Biology Flashcards
(385 cards)
1
Q
Explain the characteristics of a light microscope.
A
- Uses a beam of light to form an image.
- Can magnify objects up to 2000 times. (School ones usually only go up to 400 times.)
- Can be used to view living objects.
- Relatively cheap and easy to move around.
2
Q
Explain the characteristics of an electron microscope.
A
- Uses a beam of electrons to form an image.
- Can magnify objects up to 2,000,000 (2 million) times.
- Cannot be used for living objects.
- Very expensive and need to be kept in special conditions.
3
Q
Which type of microscopes are usually used in schools?
A
Light microscopes.
4
Q
What does resolving power mean for a microscope?
A
The measure of how close 2 dots can be distinguished through a microscope on an object.
5
Q
What is the equation for magnification?
A
Magnification = image size / object size
6
Q
What is the purpose of a nucleus?
A
To control the cell’s activities and contains DNA
7
Q
What is contained in the nucleus of a cell?
A
Genes on chromosomes which carry instructions for making proteins.
8
Q
What is the purpose of cytoplasm?
A
A liquid gel in which organelles are suspended, also the site of many chemical reactions.
9
Q
What is the purpose of the cell membrane?
A
To control movement of substances into and out of the cell.
10
Q
What is the purpose of the mitochondria?
A
Site of energy transfer for aerobic respiration.
11
Q
What is the purpose of ribosomes?
A
Organelle where protein synthesis takes place.
12
Q
What is the purpose of cell walls?
A
A cellulose structure to provide structure to the cell.
13
Q
What is the purpose of chloroplasts?
A
They contain chlorophyll for photosynthesis.
14
Q
What is the purpose of the permanent vacuole?
A
To contain cell sap, keeping the cell rigid and helps support the plant.
15
Q
What organelles are found in animal cells?
A
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribosomes
16
Q
What organelles are found in plant cells?
A
- Nucleus
- Cytoplasm
- Cell membrane
- Mitochondria
- Ribsomes
- Cell wall
- Chlorophyll / Chloroplast
- Permanent vacuole.
17
Q
What is the difference between a eukaryotic and prokaryotic cells?
A
Eukaryotic cells contain a nucleus holding genetic material, whereas prokaryotic cells have plasmids (DNA loops) containing genetic material. Prokaryotic cells are also smaller than eukaryotic cells.
18
Q
What do nerve cells do?
A
Carry electrical impulses around the bodies of animals.
19
Q
What are the adaptations of a nerve cell?
A
- Dentrites to make connections to other nerve cells.
- An axon to carry the impulse from one place to another.
- Nerve endings or synapses which pass impulses to other cells by producing transmitter chemicals.
- Many mitochondria in synapses to transfer the energy needed to make transmitter chemicals.
20
Q
What do muscle cells do?
A
They contract and relax to move around your body.
21
Q
What are the adaptations of a muscle cell?
A
- Special proteins that slide over each other.
- Many mitochondria to transfer the energy required for chemical reactions.
- A store of glycogen which can be broken down and used in respiration to transfer energy.
22
Q
What do sperm cells do?
A
Carry genetic information from the male parent to the female parent. (The egg.)
23
Q
What are the adaptations of a sperm cell?
A
- Long tail (flagellum) which whips side to side to move the sperm.
- A middle section full of mitochondria to transfer energy needed by the flagellum to move.
- An acrosome to store digestive enzymes to break down the outer layers of the egg.
- A large nucleus to contain genetic information.
24
Q
What do root hair cells do?
A
Absorb water and mineral ions in the soil.
25
What are the adaptations of a root hair cell?
- Large surface area for quick abosorbing.
- Large permanent vacuole to speed up movement of water through osmosis.
- Many mitochondria to transfer the energy required for active transport.
26
What do photosynthetic cells do?
Absorb sunlight to make food.
27
What are the adaptations of a photosynthetic cell?
- Chloroplasts to trap light for photosynthesis.
- Continuous layers in the leaf and outer layers of the stem.
- Large permanent vacuole to keep the cell rigid.
28
What do xylem cells do?
Transports water and mineral ions from the roots to the stem and leaves. It also contains xylem tissues which supports the plant.
29
What are the adaptations of a xylem cell?
