paper 2 Flashcards
(101 cards)
1
Q
practical 2.33B - investigate the energy content in a food sample
A
BANANA CHIP
- attach a boiling tube to a clamp stand
- Use the measuring cylinder to measure out 25cm3 of water and pour it into the boiling tube
- Record the starting temperature of the water using the thermometer
- Weigh the initial mass of the food sample
- Set fire to the sample of food using the bunsen burner and hold the sample 2cm from the bottom of the
boiling tube until it has completely burned - Record the final temperature of the water
- (Once cooled) weigh the mass of any remaining food and record
- Repeat the process with different food samples
A larger increase in water temperature indicates a larger amount of energy contained by the sample
We can calculate the energy in each food sample using the following equation:
Energy transferred (J) =
(mass of water (g) x 4.2 x temperature increase (°C)) ÷ (mass of food (g))
2
Q
how is water absorbed by the root hair cells
A
plants take in water from the soil through the root hair cells. the root hair cells (RHC) are specialized to increase their surface area which then increases rate of active transport.
the plant actively transports the mineral ions from the soil into the root hair cells. the mineral ions lower the water potential of the root hair cells. the water will then osmosis from the soil to the RHCs as the RHCs have the lower water potential. (osmosis - water moves from high to low conc)
this gradient is maintained as the water is continually being taken up by the xylem.
3
Q
transpiration
A
water lost from the leaves, mainly from the stomata due to evaporation off of the leaf surface
(water evaporates into the air spaces in the spongy mesophyll then diffuses out of the stomata)
4
Q
how is transpiration rate affected by humidity
A
Very humid air contains a great deal of water vapour – there is a smaller concentration gradient, so transpiration slows down.
In dry air the diffusion of water vapour from the leaf to the atmosphere will be rapid.
Transpiration therefore increases if humidity decreases.
5
Q
how is transpiration rate affected by wind speed
A
In still air, the region around a transpiring leaf will become saturated (full) with water vapour so that no more can escape from the leaf –causing transpiration to slow down.
In moving air, the water vapour will be blown away from the leaf as fast as it diffuses out. This will speed up transpiration.
Transpiration therefore increases as wind speed increases.
6
Q
how is transpiration rate affected by temperature
A
On a hot day, water will evaporate quickly from the leaves of a plant as the water molecules have more kinetic energy.
Transpiration therefore will increase as temperature increases
7
Q
how is transpiration rate affected by light intensity
A
Light itself does not affect evaporation, but in daylight the stomata of leaves are open to supply carbon dioxide for photosynthesis.
This allows more water to diffuse out of the leaves and into the atmosphere
8
Q
2.58B practical - investigate the role of wind in determining the rate of transpiration for a leafy shoot
A
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - place a hairdryer so its blowing on the plant to recreate wind
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
9
Q
2.58B practical - investigate the role of increased temperature in determining the rate of transpiration for a leafy shoot
A
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - make the room hot
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
10
Q
2.58B practical - investigate the role of humidity in determining the rate of transpiration for a leafy shoot
A
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - surround the plant in a clear plastic bag
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
11
Q
2.58B practical - investigate the role of light in determining the rate of transpiration for a leafy shoot
A
potometer!!
- The potometer must be set up under water - this prevents any air bubbles from entering the
system and blocking the xylem.. - Cut the stem of a shoot whilst submerging the shoot
- Put the shoot stem into the bung, grease the joint with plenty of petroleum jelly - this prevents
water loss and air entry - Put the bung into the potometer.
- Make sure the tap is closed and it is full of water (no bubbles). Then lift the potometer out of the
water. - Leave the end of the capillary tube out of the water until an air bubble forms then put the end
into a beaker of water. - make the room dark
- You can measure the transpiration rate as distance the bubble travels in five minutes (or the
time taken for the bubble to travel a set distance). You should take a number of readings and
calculate a mean rate.
