogen is killed off before it can make the person ill. This is called being immune to a disease or having immunity.

Answer 194

Antiseptics Chemicals that kill microorganisms outside the body are known as antiseptics. Antiseptics can be used to clean an open wound as well as surfaces on objects such as toilets. Antiseptics therefore help to prevent the spread of disease. Antibiotics Antibiotics are medicines that interfere with the growth of bacterial cells. This means that the bacteria die as they cannot reproduce. Antibiotics can therefore be used to treat bacterial infections such as Salmonella food poisoning and tuberculosis. Antibiotics will only kill bacterial cells. This means that these medicines will not work against fungi or viruses. Antivirals It is difficult to develop drugs that can kill viruses. This is because the virus infects a cell and hijacks the cell's machinery in order to create more copies of itself. Destroying the virus will often mean destroying the cell that the virus is inside of. Antivirals are drugs that stop viruses from replicating. They can be used to treat viral infections. Antivirals are specific to one type of virus. E disinfectants E fungal E for protists

Answer 195

Name given to the laboratory procedures carried out to prevent the contamination of pure cultures of microorganisms. Preparation of the work area Clear the work space of all non-essential items. Clean the desk with disinfectant. Reason - this kills all unwanted bacteria and so decreases the chance of the agar plate becoming contaminated. Preparing the agar plates for growth of a colony of bacteria Glass petri dishes and agar gel must be sterilised before use by using an autoclave, or pre-sterilised plastic petri dishes can be bought. Reason - this will kill any unwanted bacteria that are present in the solution or on the petri dishes. Pour the agar into the sterile petri dishes and allow to set fully. Reason – this provides the selected bacterium with all the nutrients needed for them to grow. Plating the bacteria The following should be done beside a blue Bunsen flame. Reason - to create an updraft to stop the agar media getting contaminated with unwanted bacteria from the air. Swirl (do not shake) the bacterial suspension to make sure that the bacterial culture is well mixed. Reason - to make sure that the bacteria aren't all at the bottom of the container Sterilise the inoculating loop, by heating it in the Bunsen burner flame. Leave it to cool. Alternatively, sterilise it by placing it in pure alcohol for a few seconds. Reason - kills any unwanted bacteria that are present on the loop. Remove the lid from the bacterial bottle and put the mouth of the bottle in the Bunsen flame. Reason - to kill off any unwanted bacteria that could be on the bacterial bottle. Dip the inoculation loop into the microorganism solution and make streaks on the surface of the agar plate. Reason - this allows the bacteria to spread out and to grow in individual colonies on the agar plate. A lawn of bacteria can be produced by using a sterile spreader to evenly spread the bacteria across the whole of the plate. Replace the lid of the petri dish as soon as possible and secure with tape. Allow the plate to dry then label the half of the petri dish containing the media (do not label the top). Invert the plate and store it upside down. Reason - The lid stops additional unwanted bacteria in the air contaminating the plate. Do not fully seal the lid, as this will stop oxygen reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow. Labels are important, as this identifies the growing bacterium. If the lid is separated from the petri dish for some reason, the label will stay with the part that has the bacteria on it, so it can be identified. Incubate at a maximum temperature of 25°C in schools and colleges. Reason - this reduces the chance of growing harmful pathogens, which would grow at 37°C in a human body. Hospital laboratories would incubate plates at 37°C (body temperature) to allow quick growth and identification. Clearing up following the activity All contaminated materials need to be disposed of either in autoclave bags (for disposable materials that need to be sterilised, eg spreaders/Petri dishes) or pots (for items that are to be washed, sterilised and then reused). It is essential that all work surfaces need to be thoroughly disinfected at the end of the activity. Ensure that hands are washed with soap and water at the end of the activity.

Answer 196

New drugs are being developed all the time. Historically drugs have come from nature, as parts of plants and microorganisms have been extracted. One of the most famous discoveries was made by Sir Alexander Fleming, who discovered the antibiotic penicillin from the Penicillium mould. This antibiotic is still very important in the fight against disease. Plant extracts Certain drugs can be extracted from natural sources, and have been known about for a long time. For example, willow bark was used by the ancient Greeks to help cure fevers and pains. It was later discovered that the active ingredient was salicylic acid. This was modified by chemists into the substance we call aspirin, which is less irritating to the stomach than salicylic acid. Another example is the heart drug, digitalis, which is extracted from foxgloves. As many plant species might still contain drugs that are yet to be discovered, it is important that plants are protected. Once discovered, most plant drugs can be created in a laboratory by scientists at pharmaceutical companies. These companies now have synthetic versions of the plant extracts, and use these as the starting point to develop new drugs.

Answer 197

New drugs need to be tested and trialled before doctors prescribe them and patients take them. This allows drugs to be checked for: safety effectiveness dosage SafetySome drugs are toxic, and have other side effects that might be harmful to people Effectiveness/efficacy Checks how well the drug cures the disease, or improves symptoms DosageThis varies, and has to be closely controlled, as too high a concentration might be toxic

Answer 198

Preclinical drug trials The drugs are tested using computer models and human cells grown in the laboratory. This allows the effectiveness to be tested and if the drug is safe to use on living cells. Many substances fail this test because they damage cells or do not seem to work. Animal testing Drugs that pass the first stage are tested on animals. In the UK, new medicines have to undergo these tests. But it is illegal to test cosmetics and tobacco products on animals. A typical test involves giving a known amount of the substance to the animals, then monitoring them carefully for any side-effects. Human clinical trials Drugs that have passed animal tests are used in clinical trials. They are tested on healthy volunteers to check that they are safe. The substances are then tested on people with the illness to ensure that they are safe and that they work. Low doses of the drug are used initially, and if this is safe the dosage increases until the optimum dosage is identified.

Answer 199

Placebos, inactive versions of the drug, are used. Volunteers are split into groups, some receive the drug and others receive the placebo. It is important they do not know which they are taking. This is called a blind trial. Sometimes, a double-blind trial is carried out where the doctor giving the patient the drug is also unaware. Results from the groups are compared to ensure that the drug is having an effect and that any changes are not due the experimental trial process.

Answer 200

E viruses occupying cells can stimulate cancers E mental health E allergies E suppresses immune system

Answer 201

Statins- Statins are drugs that help to lower cholesterol in the blood. They do this by lowering its production in the liver. Stents- Coronary arteries that are blocked or have become narrow can be stretched open and a stent inserted to restore and maintain blood flow. Coronary artery bypass surgery-This involves taking a blood vessel from another part of the body, usually the chest, leg or arm, and attaching it to the coronary artery above and below the narrowing or blockage. This new section of blood vessel is called a graft. Heart transplants- A heart transplant is required in cases of heart failure.. donor heart is transplanted Artificial heart-Artificial hearts are plastic devices used occasionally to keep patients alive whilst waiting for a heart transplant. They can also be used to allow a patient's heart to rest to help it recover.

Answer 202

Obesity leads to high blood pressure and the build-up of fatty deposits in the arteries, which lead to cardiovascular disease. It also increases the likelihood of developing diabetes, another risk factor cardiovascular disease. Being obese - with deposits of lipids in the abdomen - increases blood pressure beyond normal levels and increases levels of blood lipids. Body fat also affects the body's ability to use insulin. Type 2 diabetes is where the body's cells lose their sensitivity to insulin - they no longer respond, or respond less effectively, to the insulin that's produced. Obesity accounts for 80 to 85% of the risk of type 2 diabetes. Rising obesity is linked with 'western diet' - a diet that includes energy-rich 'fast foods' and an inactive lifestyle. The risk of developing cardiovascular disease and type 2 diabetes can be reduced by eating a balanced diet, with unrefined, unprocessed, 'whole foods', and taking regular exercise. Drinking excess alcohol can damage the liver, the organ responsible for processing and breaking down alcohol. Smoking increases the risk of cardiovascular disease in several ways: W financial cost for the NHS

Answer 203

cancer is the result of changes in cells that lead to uncontrolled growth and division When a person is growing or replacing old and damaged cells, new cells are produced by mitosis. Sometimes, cells begin to divide uncontrollably. New cells are produced – even if the body does not need them. This produces a growth called a tumour.

Answer 204

-treating patients with currently untreatable conditions -growing organs for transplants and research. -generate healthy cells, replace old diseased cells and tissue -increase understanding of how diseases occur and develop by experimenting and observing with organs/tissues made from stem cells -test new drugs on stem cells ———————————————————- -not guaranteed success -finding stem cell donors. -obtaining and storing embryonic stem cells- collected before birth -Mutations in stem cells cultured, some behave like cancer cells. -Cultured stem cells contaminated with virus, transferred to a patient. - to collect stem cell, kills embryo. Unethical and religious beliefs that life starts at embryo. -view as commodity, not a human -research carried out by commercial clinics, reported successes are not subject to peer review. -exploit with expensive treatments - false hope of a cure -only in developmental stage

Answer 205

-Inserted gene could inactivate important gene in patient’s genome>disrupts cell cycle>tumour - immune system attacks gene tech vector. Inflammation or organ failure -vector virus targets wrong cells. Damages healthy cell/ lead to cancer/illness -modified virus could recover their original ability to cause disease when introduced to body and cause infection ———————————————————- -Potential to eliminate and prevent hereditary disease e.g cystic fibrosis by switching off disease-causing gene and fixing mutated gene -treat range of disease e.g cancer and heart disease by replacing mutated genes -making diseased cells more evident to immune system. Improve body’s ability to fight disease

Answer 206

- more medicines, diagnosis, treatment ways - target disease with specific medicine - gene therapy to treat disease - faulty aloes repair - replacement with normal alleys - predict patient’s response to drug treatment for effectiveness - reduce use of ineffective drugs, saves limited NHS resources - certain effective different drugs can be prescribed to different patients with the same disease that was caused by different factors - identify faulty alleles and predict chance of them developing a disease and their offsprings inheriting it - sequencing DNA in cancer cells. Can be compared to human genome sequence to work out which genes mutated, gives them ideas for developing medicines - produce specific monoclonal antibodies targeting cancer cells that had the identified gene mutation

Answer 207

Eyepiece graticule | Stage micrometer to calibrate the eyepiece graticule.