- Long hollow tubes for water and mineral ions to move up.
- Spirals and rings of lignin to make the tubes of xylem very strong.
30
What does the phloem cell do?
Tissue which transports food made by photosynthesis to the rest of the plant.
31
What is diffusion?
Movement of particles from an area of high concentration to an area of low concentration, along the concentration gradient.
32
What is osmosis?
Movement of water from a dilute to concentrated solution.
33
What is active transport?
Movement of particles from an area of low concentration to an area of high concentration. Going against the concentration gradient.
34
Which one(s) require energy out of:
1) Diffusion
2) Osmosis
3) Active transport
1) No energy
2) No energy
3) Requires energy
35
What is the word for 2 solutions with the same concentrations?
Isotonic
36
What does isotonic mean?
2 solutions with the same concentration.
37
What is the word for a solution with higher concentration?
Hypertonic.
38
What does hypertonic mean?
A solution with a higher concentration.
39
What is the word for a solution with a lower concentration (dilute)?
Hypotonic
40
What does hypotonic mean?
A solution with a lower concentration.
41
What is turgor pressure?
When no water can enter a cell due to the pressure inside.
42
What is plasmolysis?
When the cell membrane pulls away from the cell wall.
43
What is cystic fibrosis?
When a person produces abnormally thick mucus because the active transport system in their mucus cells aren't working properly.
44
Where is oxygen inhaled into?
The alveoli in the lungs.
45
What is the stomata in plants?
Tiny openings (pores) in plant tissues which allow gas exchange.
46
Where is villi found and what does it do?
It is found in the small intestine and it uses it's large surface area to absorb food molecules.
47
What is mitosis?
When a cell splits into 2 identical cells.
48
Why is mitosis important?
It allows living organisms to grow, but also allows body repairs and replacing cells that have died.
49
What is the cell cycle?
The steps in the process of cell division. (Mitosis.)
50
What are the 3 stages of the cell cycle?
**1)** Cell grows and DNA (chromosomes) replicate. Increase in number of sub-cellular structures
**2)** Complete set of chromosomes is pulled to each end of the cell. Nucleus divides to create 2 nuclei (mitosis)
**3)** Cytoplasm and cell membrane divides to form 2 identical daughter cells
51
How many pairs of chromosomes do human body cells have?
23 pairs of chromosomes.
(Or 46 singular chromosomes.)
| (23 come from the female parent, and 23 come from the male parent.)
52
How many chromosomes do egg cells and sperm cells have each in humans?
23 chromosomes.
| (They combine to form 46 chromosomes, enough for a normal body cell.)
53
What is cell differentiation?
When a cell changes into different types of cells to carry out functions.
| (i.e. they specialise.)
54
What are unspecialised cells called?
Stem cells
55
What is a meristem?
An actively dividing plant tissue.
56
What is cloning?
Producing genetically identical offspring.
57
Why is it difficult to clone animals?
Because once cells are differentiated, they cannot become unspecialised again.
58
What is a zygote?
The product of an egg cell and sperm cell fusing. The zygote divides many times to form a ball of cells, known as an embryo.
59
Where can adult stem cells be found?
In the bone marrow.
60
What conditions can human stem cells be used to treat?
- Paralysis by differentiating stem cells into nerve cells.
- Macular degeneration in the eye to restore lost vision.
- Diabetes, by producing cells which are sensitive to blood sugar and can produce insulin.
61
What are the benefits of cloning plants?
- Rare plants can be saved from extinction.
- Large populations of plant species can be produced for research.
- Large numbers of exotic plants can be produced for sale.
- Plants can be produced with special features such as disease resistance.
62
Where are embryonic stem cells found?
In the inner layers of the ball of cells which forms an embryo.
63
Where are stem cells found in plants?
In the meristems
64
What are some of the issues from stem cell production?
- Some people believe that taking stem cells from an embryo is violating its rights.
- Some people, usually in religions, believe that producing stem cells is interfering with the natural process of reproduction.
- Some people think that money is being wasted on stem cell research.
- Scientists find it difficult to 'persuade' stem cells to differentiate, development is slow and expensive.
- Embryonic stem cells divide rapidly and there are fears that it could cause cancer.
- Adult stem cells could transmit viruses or trigger and immune response.