12
Q
what does the kidney do
A
excrete toxic waste products and substances in excess
osmoregulation
13
Q
whats osmoregulation
A
the process of maintaining water and salt concentrations across membranes in the body
example of homeostasis
14
Q
what are the 3 parts of the kidney
A
cortex - the outmost region
Medulla - the inner section of the kidney
Renal pelvis - the tube linking the kidney to the ureter
15
Q
where are the nephrons
A
in the kidney
Nephrons start in the cortex of the kidney, loop down into the medulla and back up to the cortex
16
Q
where do the contents of the nephron go
A
drain into the renal pelvis and the urine collects there before it flows into the ureter to be carried to the bladder for storage
17
Q
structure of the nephron
A
The nephron is made up of a kidney tubule which has several sections:
glomerulus inside the bowman’s capsule
Proximal convoluted tubule
Loop of Henlé
Distal convoluted tubule
Collecting duct
18
Q
what is the proximal convoluted tubule
A
section of nephron after the bowmans capsule and before the loop of henle
19
Q
what is the distal convoluted tubule
A
section of nephron after the loop of henle and before the collecting duct
20
Q
how does the kidney excrete
A
Ultrafiltration
Selective reabsorption of glucose
Reabsorption of water and salts
21
Q
what is ultrafilterisation
A
Arterioles branch off the renal artery and lead to each nephron, where they form a knot of capillaries (the glomerulus) sitting inside the cup-shaped Bowman’s capsule
The capillaries get narrower as they get further into the glomerulus which increases the pressure on the blood moving through them (which is already at high pressure because it is coming directly from the renal artery which is connected to the aorta)
This eventually causes the smaller molecules being carried in the blood to be forced out of the capillaries and into the Bowman’s capsule, where they form what is known as the filtrate
This process is known as ultrafiltration
The substances forced out of the capillaries are glucose, water, urea, salts
Some of these are useful and will be reabsorbed back into the blood further down the nephron
22
Q
what is in the glomerular filtration
A
glucose, water, urea, salts
23
Q
selective reabsorption of glucose
A
After the glomerular filtrate enters the Bowman’s Capsule, glucose is the first substance to be reabsorbed at the proximal convoluted tubule
This takes place by active transport (by specialized cells)
The pct is adapted for this by having many mitochondria to provide energy for the active transport of glucose molecules
Reabsorption of glucose cannot take place anywhere else in the nephron as the gates that facilitate the active transport of glucose are only found in the proximal convoluted tubule
24
Q
whats in urine
A
water, urea, ions
25
what happens in the loop of Henle
Salts are reabsorbed by diffusion and active transport as well as water by osmosis
also makes the medulla salty which makes osmosis more efficient
26
what is absorbed in the distal convoluted tubule
mineral ions reabsorbed
K Na Ca
27
2.14B practical: investigate how enzyme activity can be affected by changes in pH
amylase digests starch
1. mix 10cm of 10% starch solution with 5cm of 5% amylase in a boiling tube.
2. add in a few drops of a solution with a specific pH
3. every 10s add 1 drop of this solution to 1 drop of iodine in a spotting tile
4. repeat using different pH solutions
when the starch has been fully digested (so none is present) iodine will stay orange
when the iodine stays blue it shows the enzyme has been denatured as it is not capable of breaking down the starch so the starch is still present giving a positive test result.
28
what is the role of diffusion in gas exchange
in single celled organisms gases can exchange sufficiently by just diffusing straight through the cell membrane
in multi celled organisms, there are exchange surfaces and organ systems that maximise the exchange. eg lungs or leaves
gain nutrients in the digestive system
gain oxygen in the lungs
remove waste products in the lungs and kidneys
29
what is gas exchange
the exchange of gases from an organism to the enviroment or vice versa
30
how is the gas exchange of CO2 and O2 related to respiration and photosynthesis (in plants)
plants need O2 and CO2 for respiration and photosynthesis.