Answer 208

All the chemical reactions that happen inside a organism’s body Building up molecules Break down of molecules

Answer 209

Length of phase = (number of cells at that state/ total number of cells) x total length of time in cell cycle

Answer 210

High temperature- hyperthermia fever, heat stroke, tiredness, weak, lower blood pressure, headaches, muscle cramps, heavy sweating, intense thirst, low volume dark coloured urine Low temperature - hypothermia Shivering, tiredness, pale skin, low energy Dehydration- thirsty, dry mouth, tired, dark coloured urine Excess water intake: Headaches, personality and behavioural changes, irritation and drowsiness, nausea and vomiting High salt intake: Thirst, confusion, muscle twitch, bleeding in brain

Answer 211

In process of respiration Make glycogen Lipids Proteins

Answer 212

yes and no

Answer 213

use your knowledge

Answer 214

say what u think will happen based on what u know

Answer 215

say how something happens,+ 'because'

Answer 216

give an account of something or link facts/info/events of processes in a logical order

Answer 217

work out + include units

Answer 218

give similarities and differences between several things

Answer 219

look at the information in the question and bring it together to make a decision and come to a conclusion with evidence from the question

Answer 220

show information or name something on a graph, diagram or table

Answer 221

plan a method or experiment using ur knowledge

Answer 222

prove the statement in the question is right

Answer 223

add values to a table or diagram

Answer 224

recall one or more pieces of info

Answer 225

give evidence to support and answer

Answer 226

polymer - made from the 4 nucleotides (monomers) Thymine, Adenine, Guanine, Cytosine 2 strands of complementary base paired nucleotides twisting around each other forming a double helix held together by weak hydrogen bonds between A-T and G-C pairs. Phosphate backbone and deoxyribose sugar attached to a base

Answer 227

Transcription : DNA in nucleus and cannot leave. Dna unzips. Complementary to DNA’s template strand, mRNA is formed. mRNA leaves nucleus to ribosomes in cytoplasm Translation: tRNA has anticodons complementary to mRNA’s codons. tRNA carries a amino acid. mRNA’s sequence of bases corresponds to the order of amino acids. tRNa attaches to mRNA. Forms a amino acid chain. Chain folds and forms a unique 3D structure protein

Answer 228

Each amino acid is coded by a codon (3 bases). mRNA’s sequence of bases corresponds to the specific order of amino acids. tRNA ( which carries the amino acid) attaches to the mRNA in a specific order, as its anticodons are complementary to the mRNA. Different sequence of amino acids produces different proteins. mRNA is made from copying the base sequence of DNA therefore proteins depend on the DNA.

Answer 229

Catalase breaks down hydrogen peroxide. Cut potato cylinders using cork borer n drop into conical flask w/ hydrogen peroxide. Record volume of oxygen released using gas syringe. rate of reaction= volume of oxygen/time taken. Repeat w/ different concentrations of hydrogen peroxide. Solution of sodium carbonate and milk (alkaline cuz of the sdc) Phenolphalein indcitator added. pink. Add lipase, it breaks down the lipids in the milk producing fatty acids which lowers the pH of solution into acidic, colourless. 1/time Different temperatures affect rate of reaction Amylase breaks down starch. Test tubes containing different pHs. Place mixture of amylase and starch in. Remove a sample, test for presence of starch w iodine solution- blue/black colour when starch is present. When all starch is broken - amylase, iodine will not turn and remain orange-brown as starch is not present anymore, record disappearance of starch time. 1/time.

Answer 230

Iodine test for starch - grind sample. add iodine solution to sample, turns from orange/brown to blue/black in presence of starch Benedict’s test for reducing sugars: add benedicts solution -- blue to green/yellow/orange/brick red (conc) when heated with a reducing sugar. *sucrose is a non-reducing sugar and does not react with it* Emulsion test for lipids: add ethanol and then water. Cloudy white emulsion forms between lipid and water or rub brown paper on lipid, paper goes see-through Biuret test for proteins- Add Biuret reactant to solution. Turns from blue to mauve/purple

Answer 231

Enzymes have an specific-shaped active site Where specific substrates collide with and bind Forming a enzyme-substrate complex Lock and key theory Extreme heat or pH can denature enzymes by changing the shape of the site and preventing substrate binding Chemical reaction takes place and Enzyme-product complex is formed and products are released

Answer 232

convert energy from sun into glucose during photosynthesis producing biomass - feeds rest of food chain

Answer 233

Chlorophyll absorbs light energy. CO2 enters plant by diffusion. Water enters plant through osmosis in the roots. Light energy is used to split water, releasing oxygen gas and hydrogen ions Enzymes combine carbon dioxide gas with the hydrogen to make glucose Location of photosynthesis: chloroplasts As it contains chlorophyll which absorbs the light energy

Answer 234

requires light energy for reaction to split up water into hydrogen and oxygen, light energy is absorbed by chlorophyll. It takes in (light) energy

Answer 235

Effect of light intensity on photosynthesis in water plants: - capillary tube is attached to syringe + contains water that leads into test tube - lamp , changing distance - oxygen bubbles produced as it photosynthesis, forms gas tube in capillary tube. Use gas syringe to measure/oxygen concentration in water w data logger+ oxygen sensor - more bubbles produced w closer distance as + photosynthesis at higher light intensities Effect of different wavelengths of light on photosynthesis - different wavelengths, coloured acetate filters - effects of blue, green and red of the spectrum on photosynthesis - chlorophyll absorbs light energy - reflects green light, absorbs blue and red light. (Before using iodine, place lead in boiling water (kill n preserve) then again w boiling tube n ethanol (removes chlorophyll) Effect of chlorophyll on photosynthesis - presence or absence of chlorophyll effects - variegated plant(white and green) - test for photosynthesis (glucose produced->starch) using iodine solution, will turn black/green on the areas of the leaf with chlorophyll Effect of light exclusion on photosynthesis - cover part of the leaf and leave it for some time - cover it with iodine solution - areas exposed to light stain blue-black and the area that had light blocked remains orange-brown colour - as iodine turns blue/black in presence of starch

Answer 236

Temperature- optimum 37 oC Reaction rate increases w increase temp too high- bonds in enzyme structure break>change shape(denatures)>substrate no longer fits pH- too high/low, forces that hold the amino acid chains will be affected> denatures> substrate no longer fits Substrate concentration- Higher conc= higher rate initially Enzymes more likely to collide w substrate. After a while, no effect as active sites are all full Enzyme concentration Initial increase, stops increasing. Limiting factor is substrate.

Answer 237

plant needs light energy to break water into hydrogen and oxygen - increase CO2 is one of the reactants - increase Chemical reactions that combine CO2 and H2O are controlled by enzymes - increase, too high temp: decrease

Answer 238

If light intensity increases, rate increases but then will stop increasing as it’s not light intensity that is the limiting factor anymore, this applies to all of the factors

Answer 239

Diffusion- Gas and liquids. down concentration gradient. no energy required. (Particles move in both directions but net movement from high to low). Passive Examples- Liver: Diffusion of urea from liver cell (high urea concentration) to blood vessel (low concentration) Lungs: Diffusion of CO into alveoli (low concentration) from blood (high concentration ), diffusion of oxygen out of alveoli (high) into blood (low) Leaf: O2 diffuses out of cells (high concentration), CO2 diffuses into cell (as it has low concentration)

Answer 240

Movement from high to low water potential. Down concentration gradient. partially permeable membrane. Water molecules only. No energy required. Passive. WHEN concentration same on both sides, movement of water is same in both directions (no net movement) ``` Examples: Root hair cells take up water Water moves into plant cell, turgid, Water moves out of plant cell, plasmolysed/flaccid. Water moves into animal cell, bursts Water moves out of animal cell, shrivel ```

Answer 241

Particles go against concentration gradient. Low to high. Requires energy (ATP) Examples: Mineral ions from soil move to roots via active transport Glucose from small intestines move to blood via active transport

Answer 242

Interphase- Cellular growth (organelles double). DNA replicates and forms two copies of each chromosome, -dna unzips -forms two separate strands -bases on each strand exposed -free nucleotides line up against each of the strands (complementary pairing) -forms DNA base pairs -when strand complete, forms two identical molecules of dna Mitosis- (Prophase- nuclear envelope breaks down. Metaphase= chromosomes line up along equator. Anaphase- chromosomes move to opposite ends of the cells. Telephrase- new nuclear envelope reforms around each set of chromosomes - two nuclei ) Cytokinesis- cell membrane pinches inward, separates and enclose the two nuclei and split cell into two new identical daughter cells. Cytoplasm and cell membrane divided. - cell stops dividing temporarily -cycle repeats Length of phase = (number of cells at that state/ total number of cells) x total length of time in cell cycle