65
What is therapeutic cloning?
The process of producing an embryo with genes which are identical to the patient, and then using embryonic stem cells for medical treatment.
66
What is an advantage of theraputic cloning?
The cells produced are genetically identical to the patient so they are less likely to be rejected.
67
What is a tissue?
A group of cells with similar structures and functions which work together to carry out a task.
68
Name the 4 types of tissues in animals and their function.
1) Muscular: movement.
2) Glandular: production of enzymes and hormones.
3) Epithelial: covering the outsides of organs and structures.
4) Connective: supports, protects and provides structure to other tissues and organs.
69
What is an organ system?
A group of organs working together to carry out a task.
| (For example, the digestive system.)
70
What does the digestive system do?
Changing food that you eat from insoluble molecules to soluble molecules, then absorbing them into the blood.
71
Where is bile produced and where is it stored?
It is produced in the liver and stored in the gall bladder.
72
What does the small intestine do?
Helps further digest food from the stomach, then absorbs nutrients through the villi.
73
What does the large intestine do?
Absorbs remaining water
74
What are some adaptations of villi?
- Very large surface area.
- Thin wall for short diffusion path.
- Good blood supply to carry food away to maintain a concentration gradient.
75
What are carbohydrates made of?
Units of sugar
76
What are lipids?
Molecules made from 3 molecules of fatty acids linked to a molecule of glycerol.
77
What are proteins made of?
Long chains of amino acids.
78
What is an enzyme?
A biological catalyst. They speed up reactions.
79
What is an active site?
The area of an enzyme where substrates fit.
| (Specific molecules can fit in each active site. Lock and key theory.)
80
What can enzymes do to substrates?
- Build large molecules from many small ones, such as building starch from glucose molecules.
- Change one molecule into another, such as converting sugars.
- Break down larger molecules into smaller ones.
81
What is metabolism?
The sum of all chemical reactions that take place in the body. These reactions break and/or build up molecules.
82
What is denaturing in enzymes?
When the temperature gets too high, the shape of the active site changes. This will slow down or completely stop an enzyme from functioning as substrates won't be able to fit in the active site.
83
What is the effect of pH on an enzyme?
If the pH is too high or too low, the forces which hold together the proteins in an enzyme weaken and the enzyme changes shape. This will denature the enzyme.
84
What are the 3 words used to describe pH?
1) Acidic
2) Neutral
3) Alkaline
85
What are the 3 digestive enzymes?
1) Amylase (carbohydrase)
2) Proteases
3) Lipase
86
What temperature to enzymes work best at?
37°C
(Body temperature)
87
What does bile do?
- Neutralises stomach acid.
- Makes the small intestine slightly alkaline.
- Emulsifies fats (breaking down fats into smaller droplets) to increase surface area.
88
What are the contents of blood?
- Plasma
- Red blood cells
- White blood cells
- Platelets
89
What does plasma do in the bloodstream?
It is the watery fluid which holds all the components of blood flow.
90
What do red blood cells do?
It uses haemoglobin to bind with oxygen so that it can be carried around the body.
91
What do white blood cells do?
They form the body's defence system against microorganisms.
92
What do platelets do?
They help clot blood at the site of a wound.
93
What are the adaptations of a red blood cell?
- Bioconcave discs for large surface area.
- Red pigment called haemoglobin to bind with oxygen which forms oxyhaemoglobin.
94
What do arteries have and do?
- Carry blood away from the heart at a high pressure
- They have thick walls containing muscles and elastic tissues.
- Small lumen
95
What are the 3 types of blood vessels?
- Arteries
- Veins
- Capillaries.
96
What do veins have and do?
- Carry blood towards the heart at a low pressure
- Thin walls
- Large lumen
- Contain valves to prevent backflow.
97
What do capillaries have and do?
- Carries blood to tissues and cells
- Connects arteries and veins
- One cell thick for short diffusion path
- Very narrow lumen
98
What is a double circulatory system?
**A blood transportation system with 2 parts.**
One carrying blood to the lungs and back to the heart to collect oxygen. And another to carry oxygenated blood to your organs and back to the heart.
99
What are the 4 chambers of the heart and where would they be on a diagram?