FOR RESPN
the O2 diffuses from a high conc outside the leaf to a lower conc inside the leaf.
the CO2 diffuses from a high conc inside the leaf to a lower conc outside the leaf
the reverse happens for photosynthesis
31
how is the structure of leaves adapted for gas exchange
adapted to maximise gas exchange of CO2 (released in respiration but used in photosynthesis), O2 (released in photosynthesis but used in respiration) and water vapour (released in respiration and transpiration)
adaptation of whole leaf
- thin leaves which give short diffusion distance
- flat leaves which provide a large surface area to volume ratio
- leaves have many stomata which allow movement of gases in and out of the air spaces by diffusion
adaptations of specific bits
- leaves contain air spaces which allow gas movement around the other mesophyll cells and a shorter diffusion distance
- stomata can open and close allowing CO2 in when there is sunlight for photosynthesis and then shut when there is no sunlight to stop excess loss of water
- upper epidermis is transparent which allows light to penetrate to the palisade mesophyll
- palisade cells are long, thin and tightly packed. They contain large numbers of chloroplasts. This maximises absorption of sunlight energy. (palisade mesophyll is main site of photosynthesis)
- xylem transports water absorbed in roots to the leaves which provides a short diffusion distance for the water to move into the photosynthesis cells
- spongy mesophyll are loosly packed creating air gaps. they also are coated in a thin layer of water which allows the gases to dissolve
32
what is the role of the stomata in gas exchange
stomata open to allow CO2 to diffuse into the leaf for photosynthesis. they also allow other gases to diffuse in and out
stomata will also close when there is little light as the plant has no need for CO2 for photosynthesis as there is not enough light to allow the process to happen. they will also close when there is little water as water will diffuse out or conditions that allow water to diffuse out quickly (windy or hot or dry air) if they are open
33
how do guard cells work
the guard cell opens and closes the stomata by actively transporting ions into GCs cytoplasm, then the ions lower the water potential making water to move in making the cell turgid so the stomata open
In the light the guard cells photosynthesise. The concentration of sugars increases, the water potential in the guard cells falls and so water moves into the guard cells by osmosis. They become turgid (swollen) - this causes the guard cells to become banana shaped, due to the inflexible inner cell wall, and opens the stomata.
Photosynthesis stops in the dark. As the sugar concentration falls (due to respiration), water potential increases and water moves out of the guard cells. They become flaccid and the stomata close.
34
what is the net exchange of O2 and CO2 during the day and night
Plants can only photosynthesise when they have access to light, however, cells respire all the time
This means that gas exchange in plants varies throughout a 24 hour period
During the daytime plants both respire and photosynthesise
The rate of photosynthesis tends to be higher than the rate of respiration (unless there is a low light intensity)
Therefore there is net diffusion of carbon dioxide into the plant and net diffusion of oxygen out of the plant during the day
During the nighttime, plants only respire
This means that there is a net movement of oxygen into the plant and net diffusion of carbon dioxide out of the plant during the night time
At low light intensities, the rate of photosynthesis is equal to the rate of respiration
This means that there is no net movement of oxygen or carbon dioxide in either direction
35
2.45B practical: investigate the effect of light on net gas exchange from a leaf, using hydrogen-carbonate indicator
Measure out 20 cm3 hydrogencarbonate indicator into 4 boiling tubes
Put some cotton wool into each boiling tube
Label the boiling tubes A-D and set them up as follows:
Tube A - No leaf (control tube)
Tube B - Place a leaf in the tube and leave in the light
Tube C - Place a leaf in the tube and wrap it in aluminium foil to block out the light
Tube D - Place a leaf in the tube and wrap it in gauze to allow partial light
Put a bung into the top of each tube
Leave all 4 tubes in the light for 30 minutes
After 30 minutes, we would expect the following results:
Tube A - The control tube should remain an orange/red colour to show that the carbon dioxide is at atmospheric levels
There has been no net movement
Tube B - This tube was placed in the light with a leaf which is photosynthesizing and respiring
Because the rate of photosynthesis is greater than the rate of respiration, the hydrogencarbonate indicator will turn purple as there is less carbon dioxide than atmospheric levels
Tube C - This tube had a leaf inside, but was wrapped in aluminium foil meaning that no sunlight could reach the leaf
No light means that this leaf will not photosynthesize but will still be respiring and therefore producing carbon dioxide. The indicator will turn yellow as carbon dioxide levels increase above atmospheric levels
Tube D - This tube had a leaf inside and was wrapped in gauze allowing partial light