Answer 243

cells develop sub cellular structures, enable to fulfil specific functions+suited to its role in body to be efficient

Answer 244

Growth and development Replacing old/damaged cells. Asexual reproduction

Answer 245

embryos and adult animals and meristems in plants

Answer 246

Undifferentiated. can continuously undergo cell division. Provides new cells for growth, and to replace damage/dead specialised cells (specialised cells often lose ability to make new copies of themselves)

Answer 247

Embryonic- Only in embryos. Can differentiate into any cell type. Totipotent. Adult stem cells- Developed adult organisms. Specific areas of the body( bone, marrow, brain, muscle, skin and heart for a human). Differentiate into a narrower range of cell types (limited). Pluripotent

Answer 248

composed of glands which secrets chemicals (hormones) that gets carried in the bloodstream When the hormone reaches a target cell/organ. They alter the activity of specific target organs Once a hormone is used, it’s destroyed by the liver They can control the body and the effects are slower than the nervous system but they last for longer Pituitary gland in the brain- master gland

Answer 249

Thyroxine: Stimulates basal metabolic rate Controls speed oxygen/food products react to release energy Controls rate of which chemical reactions occur in the body at rest Metabolism=All the chemical reactions that happen inside a organism’s body Building up molecules Break down of molecules Metabolic reactions Animal use glucose: respiration. Make glycogen. Lipids. Proteins

Answer 250

Adrenaline: Initiates fight or flee situation Increases heart rate and breathing rate Boosts delivery of oxygen and glucose to the brain and muscles Increases conversion of glycogen to glucose - so more energy released in muscles Diverts blood area from areas not needed for the fight or flee state (e.g digestive system) towards the muscles Increases flow of blood to muscles

Answer 251

Low thyroxine levels in blood stimulate hypothalamus to release TRH, stimulates the pituitary gland to release TSH Which stimulates the thyroid to release more thyroxine and blood levels return to normal When thyroxine levels rise, it inhibits release of TRH from hypothalamus which in turn inhibits the release of TSH from pituitary so normal levels are maintained ``` TRH= thyroid regulating hormone TSH= thyroid stimulating hormone ``` Low thyroxine levels> TRH (hypothalamus)>TSH(pituitary)>thyroxine (thyroid)>normal thyroxine levels>inhibits TRH-TSH>maintain normal

Answer 252

FSH (follicle stimulating hormone) -causes a egg to mature in the ovary LH (luteinising hormone)- causes ovulation (mature egg released from follicle) Oestrogen- causes repair of uterus lining, thickens Progesterone- maintains uterus lining Testosterone- stimulates testes to produce sperm

Answer 253

- pituitary gland=FSH - FSH stimulates egg cell to mature in ovary, stimulates ovaries=oestrogen - oestrogen causes uterus lining to repair itself+/thicken+stops FSH from being released so only 1 egg will mature, stimulates pituitary gland to release LH - When FSH falls, oestrogen eventually falls too - LH peaks at around day 14 due to oestrogen, and egg gets released from ovary (ovulation) - empty follicle left from release of egg (corpse luteum) releases progesterone - Progesterone maintains uterus lining for implantation of egg, inhibits LH so only 1 egg released per cycle - If egg not fertilised, levels of progesterone falls - The uterus lining breaks=menstruation - Low levels of oestrogen+progesterone=FSH not inhibited anymore and cycle starts again - If egg fertilised, progesterone production continues

Answer 254

Hormonal contraceptives- has oestrogen+progesterone inhibits FSH+LH so eggs cannot mature/release. Preventing pregnancy. Thickens mucus in cervix, keep sperm from reaching egg

Answer 255

Oral contraceptives: side effects: changes in weight/mood/blood pressure (high levels of oestrogen), reduce risk of certain cancers Contraceptive injections/implants: Skin patches, (Contains slow release progesterone to inhibit maturation +release of eggs)

Answer 256

Physical barrier(condoms and diaphragms)- prevent sperm from reaching egg. Condoms: easy quick to use, tear or rip. Diaphragms- need to be put in before sex and left in for several hours afterwards Intrauterine devices (IUD coil): prevent implantation of embryo/release of hormone. risk of ectopic pregnancy (egg implants somewhere outside of uterus). can remain in position for up to 10 years. needs to be fitted by a health professional Spermicidal agents- kills/disables sperms. allergic reaction may happen. can be added alongside physical barriers (e,g condom) Abstaining from intercourse when egg in oviduct -if timings not accurate, chance of pregnancy high Surgical methods- male/female sterilisation (e.g vasectomy where sperm ducts are cut and tied). cannot be reversed. permanent method

Answer 257

Fertility drugs - FSH+LH to stimulate eggs to mature in the ovary. Some women difficulty in fertility= not enough FSH. Increase pregnancy chances. increases chance of multiple pregnancies -could lead to premature or underweight babies/death of mother In-vitro fertilisation treatment- involves giving a mother FSH and LH to stimulate maturation of eggs in ovary. eggs are collected from the mother and fertilised by sperm from the father in a dish in the laboratory. fertilised eggs develop into embryos. one or two embryos are inserted into the mother’s uterus. Allow people to have babies when there are body conditions that don’t allow them to. embryos can be screened for genetic diseases so only unaffected embryos are inserted into the womb. unused eggs can be used for research or donated to other couples. Side effects from the drugs used (severe headaches). possibility of multiple births. too many eggs develop. emotional and physically stressful. success rates are not high. ethical concerns (couple only want certain babies with desirable qualities). embryos not used may be destroyed (viewed as killing new lives)

Answer 258

act as messages from one part of plant to another. They control the rate of cell elongation, germination, flowering, development and ripening of the plant’s fruits, dropping of the fruit and shedding of leaves

Answer 259

Auxins: change the rate of cell elongation | high concentration of auxins: cells in shoots grow more, Cells in roots grow less

Answer 260

Gibberellins: ends seed dormancy (initiates seed germination). increase speed of germination. stimulate cell elongations (plants grow taller). promotes flowering. increase fruit size Ethene: speeds up fruit ripening in plants. controls cell division during plant growth

Answer 261

Auxins: selective weed killers (causes weed to grow too quickly and die). Auxins concentration higher on broader leaves and most weeds have broader leaves. rooting powder. Makes stem cuttings develop roots quickly. promoting growth in tissue culture. Stimulates cell division and elongation to grow whole plants from small sections of a parent plant Auxin or gibberellin: Growing seedless fruits. Spray the flower with hormones so fruit develops without the egg cells being fertilised in flowers therefore seeds don’t develop in the fruits. Parthenocarpic fruit development (development of fruit without fertilisation to produce a seedless fruit) Gibberellins: Breaking seed dormancy. So it can germinate at all times of the year

Answer 262

Homeostasis: maintenance of a constant internal environment in the body -human enzymes work best at 37oC (human body temperature) and they catalyse vital chemical reactions in the body Low temperatures can cause hypothermia and death High temp=dehydration, heat stroke, death Low temp=enzymes slower rate of reaction- less KE slower movement = less successful collisions High temp= enzymes to denature It maintains optimism conditions for enzyme action and all cell functions If conditions are outside of a specific optimum range, enzymes cannot function, it leads the organism to die

Answer 263

body temperature changes, brain sends nerve impulses to the skin skin has hairs, erector muscles, muscles, sweat glands hair erector muscles contract- raises skin hairs Hairs on skin trap air for insulation when standing up- to decrease heat loss. When lying flat there’s less air trapped, heat escapes- to increase heat loss tiny muscles in the skin can pull up by contracting or lay down the hairs by relaxing when it’s too hot or cold

Answer 264

Sweating and shivering Glands under the skin secrete sweat onto the surface- to increase heat loss by evaporation When liquids evaporate from surfaces they cool the surfaces Shivering- involuntary repeated rapid contraction and relaxation of muscles to quickly release energy from glucose in respiration so some of this energy is released as heat to warm up

Answer 265

Vasodilation: blood vessels that carry blood to the skin dilates. Blood flow in skin capillaries increases. Arterioles get wider. more heat is carried by the blood to the skin. More heat lost to the air by radiation. Vasoconstriction- blood vessels shrinks down. Arterioles narrow. Blood flow in skin capillaries decrease. Less heat carried by the blood to the skin. Reduces heat loss.

Answer 266

When blood glucose levels high, pancreas produces insulin. Causes more glucose to move from the blood into the cells. In liver cells, excess glucose converts into glycogen for storage in liver and muscles. Blood glucose levels decrease. When blood glucose levels low, pancreas does not produce insulin. Less glucose is absorbed into the cells So glucose is not converted into glycogen. And blood glucose levels don’t don’t decrease

Answer 267

When blood glucose levels high- insulin send signal to liver, muscles and other cells to store excess glucose in the form of glycogen When blood glucose level low- glucagon causes the liver to convert glycogen to glucose.