- Right atrium (top left)
- Left atrium (top right)
- Right ventricle (bottom left)
- Left ventricle (bottom right)
100
What does the right atrium do?
Receives deoxygenated blood from the body from the vena cava.
101
What does the left atrium do?
Receives oxygenated blood from the lungs from the pulmonary vein.
102
What does right ventricle do?
Pumps deoxygenated blood into the pulmonary artery to the lungs.
103
What does the left ventricle do?
Pumps oxygenated blood into the aorta to be transported around the body.
104
What stops blood from flowing in the wrong direction?
Valves
105
What do the coronary arteries do?
Supplies the heart muscles with oxygenated blood.
## Footnote
(If it is blocked, or narrowed, it will likely cause coronary heart disease.)
106
How do doctors open up arteries?
With a stent.
107
What could leaky valves potentially do?
Blood could flow in the wrong direction. (Backflow)
108
What is the beats per min of a pacemaker and where would it be located?
70 beats per min.
Located in right atrium.
109
What are artifical hearts used for?
- Keeping patients alive while waiting for a heart transplant.
- Allowing heart to rest as an aid to recovery.
110
What is a disadvantage of artificial hearts?
The patient needs drugs to prevent the blood from clotting.
111
What are the adaptations of alveoli?
- Large surface area
- Thin walls for short diffusion path
- Good blood supply
112
Where does oxygen diffuse into after the alveoli?
Capillaries in the lungs.
113
What is a palisade mesophyll?
A plant tissue which has many chloroplasts and can photosynthesise.
114
What is a spongy mesophyll?
A plant tissue with some chloroplasts, but many air spaces between cells and a large surface area for diffusion of gases.
115
What is translocation?
When the phloem tissue in a plant carries dissolved materials from the leaves to the rest of the plant.
116
What are the 2 transportation tissues in plants?
- Xylem
- Phloem
117
What does a guard cell do?
Controls the size of the stomata in plants, therefore, changing the rate of gas diffusion.
118
What is transpiration?
When water vapour diffuses out of the plant through the stomata.
119
What 4 factors affect rate of photosynthesis and how?
- **Temperature.** When temperature increases, molecules move faster, making rate of diffusion faster too.
- **Humidity.** The rate of diffusion of water is quicker in dry air than damp air.
- **Wind.** Windy conditions increase rate of evaporation and blow away water vapour, increasing concentration gradient.
- **Light intensity.** More light increases rate of photosynthesis.
120
How do plants control water loss?
- Waxy, waterproof cuticles on leaves.
- Most of the stomata are under the leaves.
- Wilting, as surface area will decrease.
- Stomata can close which can reduce water loss but also reduce rate of photosynthesis.
121
What is a communciable disease?
A disease which can be spread from one organism to another.
122
What is a non-communicable disease?
A disease which cannot be spread from one organism to another.
123
What factors can affect health?
- Diet
- Stress
- Living conditions
- Gender
- Financial status
- Ethnicity
- Number of people in contact with
124
Where do viruses live in the body?
Inside cells.
125
What is a pathogen?
A microorganism which can cause disease.
126
What are the 4 types of pathogens?
- Virus
- Bacteria
- Fungi
- Protist
127
How does bacteria make you feel ill?
Producing toxins in the body and potentially damaging body cells.
128
How do viruses harm us?
They reproduce inside cells, damaging and destroying them.
129
How can pathogens be spread?
- Through the air
- Direct contact
- Through water
130
What is binary fission?
The process by which prokaryotic cells such as bacteria divide.
131
What is agar gel used for?
A substance which acts as a culture, containing nutrients, for the growth of bacteria and other microorganisms
132
Why should microorgansims be prevented from leaving the petri dish?
In case there is a mutation, producing a new and dangerous pathogen.
133
In what ways can bacterial growth be prevented?
- Raising or lowering temperature
- Disinfectants
- Antiseptics
- Antibiotics
134
Who discovered that infections could be transferred and what did he tell people to do to help prevent this?
**Ignaz Semmelweiss**
He told his staff to wash their hands between treating patients.
135
Who showed that microorganisms can cause disease and what did he develop afterwards?
**Louis Pasteur**
He developed vaccines against anthrax and rabies.
136
In what ways can the spread of communicable diseases be prevented?