This means that the rate of photosynthesis equals the rate of respiration so there was no net change in carbon dioxide levels and the indicator remained orange/red
36
what is the role of platelets
Platelets cause blood to clot when the skin is cut which prevents pathogens or microorganisms entering and also stops blood loss
Platelets are fragments of cells
When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding
A series of reactions occur within the blood plasma
Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot
The clot eventually dries and develops into a scab to protect the wound from bacteria entering
Scab formation seals the wound with an insoluble patch that prevents entry of microorganisms that could cause infection
It remains in place until new skin has grown underneath it, sealing the skin again
37
waste products and their loss from the stomata
Oxygen and carbon dioxide can be both reactants and waste products within a plant
The amount or intensity of light affects the waste products within plants
During the day, when there is sufficient light:
The rate of photosynthesis is higher than the rate of respiration
More oxygen is released than used in respiration
Less carbon dioxide is released than used in photosynthesis
Net effect - oxygen is in excess and a waste product
During the night, when there is insufficient light:
There is no photosynthesis, only respiration
Oxygen is used in respiration and carbon dioxide is produced
No photosynthesis means that no carbon dioxide is used
Net effect - carbon dioxide is in excess and a waste product
Whichever gas is in excess diffuses out of the plant via the leaf organ
The gases exit through the stomata
38
structure of urinary system
blood goes through the kidneys where urea and other substances are filtered out.
these substances are transported through the ureters into the bladder
then they are transported via the urethra which carries urine to the outside
39
how is water reabsorbed in the blood from the collecting duct
collecting duct responds to ADH to vary how much water is reabsorbed
When ADH binds to receptors on the principal cells of the collecting duct, vesicles containing aquaporins fuse with the cell membrane. These aquaporins are protein channels that increase the permeability of the collecting duct, allowing more water to be reabsorbed into the blood by osmosis
40
what is the role of ADH
If the water content of the blood is too high then less water is reabsorbed, if it is too low then more water is reabsorbed
This is controlled by the hormone ADH
Any change to the water level of the blood is detected by the hypothalamus, which then sends a signal to the pituitary gland
The pituitary gland in the brain constantly releases a hormone called ADH
How much ADH is released depends on how much water the kidneys need to reabsorb from the filtrate
ADH affects the permeability of the tubules to water
If the water content of the blood is too high:
The pituitary gland releases less ADH which leads to less water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become less permeable to water)
As a result, the kidneys produce a large volume of dilute urine
If the water content of the blood is too low:
The pituitary gland releases more ADH which leads to more water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become more permeable to water)
As a result, the kidneys produce a small volume of concentrated urine
41
source, role and effect of ADH
produced in the pituitary gland (brain)
targets the kidney (collecting duct)
effect - causes water to be reabsorbed by increasing the permeability of the collecting duct
42
source, role and effect of FSH
produced in pituitary gland (brain)
targets the ovaries
causes the egg to mature and stimulates oestrogen production
43
source, role and effect of LH
produced in the pituitary gland (brain)
targets the ovaries
triggers ovulation and the release of progesterone
44
what is a stem cell
an unspecialised cell which can differentiate and divide into many types of cells but also just mitotically divide into more stem cells
can be found inside long bones, embryos and in plants
45
importance of cell differentiation in the development of specialised cells
how cells develop the structure and characteristics needed to be able to carry out their functions
undifferentiated cells receive signals which stimulates the transcription of certain genes allowing them to become specialised (so they can carry out specialised functions)
46
advantages of using embryotic stem cells in medicine
(very early stages of an (embryo) fertilised egg as it begins to divide a few times)
can differentiate into any type of cells and divide mitotically
scientists can collect them and grow them in a lab and then instruct which genes to be transcribed to decide how they are specialised allowing them to become whatever type of cell is needed for the transplant
47
disadvantages of using embryotic stem cells in medicine
ethical issues with using them as they can be sourced from unused embryos produced from IVF and these embryos could have turned into humans
as embryo is not from patient the patients body may reject the embryotic cells (as the embryo cells have different antigens then the patient which causes WBCs to recognise them as foreign and so the WBCs will kill the cells) which can result in failure of medicine or the patient may have to take immune suppression medication which could cause other illness