Answer 268

Type 1- Pancreas doesn’t produce enough insulin - immune system attacks pancreas, destroying the cells that produce insulin - uncontrolled high blood glucose levels - treatment by injecting insulin - can help control their blood glucose level by exercising (increases respiration in muscles therefore lowering blood glucose levels) and dieting (not eat foods that will largely increase blood sugar levels) Type 2-The body cells no longer respond to insulin produced by pancreas. high blood glucose levels. can be controlled by carbohydrate controlled diet and exercise regime. Carbohydrate is digested into glucose which can raise overall blood glucose levels. Exercise increases respiration in muscle therefore lowering blood glucose levels. insulin injections can be given in severe cases of type 2

Answer 269

Hypotonic- turgid/bursting Isotonic- flaccid Hypertonic- plasmolysed/shrivelled Haemolysis-bursting

Answer 270

Contains nephrons which remove excess Produces urine Kidneys control the loss of excess water, ions and urea to maintain water levels water, mineral ions and urea from the blood

Answer 271

Renal vein carries deoxygenated blood away from kidneys Renal artery carries oxygenated blood to the kidneys Glomerulus ( branched capillary network) in kidney filters blood that arrives through renal artery- removes water, glucose, salts and urea from blood. Proteins are too large to pass through so it remains in the blood. There is high pressure here to aid in the ultrafiltration. Filtered blood returns to circulatory system through renal vein after being filtered The waste substances pass from the capillaries into the glomerulus into the bowman’s capsules. Then the substances move from bowman’s capsule towards the loop of henle. Kidneys reabsorb molecules needed in the proximal convoluted tubule (all glucose + any water needed to maintain a balance of water level in blood plasma +any ions needed to maintain a balance of mineral ions in blood plasma). Waste substances that haven’t been selectively absorbed move from loop of Henle to distal convoluted tubule to the collecting duct as urine The urine passes through the ureter to the bladder where it is stored, then the urine is carried out of the body by the urethra

Answer 272

``` Renal artery Renal vein Medulla Renal pelvis Cortex Ureter ```

Answer 273

``` Renal artery and renal vein Glomerulus Bowman capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct ```

Answer 274

Causes kidney tubules to be more permeable so it reabsorbs more water

Answer 275

Osmoregulation Hypothalamus detects the changes of concentration of water in the blood plasma. If there is too little, the pituitary gland releases more ADH which causes the kidney tubules to be more permeable and selectively reabsorb more water so less water is lost in urine, Vice versa, if there is too much, the pituitary gland releases less ADH so less water is reabsorbed by the kidneys and more water is lost in urine. So blood water levels returns to normal Different temperatures: Hypothalamus monitors the temperature of the blood And imitates homeostatic responses when the temperature is too high or low When too low: shivering, vasconstriction, hair erector muscles contract, skin hairs raised When too high- sweating, vasodilation, hair erector muscles relax so hairs flatten

Answer 276

Nitrogen: Nitrogen gas in atmosphere converted to nitrates in soil by nitrogen-fixing bacteria. nitrates and ammonia absorbed by plants to make plant proteins. Plants eaten by animals and they make animal proteins, contains nitrogen. excretion and egestion- animal processes. Animal dies, decomposers break down corpse, urine(from excretion) and faeces(from egestion), results in nitrogen returning to soil as ammonia. Ammonia converts to nitrate by nitrifying bacteria. Denitrifying bacteria convert nitrates to nitrogen gas. Carbon- Carbon dioxide in atmosphere absorbed by producers for making glucose in photosynthesis. Animals eat plants, passing the carbon compounds. Animals eat animals passing carbon compounds along food chain. Animals and plants aerobic respire, releasing CO2. Animals and plants die. Decomposers break down the dead bodies, return carbon to atmosphere as CO2- decomposers aerobic respire which releases CO2. When decomposition is blocked, fossil fuels form. Combustion of fossil fuels release CO2 to atmosphere Water -evaporation. Energy from sun evaporates liquid water from all places (e.g ponds, lakes, land, oceans) to water vapour. Condensation- as water vapour rises, the atmosphere temperature cools and the water condenses from gas to tiny drops of liquid, forming clouds. Precipitation-water droplets in clouds get heavy and the water falls as rain/snow/hail/sleet surface run off- if a large volume falls/ground is already wet, some water runs along the surface of the ground to nearby water Percolation/Infiltration- when water absorbs into the ground, trickles deeper through gaps into the soil, and stored within underground rocks called aquifers Transpiration- plants allow some water it has to evaporate as vapour from leaves to continuously pull more water. Some water gets absorbed by plants through roots .

Answer 277

Nitrifying bacteria- converts nitrogen gas in atmosphere to nitrates in soil Denitrifying bacteria- converts nitrates back to nitrogen gas Nitrogen fixing bacteria- converts ammonia to nitrates Decomposers help return minerals and nutrients back to the environment so then the materials can be used by other organisms. When they break down dead plants and animals, the nitrogen is released back as ammonia in soil As bacteria and fungi decompose dead matter, they respire and release carbon back to environment as CO2

Answer 278

Carbon cycle- Carbon dioxide needed in Photosynthesis to make glucose for producers. Glucose important for chemical reactions in organisms. For production of DNA, skin, enzymes, nerves, fats, proteins and all organic compounds. Every living organism has carbon compounds. Nitrogen- used in plants to make proteins- plants need to grow. chlorophyll, amino acids, DNA Water cycle- Water is important for maintaining habitats, allowing nutrients to flow between organisms and environment, survival of organisms. Plants use water in photosynthesis to make glucose. Regulates body temperature in humans. Dissolving waste substances and carrying them out of the body in urine, faeces and sweat. For dissolving vital nutrients in bloodstream and delivering to cells

Answer 279

Temperature High temperatures denature enzymes, stopping enzyme activity and killing decomposers and therefore preventing decomposition. Decomposers need enzymes to break down the dead matter so they can absorb it. Low temperatures slow the rate of reaction of enzymes and prevents growth and reproduction of microorganisms, slows rate of decomposition. Oxygen availability- Oxygen needed for aerobic respiration by decomposer microorganisms, without oxygen microorganisms will die. Some bacteria can survive - bacteria that anaerobically respire. Slows or prevents decomposition Water content- Lack of water slows or prevents decomposition. Water needed for transport and to support reactions inside microorganisms. Decomposers need water to digest their food. Without water, microorganisms will die.

Answer 280

Individual organisms- any living thing or organism. A single member of a species. Species- individuals do not breed with individuals from other groups Populations- all members of a single species that live within a geographical area Communities- all the organisms that live within a habitat Ecosystem- living organisms (biotic) in particular area together interacting with non living components of environment (abiotic)

Answer 281

Abiotic factors Light intensity: Light needed by plants for photosynthesis. More light=increase rate in photosynthesis, increase plant growth rate. Different plants, different optimum light intensity. Temperature- affects rate of photosynthesis in plants and enzyme activity in organisms. Different organisms, different optimum temperatures Moisture levels- plants and animals require water to survive for important chemical reactions and transporting soluble substances. Waterlogged soils can kill plants as there is little oxygen so cells in roots unable to respire- although some plants grow best in high moisture levels e.g pitcher plants. PH of soil- different plants have different optimum pH levels. pH further from optimum level can decrease enzyme activity/reaction rate of enzymes or denature enzymes in organisms Wind intensity-wind speed affects transpiration rate. Transpiration affects photosynthesis as it ensures water and mineral ions are transported to the leaves (as water evaporates from leave surface, ensures more water can be continuously pulled to plant) Carbon dioxide levels- CO2 required for photosynthesis. Affects rate of photosynthesis Oxygen levels (for aquatic animals)- some aquatic animals can only survive in water with high oxygen concentrations

Answer 282

Availability of food- more food means organisms have higher chance of surviving/reproducing/population increase Presence of new predators- prey adapted to predators. If new predator introduced, cause imbalance in community-prey wouldn't be adapted to new predators, numbers decrease more rapidly as new predators advantageous. Competition between organisms- if two species compete for same resources, one better adapted, then that species will outcompete the other. continues until there are too few members of lesser adapted species New pathogens- if a new pathogen enters a community, the population living there will have no immunity or no resistance or it and the population decreases

Answer 283

Interdependence:all organisms in an community rely on each other for food, protection, shelter, etc for survival. Predator prey cycles. Cyclical change (when prey increases, predator increases and prey decreases, when prey decreases, predator decreases and prey increases). Any change in numbers of prey affects numbers of predators and vice versa. If one side were to be drastically affected, it greatly influences the other side (e,g introduction of new predators) Mutualism- organisms relying on other organisms of a different species for the benefits of both. E.g nitrogen fixing bacteria and leguminous plants. Parasitism. Parasitic organisms that live in/on a host organism, the parasitic organism benefits from it and the host suffers. E.g tapeworms Competition: keeps the balance of ecosystem by keeping populations in balance. Plays a role in evolution. Animals compete for food, water and territory. Plants compete for sunlight, water, mineral salts, space. Organisms compete for resources that they need to survive within a community. Interspecific competition occurs between individuals of different species. Intraspecific competition occurs between individuals of the same species.