- Good hygiene
- Isolating infected people
- Destroying or controlling vectors
- Vaccinations
137
What is the main symptom of measles?
Red skin rash
138
What does tobacco mosaic virus (TMV) do and how is it spread?
- Discolours leaves and destroys cells, preventing photosynthesis.
- Spread by contact between diseased and healthy plants and by animal vectors.
139
What type of pathogen is salmonella?
Bacteria
140
Where can salmonella be found?
Raw meat, poultry, eggs and egg products.
141
What are some symptoms of salmonella food poisoning?
- Fever
- Abdominal cramps
- Vomiting
- Diarrhoea
142
What type of pathogen is rose black spot?
Fungi
143
What is a symptom of rose black spot?
Purple or black spots on leaves.
144
What type of pathogen is malaria?
Protist
145
What are the 4 main components of the body which defend us from pathogens?
- The skin
- The respiratory system
- The stomach
- White blood cells
146
How does the skin protect us from pathogens?
- Acts as a barrier by covering tissues underneath.
- Produces antimicrobial secretions to kill pathogenic bacteria.
- Heals quickly when cut using blood clots.
147
How does the respiratory system protect us from pathogens?
- Hair and mucus in the nose trap pathogens and dirt particles.
- Trachea and bronchioles secrete mucus to trap pathogens.
- Cilia beat to waft the mucus back up to the throat where it is swallowed.
148
How does the stomach protect us from pathogens?
- Produces acid which kills pathogens in the mucus you swallowed and in the food you eat.
149
How do white blood cells protect us from pathogens?
- Ingesting pathogens (phagocytosis)
- Producing antibodies
- Producing antitoxins
150
How do aphids harm plants and how can they be stopped?
Aphids use their sharp mouths to feed on sugar-rich sap in the phloem, taking the plants nutrients and weakening it.
They can be stopped using chemical pesticides or biological pest control such as ladybirds to eat aphids and their larvae.
151
What are the 2 main mineral deficiencies in plants, why are they needed, and happens when not provided?
**Nitrate:** Converts sugars to protein. Plant will not grow properly when not provided. (Stunted growth.)
**Magnesium:** Used to make chlorophyll. Plant's leaves will turn yellow when not provided (chlorosis), so less photosynthesis and less growth.
152
What are the physical barriers of a plant and what do they do?
**Cellulose cell walls:** strengthens the plant to resist invasions.
**Tough waxy cuticle:** barrier to pathogen entry.
**Bark on trees:** it is a layer of dead cells on the outside of stems for a protective layer.
153
What are the chemical barriers of a plant and what do they do?
**Antibacterial chemicals:** protects plants against pathogens.
**Poisons:** deters herbivores.
154
What adaptations do plants have to avoid being eaten?
- Poisons
- Thorns
- Hairy stems / leaves
- Dropping or curling when touched
- Mimicry
155
What is a vaccine and what do they do?
A dead or inactive form of a pathogen. They are injected into the body and white blood cells produce antibodies for it as if it was the active form. The white blood cells can now produce antibodies much faster.
156
What is herd immunity?
When not all, but most of a society is vaccinated against a pathogen.
157
Why are treatments for viruses difficult?
They live inside cells, so treatment on the viruses could damage cells.
158
What antibody did Alexander Fleming discover?
Penicillin from the mould *Penicillium*
159
What drugs can be extracted from foxglove plants?
Digitalis and digoxin.
160
Where does aspirin come from?
Willow tree bark
161
What is preclinical testing?
Tests for drugs carried out in laboratories on cells, tissues or organs and then tested on animals.
162
What are clinical trials?
Drug testing on healthy volunteers and then patients.
163
What is placebo?
An inactive substance used to represent a drug to use as a control.
164
What are the basic steps to making monoclonal antibodies?
1) Combine mouse lymphocyte with a tumour cell to make a hybridoma.
2) Hybridoma cells divide to make a large number of identical cells that produce the same antibodies.
3) The antibodies are collected and purified.
165
What can monoclonal antibodies be used for?
- Treating diseases
- Pregnancy tests
- Disease diagnosis
- Monitor hormone levels
- Locate specific molecules by adding fluorescent markers to a monoclonal antibody
166
What are the advantages and disadvantages of monoclonal antibodies?
**Advantages**
- Target diseased cells without harming healthy cells.