48
advantages of using adult stem cells in medicine
comes from your own body so the antigens from the stem cells will match the ones from the rest of your body so less likely to be rejected
no ethical concerns
less likely to become cancerous
49
disadvantages of using adult stem cells in medicine
can only differentiate into some cells (eg bone marrow stem cells can only become blood or bone cells)
don't multiply as much as embryotic ones
if the patient is older the cells are less effective as they may have degenerated
50
medical uses of stem cells
can be used to repair damaged tissues and grow new organs for transplant and treat diseases
diabetes - stem cells can be differentiated into insulin producing cells which can be put into the patients body so they can produce insulin
51
difference between antigen and antibody
antigen is a molecule found on the surface of a cell (unique to each cell)
antibody is a protein made by lymphocytes which is complementary to an antigen which attaches to the antigens and clumps the cells together
52
how does a vaccination work
used to induce immunity to an infectious disease
vaccine contains harmless version of a pathogen (either already killed, only fragments of cells or prevented from dividing)
vaccine in injected
once vaccine is in blood stream then antigens from the vaccine trigger an immune response
some Lymphocytes recognise the antigens in the bloodstream
The activated lymphocytes produce antibodies specific to the antigen encountered
Memory cells are produced from the lymphocytes
Memory cells and antibodies subsequently remain circulating in the blood stream so if the actual pathogen enters the body the lymphocytes produce antibodies much faster
53
immune response to a pathogen
The pathogen enters the blood stream and multiplies
A release of toxins (in the case of bacteria) and infection of body cells causes symptoms in the patient
Phagocytes that encounter the pathogen recognise that it is an invading pathogen and engulf and digest (non-specific response)
Eventually, the pathogen encounters a lymphocyte which recognises its antigens
The lymphocyte starts to produce specific antibodies to combat that particular pathogen
The lymphocyte also clones itself to produce lots of lymphocytes (all producing the specific antibody required)
Antibodies stick pathogens together and prevent reproduction
Phagocytes engulf and digest the destroyed pathogens
54
what is the role of LH in the menstrual cycle
ovulation - follicle on ovary releases mature egg in oviduct
remnant of follicle on ovary becomes corpus luteum
55
what is the role of FSH in the menstrual cycle
follicle develops and egg matures
maturing follicle releases oestrogen
56
what is LH
luteinising hormone
57
what is FSH
follicle-stimulating hormone
58
structure of a DNA molecule
DNA (deoxyribonucleic acid) is a polymer made up of 2 strands coiled around each other to make a double helix where the strands are linked by a series of paired bases: adenine (A) with thymine (T), and cytosine (C) with guanine (G)
59
structure of a RNA molecule
RNA (ribonucleic acid) is made of a single polynucleotide strand and contains the nitrogenous bases: adenine, guanine, cytosine and Uracil
it is made of many nucleotides linked together in a long chain
60
what does codominance mean
when both alleles within a genotype are expressed in the phenotype of an individual
eg a red petal flower with a white petal flower becomes a pink petal flower
61
Transcription
occurs in the nucleus of the cell and it is where a copy of a section of DNA is made
order:
part of the DNA molecule unwinds when the hydrogen bonds between the complementary base pairs break
the template strand of the gene which codes for the protein which is being copied is now exposed
Free mRNA (messanger RNA) nucleotides that are present bind to the exposed nucleotides (bases) on the template strand using the base pair rule
The mRNA nucleotides join together to form a single strand of mRNA
the mRNA leaves the nucleus via a pore
the new strand of mRNA is now a complimentary copy of the orginal DNA (opposite bases)
62
Translation
occurs in the cytoplasm of the cell and produces a chain of amino acids which form a protein
order:
once the mRNA has left the nucleus it attaches to a ribosome
in the cytoplasm, there are free molecules of tRNA (transfer RNA) which have an unpaired base on one end (anticodon) an a corresponding amino acid on the other
the anticodon on each tRNA pairs with a complementary codon on the mRNA and brings the amino acid with it
other tRNA connect to other parts of the mRNA and a peptide bond is formed between the neighboring amino acids
this continues until a 'stop' codon on the mRNA is reached as this signals for the translation to stop as the amino acid is complete
the amino acid chain is then folded and modified into the final protein molecule
63
order of protein synthesis
transcription
mRNA attaches to a ribosome
translation
64
how does a change in the DNA affect the phenotype
as the DNA base pairs determine the sequence and type of amino acids which make up a protein, if the pairs change, then there will be different amino acids or they will be arranged in a different order which will result in a different protein being made