Answer 284

First tropic level: producers- photosynthesis using light energy from sun to make glucose. Provides all the biomass for the food chain Second tropic level- primary consumer. herbivore or omnivore. Eats producers. Third tropic level- secondary consumer. Carnivore or omnivore. Eats primary consumer Might be additional consumers (e,g tertiary and quaternary). Final tropic level is called apex predator. Top of the food chain and has no predators

Answer 285

Biomass (amount of living material, tissue from living organisms, dry mass of a organism) is transferred along the food chain ``` The rest is used to complete life processes: Excretion Respiration Egestion Movement And so on ```

Answer 286

Biomass is steadily lost as it is transferred along the food chain Food chains are usually not long as biomass transferred decreases the longer the food chain as the total amount of biomass transferred becomes very small after a few tropic levels. Only *around* 10% of biomass is transferred from each tropic level to the next every time Percentage effiency transfer = (biomass in higher trophic level/ lower trophic level ) x100

Answer 287

Gamete: specialized sex cells that have half the number of chromosomes. Chromosome: organisation of DNA into tightly packed coiled strands. Gene-small section of dna that codes for a particular sequence of amino acids to make a specific protein allele/variant: different form/version of a gene Dominant: always expresses in phenotype itself when present, only one allele is needed Recessive: both copies of the recessive alleles need to be present to be expressed in the phenotype Homozygous: two identical alleles for the same characteristic Heterozygous: two different alleles for the same characteristic Genotype-collection of alleles that determine the characteristics of an organism (expressed as a phenotype) Phenotype-the visible characteristics of an organism

Answer 288

Genome: entire genetic material of an organism. The genome and its interaction with the environment influences the development of the phenotype of an organism e,g weight.

Answer 289

differences between individuals of the same species continious- shows a normal distribution at a peak (hill shaped). lots of different possible values for it discontinous- limied number of values genetic and envrionmental variation combine together to produce idfferent phentotyeos discontinuous variation is usally caused by one gene and is not affected by the environment continious variation, however, is often caused a mizture of your genes and your environment

Answer 290

All genetic variants arise from mutations Mutation is a random change in the gene or chromosome, arises spontaneous and happen continually Most have no effect on phenotype Some influence phenotype a very few fully determine phenotype

Answer 291

Mutations in coding DNA - Sequence of DNA could be changed. Changing DNA sequence can change the amino acids that make up the proteins. Enzymes are made of proteins and they have a specifically shaped active site If a mutation happens in the coding DNA that codes for the enzyme then the wrong amino acids could be used to make the enzyme which changes the shape of the enzyme’s active site and the enzyme will not work properly Mutations in non-coding DNA- Non coding parts of DNA can switch genes off and on. When genes are switched off, the process of transcription stops which means no mRNA is being made for that gene and therefore no protein can be made for that gene. So a mutation in non coding DNA may affect gene expression and whether the correct protein is synthesised or not

Answer 292

Sexual reproduction Advantages: -genetic variation -species can adapt to new environmental change -a disease is less likely to affect all individuals in a population Disadvantages: - time and energy needed to find a mate - both parents need to be fertile - not possible for a isolated individual to reproduce