**Disadvantages**
- Side effects
- Expensive
167
What can monoclonal antibodies do against diseases?
- Target specific antigens on certain cancer cells.
- Carry radioacive substances, toxic drugs or another chemical directly to cancer cells without damaging other cells.
- Trigger the immune system to recognise and destroy cancer cells.
- Block receptors on the surface of cancer cells to stop them from dividing.
168
What is a causal mechanism?
When 2 factors have a consistent correlation.
169
What factors could increase chance of diseases?
- Age
- Genetics
- Lifestyle (like diet, activities and inhaling carcinogens)
- Envirionmental factors
170
What is a tumour?
A mass of abnormally growing cells.
171
What is a:
1) Benign tumour
2) Malignant tumour
**Benign**
A tumour that grows in one place. Doesn't invade other tissues but can be dangerous if it grows in tissues like the brain.
**Malignant**
A tumour which can spread to healthy tissues through the bloodstream, causing secondary tumours.
171
What can cause cancer?
- Genetics
- Carciogens (smoking)
- Ionising radiation
- Virus infections
172
What 2 methods can treat cancer?
- Radiotherapy
- Chemotherapy
173
What does tobacco smoke contain?
- Nicotine (addictive substance)
- Carbon monoxide (toxic gas)
- Tar (Sticky black substance which accumulates in lungs and is a carcinogen.)
- Chemicals that anaesthetise the cilia
174
What are the problems caused by smoking?
- Carbon monoxide carried instead of oxygen in the blood.
- A pregnant woman's baby will receive less oxygen.
- Mucus containing dirt and pathogens build up in airways.
- Tar and other chemicals inflame the bronchi (causing bronchitis.)
- Tar can damage the alveoli.
- Tar causes cancers in the resiparatory system.
- Cardiovascular disease.
175
What can obesity lead to?
- Type 2 diabetes
- High blood pressure
- Heart disease
176
How does regular exercise reduce the chance of cardiovascular disease?
- Lowers blood choleterol levels.
- Reduces fatty deposits in the blood vessels.
- Building muscle tissue, increasing metabolic rate.
- Improving blood supply to heart.
177
What part of a cell absorbs sunlight for photosynthesis?
Chloroplasts (Chlorophyll)
178
What is the word equation for photosynthesis?
Carbon dioxide + Water
----> Glucose + Oxygen
| (The arrow is also light energy.)
179
What is some glucose converted into and why?
Into glycogen for storage
180
How are leaves adapted for photosynthesis?
- Broad and flat leaves for large surface area.
- Thin so the diffusion path is short.
- Photosynthetic leaves contain chlorophyll.
- Veins contain xylem, bringing water.
- Veins contain phloem, taking glucose away.
181
How might the rate of photosynthesis be slowed down?
- Lack of light
- Too cold (enzymes won't work efficiently)
- Not enough carbon dioxide
182
What are the uses of glucose?
- Converted into glycogen for storage in animals
- Converted into starch for storage in plants
- Respiration
- Conversion into fats and oil for storage
- Produces cell walls to strengthen cell walls
- Produce amino acids
183
What type of reaction is aerobic respiration?
Exothermic
| (Glucose and oxygen transfer energy)
184
What is the word equation for aerobic respiration?
Glucose + Oxygen
----> Carbon dioxide + Water
185
What might energy be used for in an organism?
- Build larger molecules from smaller ones
- Muscle contraction
- Maintaining constant body temperature
- Move materials such as mineral ions with active transport
- Building sugars, nitrates and other nutrients inot amino acids and then proteins in plants.
186
How does the body respond when exercising?
- Increased heart rate
- Blood vessels supplying the muscles dilate (widen)
- Rate of breathing and depth of breathing increase.
187
What do muscles store glucose as?
Glycogen
188
What is anaerobic respiration?
When glucose is not completely broken down and lactic acid is produced. This happens when there is a lack of oxygen.
189
How is lactic acid removed from muscles?
Lactic acid in muscles are transported to the liver via the bloodstream and then converted back to glucose
190
What do plants produce when respiring anaerobically?
Ethanol and carbon dioxide
191
What is anaerobic respiration in yeast cells called?
Fermentation
192
What are the roles of the liver?