65
substitution mutation
where one letter swaps to another eg. A to C
option 1: codes for the same amino acid so there is no affect
option 2: codes for a different amino acid but it is far away from the active site so there is no affect
option 3: codes for a different amino acid which is near the active site which prevents the substrate binding - negative mutation
option 4: codes for a stop codon which will mean the protein isn't made at all - very negative
66
addition mutation
adds in a letter which then causes a frame shift which is very bad as all the amino acids change as the triplets are now different making completely different protein
stop codon may also be created in the wrong place also causing wrong protein.
67
deletion mutation
adds in a letter which then causes a frame shift which is very bad as all the amino acids change as the triplets are now different making completely different protein
stop codon may also be created in the wrong place also causing wrong protein.
68
do most genetic mutations effect the phenotype
no as most of them either don't change the amino acid or the change occurs far away from the active site so the function of the protein does not change therefore no effect on the phenotype.
rarely the new DNA will change the allele and create a new one which may be good or bad however either way this will change the phenotype
69
what factors can increase the chance of mutations
mutations happen spontaneously and continuously but can be increased in some ways
Exposure to:
gamma rays, x-rays and ultraviolet rays (all types of ionising radiation that can damage bonds and cause changes in base sequences)
Chemical mutagens (chemicals in tobacco such as tar)
increased rates of mutation can cause cells to become cancerous
70
what does biodiversity mean
The measure of how many different species live in an ecosystem
71
4.4B practical - investigate the distribution of organisms in their habitats and measure biodiversity using quadrats
1. Use 2 tape measures to lay out your first survey area (e.g. 10m X 10m)
2. Use a random number generator to create a set of coordinates to place your first quadrat
3. Count the number of different species and the number of each species found within that quadrat
4. Repeat this process until you have collected the data for 10 quadrats
5. Repeat these steps for the second survey area
the area with the greatest number of different species and the number of each species
72
what is the role of the nitrogen fixing bacteria
takes N2 gas and change it into nitrates in the soil
73
what is the role of decomposers
When the animals and plants die, they decay and all the proteins inside them are broken down into ammonium compounds and put back into the soil
74
what is the role of nitrifying bacteria
convert the ammonium compounds (from the decomposers) to nitrites and then to nitrates
75
what is the role of denitrifying bacteria
take the nitrates out of the soil and convert them back into N2 gas
76
why can't animals and plants absorb nitrogen out of the air
N2 gas is very stable and the bonds holding the nitrogen atoms together would need massive amounts of energy to break (the two nitrogen atoms in a nitrogen molecule are held together by a triple covalent bond)
77
why do we need nitrogen
Nitrogen as an element is required to make proteins
78
what is nitrogen fixing
nitrogen taken out of the air and converted into something easier to absorb such as nitrates
79
what nitrogen fixes
lightning
nitrogen fixing bacteria
80
how does lighting nitrogen fix
splitting the bond between the two atoms and turning them into nitrous oxides like N2O and NO2 that dissolve in rainwater and ‘leach’ into the soil
81
how does the fixed nitrogen get removed from the soil
denitrification (bad denitrifying bacteria)
plants actively transport N ions into their roots
82
how does nitrogen get put into the soil
nitrogen fixing (lighting or nitrogen fixing bacteria)
nitrification (nitrifying bacteria)
83
how do animals get nitrogen
eat the plants (or other animals) which contain amino acids and proteins
84
how do plants get nitrogen
plants actively transport N ions into their roots
85
how do animals get rid of the nitrogen
waste (urine and faeces) which puts the nitrogen back into the soil as ammonium compounds
86
how does denitrifying bacteria work
they are found in poorly aerated soil which mean they respire anaerobically which puts the nitrogen straight out of the soil and into the air again
87
how to prevent denitrifying bacteria
by ploughing and turning over soil (aerating)
88
effects of deforestation
leaching - if there is deforestation then there are less trees to uptake water so the water runs off into lakes and rivers. This means the mineral ions are removed from the soil and some of these nutrients (especially nitrates), can lead to further problems such as eutrophication
soil erosion - The water running off from deforested areas may carry away some of the topsoil, causing erosion. Because of deforestation there are no plants present in the soil and therefore there are no roots holding the soil in place. The topsoil contains the most fertile, mineral ion rich materials: when it is lost due to erosion the minerals are also lost, making the land very difficult to use for crop growth and reducing the chance of plants re-growing.