Answer 293

``` Asexual reproduction Advantages: -population can increase rapidly if conditions are favourable -only one parent needed -more time and energy efficient -faster than sexual reproduction ``` Disadvantages: - no genetic variation, all offsprings genetically identical - disease may affect all individuals in a population - species may only be suited to one habitat - not adapted for change

Answer 294

Haploid: gamete that contains one set of chromosomes. Has half the total number of chromosomes that an organism needs to develop Diploid: cell that contains two sets of chromosomes, has total number of chromosomes needed to develop

Answer 295

Nuclei of gametes fuse to create a zygote The half chromosomes cross and when the gametes combine in fertilisation they create a embryo with the full set of chromosomes Meiosis role is so the end result, The embryo Has the full correct set of chromosomes after the two gametes combine with their half number chromosomes

Answer 296

The inheritance of traits controlled by a single gene with two alleles

Answer 297

Human body cells have 23 pairs of chromosome 22 pairs are autosomes, controls characteristics The last one pair carries genes that determine sex Males have X and Y sex chromosome Females have two X chromosomes 50% chance of female offspring, 50% chance of male offspring

Answer 298

Most phenotypic features are the result of multiple genes rather than single gene inheritance Some characteristics are controlled by a single gene however most characteristics are caused by the interaction of many genes

Answer 299

Before Mid 18th century Gregor Mendel Studied the inheritance of different characteristics In pea plants And flowers He discovered that: When he bred red flowered plants with white flowered plants, all the offsprings had red flowers If he bred these red flowering plants with each other, most of the offspring had red flowers, but some had white flowers. Mendel’s idea: The inheritance of each characteristic is determined by “units” that are passed onto descendants changed Mendel’s work expanded our knowledge of genetic inheritance before DNA had been discovered The idea that genes were located on chromosomes emerged in the late 19 century - better miscoopes and staining techniques allowed scientists to visualise the behaviour of chromosomes during cell division In early 20th, observation of chromosomes and Mendel’s units behaved in similar ways Led to theory that the units (now called genes) were located on chromosomes In mid 220, James Watson and Francis Crick worked out structure of DNA and modelled it using data from Rosalind Franklin Showed that bases occurred in pairs And the x ray data showed that there were two chains wounded in a double helix 21st century Entire human genome was sequenced Now scientists are working out the functions of our different genes And gene therapy is being developed

Answer 300

There is usually an extensive genetic variation within a population of a species

Answer 301

classification: animals divided into groups As more scientific equipment such as microscopes with higher magnification become available It allowed scientists to examine organisms in more detail and note important features Such as the identification of sex organs which allowed more divisions in the classification system to be created Helped to develop Linnaeus’ classification system -use of microscopes -studies of biochemistry -dna evidence Originally: artificial classification - purely on human obversvatiom to compare characteristics of different organisms Development of microscopes allowed cells to be examined in more detail and organelles within distinguished So more scientific approach to classification Natural classification: Phylogenetically (study of how related organisms are) helped to work out how species evolved from one another, molecular phylogenetic - comparing molecules inside organisms to see how similar they are. Developments in biochemistry- scientists can work out how similar organisms are on a molecular level E.f comparing structure of proteins used in aerobic respiration between organisms Comparing DNA sequences of different organisms - species that are more closely related likely to have fewer differences in the sequence of their dna bases Allowed classification to be developed , Theee domain system by Carl System based on evidence from analysing organisms on molecular level

Answer 302

Genetic variation in population due to mutations. Organisms better adapted to environment will survive and reproduce. So Advantageous alleles of variant organisms are passed on offspring. Over many generations, process of natural selection leads to evolution.

Answer 303

Evolution is a change in the inherited characteristics of a population over time through the process of natural selection which may result in the formation of new species

Answer 304

Fossil- preserved remains of dead organisms from millions of years ago - Hard body parts - e.g bones/shells. They don’t decay easily/they decay slowly so can be replaced by minerals as they decompose, leaving fossils - Parts of organisms that have not decayed due to the absence of conditions needed for decomposition. E.g dead animal trapped in ice - preserved traces of organisms. E.g footprints which become covered by layers of sediment and eventually becomes rock Fossil remains have been found in rocks of all ages Fossils of the simplest organisms - found in oldest rocks Complex organism fossils- in newest rocks Supports that simple life forms gradually evolved into complex ones

Answer 305

Bacteri can evolve quickly Cuz they reproduce fast Mutations in dna of bacteria can produce new characteristics Random mutation may cause some bacteria to become resistant to certain antibiotics- mutation protects bacterial cell from effects of antibiotic Antibiotics kill bacteria that are not resistant but anti biotic resistance ones survive and can reproduce with less competition from non resistant bacterial stains Genes for antibiotic resistance are passed on to offspring the anti resistant bacteria grow in population and overtime then whole population is antibiotic resistance because the antibiotic resistant bacteria were best suited to their environment Example of natural selection leading to evolution

Answer 306

Darwin: Studied variation in plants, animals and fossils During a 5 year voyage around the world On the ship HMS beagle Studies finches during his five week trip to the Galápagos Islands: concluded that a bird born with a beak more suited to the food available would survive longer than those who didnt Proposed that- Individual organisms within a particular species show a wide range of variation for a characteristic. Individuals with characteristics most suited to the environment are more likely to survive and breed successfully. The characteristics that have enabled these individuals to survive dare then passed onto the next generation. Theory of natural selection Wallace- Travelled the world. Studying warning colouration in animals/ Includes Golden Birdwing Butterfly/ Theory of speciation (formation of new and distinct species in the course of evolution due to separation and isolation). collected over 125,000 specimens. ' every species has come into existence conicident both in space and time with a closely allied species' sarawak's law.Made his own theory of evolution separate to Darwin wrote to darwin with his paper for peer review. Darwin and Wallace gathered and combined their research- joint writings 1858 And presented papers on their theories to the Linnaean Society Which didn’t receive much notice from other scientists. And following year, Darwin published On the Origin of Species book - presented his theory of evolution to other non-scientitsts which was hugely successful but controversial conflicting with the theoyr that god made all living things/

Answer 307

Incorporated into modern theory of biological evolution Used to study migratory and evolutionary history And past history of how organisms evolved

Answer 308

Quadrat (abundance) Transect (for distribution) Random sampling using a Place quadrat at random coordinates ``` Count the number of organisms in the Repeat steps Calculate total area of one Find total area of habitat being sampled Calculate mean number of organisms per quadrat by calculating the mean from the number of organisms counted from the quadrat divided by the number of Times the quadrat was placed down ``` Transect Quadrat placed at regular distances, e,g every five meters Along a line called transect To link changes in distribution due to abiotic factors such as light intensity

Answer 309

Land Pollution, air pollution, water pollution, noise pollution, increased waste, deforestation, peat hog destruction, global warming due to CO2 emissions. Land being cleared for human uses. Hedgerows being removed. Hunting. Destruction of habitats. Introducing predators and invasive species to other places. Conservation and species and habitats by charities, governments and individuals (conservation projects) Breeding programs for endangered species Protection and development of new endangered habitats Replanting hedgerows Reducing deforestation and release of greenhouse gases Recycling rather than dumping waste in landfills. Illegalising poaching and hedgerow removal. Seed banks. Areas protected from exploitation set. Afforestation, education. Selective logging. Monitoring using satellites to check no illegal activities are taking place (wide deforestation)

Answer 310

Land being cleared for human uses for building, quarrying, agriculture and waste disposal (landfill) Area of rainforest being cut down reduces biodiversity Land use for farming No shelter/food The hedges used to make boundaries of the fields can get in the way of machinery So farmers remove the hedgerows To allow for more easier harvest However hedgerows provide lots of biodiversity They provide food and shelter for a range of animals Birds rely on hedges for their nests and to raise offsprings safely hidden from predators Hedgehogs and mice also use it to nest, shelter and hibernate Without hedges these organisms suffer and numbers may decline which has a knock on effect on the rest of the ecosystem Deforestation: Humans have been deforesting woodlands to build houses, get wood materials and agriculture Deforestation destroys the habitats of organisms that live in it Therefore This kills individuals of many species No shelter/food Hunting of endangered species Poaching of organisms bringing organisms to close extinction Overhunting of organisms for food can reduce species numbers Pollution More fossils fuels being burnt for heat and power More food being grown Land taken over for industry and housing Air pollution- combustion of fossil fuels + others contributes to greenhouse effect and leads to global warming Melts polar ice caps and colder places - polar bears Also releases soulful dioxide and nitrogen oxides which causes acid rain Acid rain removes minerals and nutrients from soil that plants need Increase in pH with heavy acid rain downpours can kill or injure plants On fish and wildlife, organisms that are sensitive to pH. At pH 5, most fish eggs cannot hatch High pH may lead fishes to die Water pollution Fertilisers Eutrophication Algae bloom and decrease in oxygen levels Kills aquatic organisms s Pesticides Blown in streams and rivers Eaten by organisms Bioaccumlation up food chain Kills organism at top of food chain Due to the accumulation of the toxic pesticide Higher concentrated lethal dose Greenhouse effect Global warming Carbon dioxide, water vapour and methane Released from combustion Global warming, melting of polar ice caps, overall temperature increases which includes ocean temperatures New climate patterns, Habitat loss, Altered competitive relationships, Invasive species, Due to migration due to habitat loss, Disrupt the match between organisms and local environment, Reducing survival and reproduction

Answer 311

Conversation projects Benefits Maintains biodiversity- more species can survive. Food chains and interdependence, species rely on others for survival. Ecotourism- tourism contribution to preservation and provides funding for project Knowledge- some unknown species may become extinct before discovering them. Important to know their importance in the ecosystem and any unique traits of the organism that may help in other fields of research e.g medicine Medicines - conserving ecosystems means potential to uncover new drugs in plants that may allow us to treat more diseases Challenges: Conservation costs money, Must be able to raise enough money to carry out conservation Lack of understanding - eduction and outreach programmes needed to educate people on the importance of conserving, Monitoriarion of it: difficult to monitor the effect of any conservation scheme if it actually has positive effect, Changing laws and legislations p- takes time as legal documents have to pass through a lot of comities before they become the law and the situation could worsen during it.

Answer 312

Pollution indicators. Intricately species - presence, abundance or absence of these organisms provides information of the pollution in the environment Water- freshwater animals sensitive to oxygen levels- stonefly larvae, freshwater shrimps. No pollution adapted for surviving in polluted conditions. e.g blood worms, sludge worms. high level of water pollution. No pollution- mayfly larva and stonefly nymph. Some pollution- no mayfly larva/stonefly nymph but freshwater shrimp and fly larva still Moderate- bloodworm, Water louse, High- sludge worm, red tailed maggot. Very high- no living organisms Air: Bushy lichens - very clean air. Leafy lichens can survive small amount of air pollution. Crusty lichens-more polluted air

Answer 313