- Turning excess amino acids into ammonia through deamination.
- Poisonous substances are detoxified.
- Old red blood cells are broken down into iron to make new red blood cells.
- Lactic acid is transported to the liver through the blood and converted into glucose.
- Excess glucose is stored as glycogen in the liver.
193
What is homeostasis?
When your body maintains a constant internal environment.
194
What internal conditions are maintained in homeostasis?
- Body temperature
- Water content
- Blood glucose concentration
195
What are effectors?
Muscles or glands which bring about a response to a stimulus.
196
How is information passed through nerve cells?
Electrical impulses through neurones
197
What does the central nervous system compose of?
- Brain
- Spinal cord
198
What is the difference between sensory neurones and motor neurones?
Sensory neurones carry electrical impulses to the CNS, motor neurons carry electrical impulses away from the CNS.
199
What is the full route through the nervous system?
stimulus --> receptor --> sensory neurone --> CNS --> motor neurone --> effector --> response
200
What is the difference between a reflex action and a normal reaction?
Reflex actions are sub-conscious and go through the spinal cord.
Normal reactions are conscious and go through the brain.
201
How are messages sent across the spinal cord?
Electrical impulses from the sensory neurone are neurotransmitted across a synapse and gets turned into a chemical impulse to go through the relay neurone. The chemical impulse then gets neurotransmitted across another synapse and gets turned into an electrical impulse and moves down the motor neurone.
202
What does the cerebal cortex do?
Concerned with consciousness, intelligence, memory and language.
203
What does the cerebellum do?
Concerned with coordination of muscular activity.
204
What does the medulla do?
Concerned with unconscious activities, like heartbeat and breathing.
205
What does the pituitary gland do?
Acts as a master gland, produces many hormones.
206
What does the hypothalamus do?
Helps maintain the body temperature using the thermoregulatory centre.
207
How do scientists study the brain?
- Studying patients with brain damage.
- Electrically stimulating parts of the brain.
- MRI scans.
208
What are some problems with treating the brain?
- Drugs do not always pass through the membranes surrounding the brain.
- The function of each area of the brain is not fully understood.
209
How do muscles in the iris adapt to different light levels?
**Dim Light**
Circular muscles slacken. Radial muscles pulled tight. Pupil dilates.
**Bright Light**
Circular muscles pulled tight. Radial muscles slacken. Pupil constricts.
210
How do muscles in the lens adapt to objects at different distances?
**Near Objects**
Suspensory ligament relaxes. Ciliary muscle contracts. Lens becomes short and fat.
**Distant objects**
Suspensory ligament pulled tight. Ciliary muscle relaxes. Lens becomes long and thin.
211
Where should light ideally be focused onto in the eye?
The retina
212
How are messages from the eye sent to the brain?
When light hits the retina, light sensitive cells are stimulated. They send impulses to the brain through sensory neurones in the optic nerve.
213
What is accomodation?
The process of changing the shape of the lens to focus on near and distant objects.
214
What is:
1) Myopia
2) Hyperopia
1) Short-sightedness
2) Long-sightedness
215
How can bad eyesight be rectified?
- Glasses
- Contact lenses
- Laser eye surgery
- Lens replacement
216
What is the endocrine system?
A system made of glands that secrete hormones into the bloodstream.
217
What is the male and female sex hormone?
- Male: Testosterone
- Female: Oestrogen
218
Where is insulin produced, when is it produced and what does it do?
- Produced in the pancreas.
- Produced when there is excess glucose in blood.
- Causes glucose to convert into glycogen and move from bloodstream to cells.
219
What is glucose stored as in:
1) Animals
2) Plants
**Animals:** As glycogen in the liver and muscles.
But when these stores are full, glucose is stored as lipids which can make a person obese.
**Plants:** As starch
220
Where is glucagon produced, when is it produced and what does it do?
Produced in the pancreas.
Produced when there is too little glucose in the blood.
Causes glycogen in the liver to be changed back to glucose and released back into the blood.
221
What is the difference between type 1 diabetes and type 2 diabetes?
**Type 1 Diabetes**
This type is genetic. It happens when the pancreas produces too little or no insulin. Blood glucose level will be very high.
**Type 2 Diabetes**
This type is not genetic. It happens when the body does not respond to its own insulin. One significant factor is obesity.