evapotranspiration - water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants. Transpiration is the evaporation and diffusion of water through the stomata of leaves. This evaporated water moves into the atmosphere and eventually (through the water cycle) makes rain in rain clouds. These rain clouds when then rain onto the plants, and the cycle will continue. When deforestation occurs, this cycle is broken.
carbon cycle - trees photosynthesis and so when you cut them down they can't meaning that less carbon dioxide gets converted back into oxygen breaking the cycle. The cut down trees are usually burnt aswell which adds more carbon back into the atmosphere
imbalance of atmospheric gases - more CO2 in atmosphere and less O2 as trees don't photosynthesis as they are cut down
89
advantages of fish farming
raises a lare number of fish in a small area
allows for selective breeding
protection against predators
can control water quality
control feeding
90
fish farming water quality method
water is filtered to remove waste and harmful bacteria which prevents diseases
water is also cleaned to maintain high levels of O2 for aerobic respiration
91
fish farming control of intraspecific predation method
fish are seperated based on size and age so to minimize the chance of them eating each other
92
fish farming control of interspecific predation method
different species are seperated by nets and tanks to prevent fighting
93
fish farming control of disease method
antibiotics are given to fish as well as fish being kept in small numbers to stop disease spread
94
fish farming removal of waste products method
water is filtered to remove faeces and sewage and the tanks are cleaned
95
fish farming feeding method
fish are fed food that is high in nutrients to ensure fast growth
fed little and often to not waste food and prevent them over eating or eating each other
96
fish farming use of selective breeding method
fish are seperated by gender so that farmers can selectively breed
97
process of cloning an animal
take a nucleus (diploid as from adult body cell) from the animal you want to clone
insert taken nucleus into enucleated (empty) egg cell using a micropipette
electric shock the now full egg cell
shock causes mitosis to begin in the egg
once egg has replicated enough to form an embryo, insert into uterus of carrier animal (surrogate mother)
98
how can cloned transgenic animals be used to produce human proteins
transgenic organism contains an foreign gene in its DNA (human protein gene)
This foreign gene causes the animal to produce a useful compound which gets expressed within its milk when it is bred
99
what is micro propagation
how plants are cloned also called tissue culture
100
method of micropropagation
cut off a growing tip from a healthy parent plant
dip tip into a sterilising fluid to kill any bacteria or fungi present
cut tip into many pieces
each piece is placed in a test tube containing sterilised agar (contains nutrients needed for plant to grow) jelly which is sloped diagonally to prevent any condensation produced to not drown the plant
once plant has grown enough plant in soil
101
how can micropropagation be used to produce commercial quantities of genetically identical plants
It allows a variety of a plant with desirable characteristics to be produced:
Cheaply
With a greater yield (a large number of plants can be produced per square metre)
Quickly (the plantlets are ready to grow into mature plants)
At any time of the year
Identical to each other (so they retain the desired characteristic)
Disease-free or resistant plants can be bred