Ability/measure of human populations to access affordable food of sufficient quality and quantity. Increased human population, birth rates increasing, better access medical care, less death rate Changing diets, scare food resources are transported to be sold to other areas from areas which need them. Wealthier countries tending to eat more meat which is more energy intensive to produce than plant-based foods. New pests and pathogens- attacks crops and farm animals. And can evolve. Environmental changes - global warming, climate change. More droughts and less crop yield. This may be counteracted by increase yield due to higher carbon dioxide concentrations Prices of foods increasing and increased oil prices could affect the production and distribution of food. Increased costs of farming

Answer 314

Hydroponics: An extreme form of growing crops in glasshouses is called hydroponics. Soil is replaced by a mineral solution pumped around the plant roots.Removing the soil means there's no risk of soil organisms causing disease but the plants have to be supported.Monitoring and adjusting the concentrations of minerals in the solution enable the grower to control growth. Hydroponics allows crops to be grown in regions where there's little or no soil. Due to the costs involved, hydroponics is used only for high-value crops. Intensive farming- growing high yield crops, adding fertilisers, battery farming, herbicides and pesticides. Pesticides, insecticides, herbicides, fungicides- to get rid of pests which may decrease plant yield and rid of weeds and other plants which may provide competition over resources for desired crops. Fungicides to kill fungi diseases on plants that decrease crop yield. Insecticides to kill insects( which feed on/live on/damage plants and reduce their quality/causes plant to die.) Biological control-releasing a natural predator into the crop growing area, the number of pests can be reduced. Artificial environments- Some food products have been grown in artificial environments to increase productivity. Examples include growing tomatoes in glasshouses and salmon in fish farms. Selective breeding- humans breed plants and animals for particular genetic characteristics that increased yield or quality Genetic engineering- modifying the genome of an organism by introducing a gene from another organism to result in a desired characteristic for increased yield or quality Biotechnology - novel foods(recently introduced or produced using new process) E.g fermenters, produce fungus to collect+purify to produce proteins Fertilisers- increase plant growth and yield, and quality. Replenishes minerals taken from plants to soil for new plants.

Answer 315

quantity+quality. animals selected to cannot harm, reduced genetic variation- attack by new/specific pathogens destructive. rare disease genes unknowingly selected=genetic disorders with specific organisms. creation of physical problems in specific organism. Genes and their different alleles within a population=gene pool. Inbreeding>reduced gene pool, more difficult to produce new varieties in future which may be economically important. also makes organisms prone to certain diseases/inherited defects

Answer 316

genetic engineering is a process which involves modifying the genome of an organism to introduce desirable characteristics

Answer 317

selection of gene with desired characteristic. Restriction enzymes used to isolate required gene from chromosome- cut DNA at a specific sequence and leave sticky ends (short strands of unpaired DNA). gene inserted into vector -usually plasmid from bacterial cell. Plasmid is cut with same restriction enzymes, so gets corresponding sticky ends. gene and plasmid sticky ends joined together w DNA ligase enzyme .vector transferred back into bacteria host cells. host cells now have gene from another organism and so are said to be transgenic, vector transferred to organism/or replication of modified bacteria cell

Answer 318

faster and more efficient way of getting same results as selective breeding. Improve crop yield/quality, important in developing countries. reduce world hunger. Introduce herbicide resistance- results in less herbicides being used, weeds quickly and selectively killed. Insect/pest resistance inserted into plants- produces toxins, discourage insects from eating. Sterile insects created e.g mosquito>breed> infertile offspring> reduce spread of diseases: malaria/dengue fever/Zika virus. ——————————————————————————————— Transfer of selected gene into other species, what benefits may harm another. not ethical to interfere w nature. GM crop seeds often more expensive> people in developing countries cannot afford GM crops could be harmful, e.g toxins from crops detected in some people's blood. allergic reactions. Pollen produced by plants toxic and harm pollinators

Answer 319

Agricultural solutions: Selective breeding. Decide which characteristics are important enough to select-Choose parents that show these characteristics from a mixed population. They are bred together-Choose the best offspring with the desired characteristics to produce next generation-Repeat process continuously over many generations, until all offspring show the desired characteristics. Genetic modification:genes are transferred to animal cells during early development Intensive farming- series of techniques maximise yield of animal/plant crops: remove competing plants, Herbicide- allows more energy to be transferred to crop, reduces biodiversity, harmful effect on health. Pesticide spray- prevents energy being transferred from crop to consumers, reduce biodiversity, may poison helpful organisms. Keep animals indoors'Battery' farmingReduces energy transferred to environment so more energy available for growthIncreased risk of disease. Lower quality product. Ethical concerns. Producing maximum food product yield using minimum space by use of inorganic fertilisers and pesticides to aid plant growth and reduce loss. Maximising animal growth rates and minimising labour inputs by mechanisation. Biological control is an alternative to using pesticides. By releasing a natural predator into the crop growing area, the number of pests can be reduced. This can have unforeseen consequences as the numbers of different organisms in the food web are changed. There have been examples of the predator becoming a more serious pest than the original problem. Biotechnology- Development of novel foods could aid in meeting the food demand of the growing human population. A good example of this is the fungus Fusarium which is used to produce mycoprotein . The fungus is grown in large containers called fermenters. The conditions inside are maintained to promote maximum growth: the pH and temperature are maintained at the optimum level, the temperature is controlled by a water jacket that surrounds the whole fermenter, sterile oxygen is added to make sure that aerobic respiration occurs, a food source like glucose syrup is added, mixture inside is stirred to make sure all the oxygen and nutrients are equally distributed, Stainless steel with water jacket and paddles. Steam and nutrients enter at top. Cooling water and air at bottom. Exhaust at top right. Cooling water leaves near top. Outlet for the product at base.Diagram of a fermenter. After the fungus has fully grown in the fermenter, it is harvested and purified and the process is then repeated with a new batch of ingredients. Producing protein from fungus is much more efficient than producing meat from livestock. Only about 10% of the energy found in grass is transferred to animals like cows that eat it. 1000 g of plant carbohydrate can produce up to 14 g of beef, 49 g of chicken or 136 g of mycoprotein. Additionally, fermenters can be used to produce protein in places where grass and livestock cannot grow.

Answer 320

Health= state of physical, mental and social well-being - not just being free from disease. Factors work together to affect physical and mental health. Diseases stop part of the body from working properly.

Answer 321

communicable: can be transferred from organism to another.e.g measles,malaria non-communicable: not transferred between other organisms, eg cancer or Type 1 diabetes

Answer 322

HIV infections> AIDS, affects efficiency of immune system. Ppl w/ HIV and AIDS get more infectious diseases than healthy person. common: tuberculosis. Tuberculosis=bacterial infection affecting lungs. Viruses living in cells can be the trigger for cancers. Cervix cancer linked w/ virus present in female reproductive system HPV. reaction of immune system to pathogens/other foreign bodies=trigger allergic reactions=skin rashes, asthma. E.g severe respiratory infections in babies - asthma in later childhood. Severe physical ill health= depression/mental illness.

Answer 323

Animals, Direct contact, Body fluids transfer, Water, Air, Unhygienic food preparation, Vector, Plant, Wind Direct contact, Farmers, Herbivores and omnivores eating plants, Rain, Insects

Answer 324

Animals, Sterilising water, Antiseptics Sterilising surfaces- suitable hygiene personal Suitable hygiene in foods- cooking foods thoroughly and preparing them in hygienic conditions, Vaccination, Contraception, Avoid overcrowding,Plant, Fungicide, Pesticide, Burn

Answer 325

Crown gall: bacteria, many species e.g grapes, soil, tumour develops where bacterium has infected plant, forms on roots+stems of plant, spreads very quickly, can interrupt flow of water and nutrients in plant=stunted plant growth, kill bacteria in soil w heat. Kill plants infected. Barley Powderly mildew: grass plants including barley, fungus produces spores to reproduce. Spores spread through wind, fluffy white growth on leaves, plant stops being able to make chlorophyll,fungicide. Tobacco mosaic: tobacco, peppers, tomatoes, contact between plants/farmers hand, infects chloroplasts of plants leaves, changes colour from green to yellow/white in a mosaic pattern, stops photosynthesis, no treatment, have to kill plant.

Answer 326

Salmonella Sexual renasmitred infections: HIV Gonorrhoea Chlamydia

Answer 327

Bark - external layer of dead cells, forms physical barrier against infection. Cell wall - cellulose cell wall, acts as another barrier against infection. Leaf cuticle - Leaves covered w waxy cuticle, barrier pathogens find hard to pass through, cannot get into tissue underneath waxy cuticle.

Answer 328

- produce antimicrobial substances- limit of spread of bacteria not stopped by physical defences. e.g mint, witch hazel. - poisons to stop herbivores eating them- do not defend plants from infection by pathogens E.g stinging nettles - genetically engineer crop plants to be resistant to infections

Answer 329

- Observation: identified simply by looking at plant traits. stunted growth, spots on leaves, decay, malformation, discolouration, presence of pests, growths. - Gardening/farming books/internet to identify plant diseases. - small cutting/photo of an infected plant to local garden centre, staff help identify+treat the disease. - Monoclonal antibodies recognise a specific antigen. Sample tested w monoclonal antibody. If pathogen's antigens present, monoclonal antibody sticks to it. Another antibody (has marker on it e.g dye) then added- bind to monoclonal antibody. signals to scientists the monoclonal antibody recognised an antigen. - Analysing DNA. Samples analysed in laboratory by scientists. Each plant pathogen, own unique DNA. If pathogen's DNA is found in plant tissue= evidence. easier to treat specific, e.g using fungicides if found fungus infected plant.

Answer 330

Phagocytes- white blood cells, attracted to pathogens and attach to them. Once attached, phagocyte's cell membrane surrounds pathogen, engulfs it. pathogen taken inside of phagocyte. Enzymes found inside phagocyte break down pathogen and destroy it. Phagocytosis. Adapt: irregular size, squeeze out of blood vessels, get site of infection easier, cytoplasm which can flow can change shape and engulf, can increase in numbers to fight disease. Lymphocytes- recognise proteins on surface of pathogn (antigen) are foreign, not naturally occurring within body, produce antibodies. antibodies released into blood, bind to pathogens. causes pathogens to clump together, restricting their movement around body and making it easier for phagocytes to engulf+destroy. produce antitoxins to neutralise toxins (cannot bind to body cells+cause damage). specific Platelets- cell fragments produced by giant cells in the bone marrow. proteins on their surface that enable them to stick to breaks in a blood vessel and clump together. they secrete proteins that result in a series of chemical reactions that make blood clot, plugs wound. Blood clot dries and creates scab, physical barrier.

Answer 331

Skin- physical barrier. prevent infection from pathogens. immediately begins to heal if cut. Secretes sweat which has lysozymes that destroys pathogens. Nose- tiny cilia internal hairs, physical barrier to infection. Goblet cells in nose produce mucus. traps pathogens before can enter lungs. When nose blown, mucus is removed+any pathogens trapped. Trachea+bronchi- from nose>lungs. Ciliates cells that line the trachea have cilia hairs, smaller than those in the nose, waft their hairs in motion to move mucus+pathogens upwards towards throat where swallowed into stomach. goblet cells. Physical barrier - mucus in airway. Stomach acid does not break down food. Stomach acid HCl, strong enough to kill any pathogens caught in mucus in airways/consumed in food or water. chemical barrier. Phagocytes- white blood cells that are attracted to pathogens, attach to them. phagocyte's cell membrane surrounds the pathogen and engulfs it. pathogen taken inside of the phagocyte. Enzymes inside phagocyte break down pathogen, destroy it.

Answer 332

immune system = prevent disease. Phagocytes surround any pathogens in blood and engulf them. They are attracted to pathogens and bind to them. phagocytes membrane surrounds pathogen and enzymes inside cell break down pathogen in order to destroy it. do this to all pathogens they encounter, non-specific Lymphocytes= recognise proteins on surface of pathogens called antigens. Lymphocytes detect that these are foreign, produce antibodies. cause pathogens to stick together, make it easier for phagocytes to engulf them. also produce antitoxins to neutralise toxins. antibodies and antitoxins highly specific to the antigen on the pathogen. After pathogen removed, some lymphocytes remain in immune system. memory cells. If same pathogen enters immune system 2nd, response much more rapid.

Answer 333

Identical copies of antibody. Antibodies- proteins produced by lymphocytes. proteins on pathogen surface- antigens. When pathogen infects body, lymphocytes recognise these antigens as foreign and attack them by producing antibodies. Antibodies bind to specific antigens on pathogens (only one type of antibody will bind to a matching antigen). antibodies can bind to antigens on other substances, not just pathogens. Once bound, antigens - and substance they are found on - are merged /clumped tightly together, easier to identify/deal with. Formation of monoclonal antibodies: antigen is injected into a mouse. mouse naturally produces lymphocytes, which produce antibodies specific to the antigen that was injected. Spleen cells, which produce the lymphocytes, are removed from the mouse. The spleen cells are fused with tumour myeloma cells to form hybridoma cells which divide indefinitely. These hybridoma cells divide, produce lots monoclonal antibodies specific to original antigen.

Answer 334

Pregnancy test kits= monoclonal antibodies. designed to bind w hormone called hCG- found in urine of pregnant women. hCG bind to monoclonal antibodies on test stick. cause change in colour/pattern, indicate pregnancy. specific, only bind with hCG. Design: bind specifically with specific form of cancer’s cells antigens. Injected into bloodstream, monoclonal antibodies travel around body. bind to antigens on the cancer cells. carry markers- easy for doctors see where build up. marker= dye that glow fluorescent under UV light. easier for doctors to identify cancerous tumour, treated/removed. E.g detect herpes/treat prostate cancer in men. treat cancer by: targeted drugs attached to monoclonal antibody directly to tumour. radioactive or toxic substances, only cancer cells targeted, leaving healthy cells unaffected, reduces side effects/Encouraging wb cells in immune system to attack cancer cells directly.

Answer 335

Altered form/dead of pathogen- cannot cause disease. lymphocytes make+release complementary antibodies to specific antigen injected. antibodies attach to+clump antigens together. Phagocytes engulf antigens, remove them from body. Some of lymphocytes remain in bloodstream-memory cells that produce specific antibody for antigen. If body infected by real pathogen, memory cells release antibodies to fight off pathogen and quickly destroy it.

Answer 336

primary=antibodies slowly increase, peak around ten days, gradually decrease. When vaccinated wi dead/inactive pathogen//catches a disease for first time. After, immune to specific disease, protection against illness in individual. majority of population must be vaccinated/immune, reduce chance of ppl into contact w specific pathogens/protects vulnerable= herd immunity second exposure= antigen in vaccine/same pathogen, white blood cells respond much more quickly. antibodies produced so quickly by memory cells, pathogen killed off before make ill == immunity.

Answer 337

Antiseptics: Chemicals, destroys microorganisms outside body. clean an open wound+surfaces on objects. Help prevent spread of disease. Antibiotics- medicines interfere w growth of bacterial cells - bacteria die, cannot reproduce. treat bacterial infections(Salmonella food poisoning and tuberculosis) only kill bacterial cells. Antivirals- difficult to develop drugs kill viruses. virus infects a cell, hijack cell in order to create more copies of itself. Destroying virus=destroying cell virus inside of. Antiviral drugs stop viruses replicating. treat viral infections but specific to 1 type of virus. disinfectants- antiseptics but only for surfaces as it damages tissues Fungicide- kill/prevent growth of fungi+their spores

Answer 338

Aseptic - laboratory procedures carried out to prevent contamination of pure cultures of microorganisms. Clear work space of non-essential items, Clean w disinfectant (kills, decreases chance agar plate contaminated). Glass petri dishes, agar gel sterilised before use using autoclave/pre-sterilised plastic petri dishes. Pour agar into sterile petri dishes, allow to set fully- provides selected bacterium w all growth nutrients. Plating bacteria beside blue Bunsen flame. creates updraft to stop contaminated w unwanted bacteria from air. Swirl (do not shake) bacterial suspension, bacterial culture well mixed- makes sure bacteria aren't all bottom of container. Sterilise inoculating loop heating in Bunsen burner flame/ place in pure alcohol for few secs- kills any on loop. Remove lid from bacterial bottle, put mouth of bottle in Bunsen flame. kill unwanted bacteria on bacterial bottle. Dip inoculation loop into microorganism solution, make streaks on surface of agar plate. allows bacteria spread out, grow in individual colonies on agar plate. lawn of bacteria produced using sterile spreader, evenly spread bacteria across whole of plate. Replace lid of petri dish, secure w tape. Allow plate to dry, label part or petri dish containing media (do not label top). Invert plate, store upside down.lid stops additional unwanted bacteria in air contaminating plate. Don’t fully seal lid- stops oxygen reaching bacterium, may encourage harmful anaerobic bacteria grow. if lid separated from petri dish, label will stay w part bacteria, identify growing bacterium. Incubate, max temp 25°C in schools/ colleges. reduces chance of growing harmful pathogens( grow at 37°C) in a human body. Hospital laboratories- incubates plates 37°C (body temperature) to allow quick growth/identification. All contaminated materials disposed in autoclave bags (disposable materials sterilised, eg spreaders/Petri dishes)/ pots (washed, sterilised, reused). work surfaces thoroughly disinfected. hands washed w soap+water.

Answer 339

New drugs being developed all time. parts of plants/ microorganisms extracts. E.g Sir Alexander Fleming- antibiotic penicillin from Penicillium mould. Anti microbial properties of chemicals of mint/witch hazel extracted - natural sources, willow bark: ancient Greeks, help cure fevers/pains. later discovered active ingredient salicylic acid> modified by chemists into aspirin (less irritating to stomach than salicylic acid). heart drug digitalis- extracted from foxgloves. many plant species might still contain drugs yet to be discovered, important plants should protected. Once discovered, most plant drugs created in laboratory by scientists at pharmaceutical companies. synthetic versions of plant extracts, uses these as starting point to develop new drugs.

Answer 340

New drugs need tested/trialled before doctors prescribe+patients take them. allows drugs to checked for: safety, effectiveness, dosage Safety- Some toxic/side effects harmful to people Effectiveness/efficacy- Checks how well drug cures disease/improves symptoms Dosage- varies, has to be closely controlled, too high a concentration= toxic

Answer 341

Preclinical drug trials - drugs tested using computer models, human cells grown in laboratory. allows effectiveness to be tested+ if drug is safe to use on living cells. Many substances fail this test, damage cells/not seem to work. Animal testing - Drugs that pass first stage tested on animals. new medicines undergo these tests. illegal to test cosmetics and tobacco products on animals tho. givin known amount of substance to animals, then monitoring them carefully for any side-effects. Human clinical trials- Drugs passed animal tests used in clinical trials. tested on healthy volunteers to check safe. substances then tested on people with illness to ensure they’re safe/work. Low safe doses used initially, dosage increases until optimum dosage identified.

Answer 342

inactive versions of drug used. Volunteers split into groups. some receive drug, others receive placebo Blind trial= patients don’t know which they taking, doctors do double-blind trial= doctor giving the patient drug is also unaware. Results from the groups compared to ensure drug has effect purely and not from patient’s belief + reliable results + no bias Open-label trial - both patient and doctor knows about treatment - used when there is no other treatment/ patient is so ill doctor believes unlikely to recover from illness

Answer 343

- viruses occupying cells can stimulate cancers - mental health - triggered immune system of foreign/pathogens > allergies - defects in immune system (more likely infected)

Answer 344

Statins- drugs, lower blood cholesterol by lowering production in liver. Stents- Coronary arteries that are blocked/narrow can be stretched open, stent inserted to restore and maintain blood flow (catheter inserted, balloon inflated, pushes fatty deposits against the walls, catheter removed) stroke, bleeding, heart attack Anti platelets- reduce stickiness of blood platelets to reduce heart attack risk Beta blockers- lower blood pressure by blocking effects of adrenaline Nitrates- widens blood vessels, relaxes walls. Mechanical valves - lasts longer but prone to blood clotting - need long term anti-clotting medication. Restores proper blood flow. Biological valves- from human donor/animal tissue. More likely to wear out, less risk of blood clots. Restore proper blood flow. Coronary artery bypass surgery- taking a blood vessel from another part of body, usually chest/leg/arm, attaching it to coronary artery above+ below narrowing or blockage. new section of blood vessel= graft. Heart transplants- required in cases of heart failure. donor heart transplanted. Need to take immunosuppressants. Risk of rejection. Expensive operation and aftercare. Life-saving, improves quality of life. Few donor hearts available. Artificial heart- plastic devices used occasionally to keep patients alive whilst waiting for heart transplant. Also allow patient's heart to rest to help it recover. Blood clotting> stroke.

Answer 345

Obesity>high blood pressure+ build-up of fatty deposits in arteries>cardiovascular disease. Increase risk of developing diabetes, another risk factor of CVD Being obese - w deposits of lipids in abdomen - increases blood pressure beyond normal levels+ levels of blood lipids. Body fat affects body's ability to use insulin. Type 2 diabetes= body's cells lose their sensitivity to insulin - no longer respond/respond less effectively to the insulin produced. Obesity> 80-85% of risk of type 2 diabetes. Rising obesity linked with 'western diet' - diet includes energy-rich 'fast foods' + inactive lifestyle. risk of developing CVD and type 2 diabetes reduced by balanced diet( unrefined, unprocessed, 'whole foods') + taking regular exercise. Drinking excess alcohol= damage the liver (organ responsible for processing+breaking down alcohol) Smoking increases the risk of cardiovascular disease in several ways: financial cost for the NHS

Answer 346

result of changes in cells that lead to uncontrolled growth and division. person growing/ replacing old/damaged cells=new cells produced mitosis. sometimes begin divide uncontrollably. uneeded by body new cells produced= growth (tumour)

Answer 347

-treating patients with currently untreatable conditions -growing organs for transplants and research. -generate healthy cells, replace old diseased cells and tissue -increase understanding of how diseases occur and develop by experiment/observe organs/tissues made from stem cells -test new drugs on stem cells ———————————————————- -not guaranteed success -finding stem cell donors. -obtaining+storing embryonic stem cells- collected before birth -Mutations in stem cells cultured, some behave like cancer cells. -Cultured stem cells contaminated with virus, transferred to a patient. - to collect stem cell, kills embryo. Unethical+religious beliefs that life starts at embryo. -view as commodity, not a human -research carried out by commercial clinics, reported successes are not subject to peer review. -exploit with expensive treatments - false hope of a cure -only in developmental stage

Answer 348

-Inserted gene could inactivate important gene in patient’s genome>disrupts cell cycle>tumour - immune system attacks gene tech vector. Inflammation or organ failure -vector virus targets wrong cells. Damages healthy cell/ lead to cancer/illness -modified virus could recover their original ability to cause disease when introduced to body and cause infection ———————————————————- -Potential to eliminate and prevent hereditary disease e.g cystic fibrosis by switching off disease-causing gene and fixing mutated gene -treat range of disease e.g cancer and heart disease by replacing mutated genes -making diseased cells more evident to immune system. Improve body’s ability to fight disease

Answer 349

- more medicines, diagnosis, treatment ways - target disease with specific medicine - gene therapy to treat disease - faulty aloes repair - replacement with normal alleys - predict patient’s response to drug treatment for effectiveness - reduce use of ineffective drugs, saves limited NHS resources - certain effective different drugs can be prescribed to different patients with the same disease that was caused by different factors - identify faulty alleles and predict chance of them developing a disease and their offsprings inheriting it - sequencing DNA in cancer cells. Can be compared to human genome sequence to work out which genes mutated, gives them ideas for developing medicines - produce specific monoclonal antibodies targeting cancer cells that had the identified gene mutation

Answer 350

Causation - where action/factor directly causes outcome. correlation is a link/relationship. action/factor relates to outcome, but doesn't necessarily cause the other event to happen. If there is no scientific explanation then there is only a correlation. It cannot be shown that the factor causes the outcome, must be evidence that scientifically explains causation connection

GSCE Biology Flashcards

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