222
How can type 1 diabetes be treated?
- Insulin injections
- Pancreas transplants
- Using embryonic stem cells to produce insulin producing cells.
- Genetically engineering the pancreas.
223
How can type 2 diabetes be controlled?
- Diet
- Exercise
- Reducing carbohydrate intake
- Drugs prescribed by doctors
224
What is a negative feedback loop?
A process where a effector causes an opposite output in order to maintain the ideal level of what is being regulated.
225
What is thyroxine?
- Hormone produced by thyroid gland in neck.
- Controls metabolic rate
- Controls how much oxygen is used by tissues
- Controls how the brain of a growing child develops.
- Important in growth and development.
226
What is adrenaline?
- Hormone produced by adrenal gland above kidneys.
- Released when stressed, frightened or angry for preparation for a response.
- Causes a 'fight or flight' reaction.
227
What does adrenaline do to the body?
- Increased heart rate
- Increased breathing rate
- Glycogen in liver converted to glucose to respire
- Pupils dilate to let in more light
- Mental awareness increases
- Increased flow in blood containing extra glucose and oxygen to limb muscles
228
What are primary sexual characteristics?
Sexual organs which babies are born with.
229
What are secondary sexual characteristics?
Sexual organs which develop during puberty.
230
How does a female's body change during puberty?
| (Name as many as you can)
- Growth spurt
- Underarm and pubic hair
- Breast development
- External genitals grow
- Body fat is deposited in hips and upper thighs
- Brain matures
- Mature ova form at the start of every month
- Uterus grows and becomes active
- Menstruation begins
231
How does a male's body change during puberty?
| (Name as many as you can)
- Growth spurt
- Underarm, pubic and facial hair
- Larynx gets bigger and voice breaks
- External genitals grow
- Testes grow and produce sperm
- Shoulders and chest broaden
- Muscles develop
- Brain matures
232
What are the 4 hormones involved in the menstrual cycle?
- FSH (Follicle Stimulating Hormone)
- LH (Luteinising Hormone)
- Oestrogen
- Progesterone
233
Where is FSH secreted, and what does it do?
- Secreted by pituitary gland
- Matures eggs in ovaries
- Stimulates ovaries to produce oestrogen
234
Where is oestrogen secreted and what does it do?
- Secreted by ovaries
- Stimulates lining of uterus to grow after menstruation in preparation for pregnancy
- Inhibits production of FSH and stimulates LH production when oestrogen levels are high
235
Where is LH secreted and what does it do?
- Secreted by pituitary gland
- Stimulates the release of mature egg from ovary
- Levels of LH fall when ovulation has taken place
236
Where is progesterone secreted and what does it do?
- Secreted by empty egg follicle in ovary after ovulation
- Maintains uterus lining
- Inhibits FSH and LH production
- Helps maintain pregnancy if egg is fertilised
237
What is contraception?
Stopping sperm cells from reaching the egg cell or prevent a fertilised egg from implanting in the uterus to prevent pregnancy.
238
What are some contraception methods?
| (Name as many as you can)
- Oral contraceptive pill
- Injections
- Patches
- Spermicide
- Condom
- Diaphragm / cap
- Intrauterine device
- Abstinence
- Male sterlisation
- Female sterilisation
239
What are some potential causes of infertility?
- Lack of hormones
- Damage to oviducts
- Obesity
- Eating disorders
- Age
240
How can women with insufficient hormones become fertile again?
Artificial FSH to mature the egg and artificial LH to trigger ovulation.
241
What does IVF stand for and what are the stages involved in it?
**In Vitro Fertilisation**
1) Giving a mother FSH to stimulate the maturation of several eggs
2) Giving a mother LH to stimulate the ovaries to the point of ovulation
3) Eggs are collected from the mother and fertilised by sperm from the father in a laboratory.
4) The fertilised eggs develop into embryos in special solutions.
5) When the eggs are tiny balls of cells, the embryos are inspected using a microscope and the healthy ones are chosen.
6) One or two of the healthy embryos are inserted into the mother's uterus.
242
What is the main advantage of IVF?
Infertile women can have the chance of having a baby.
243
What are some disadvantages of IVF?
- Expensive for NHS and individuals
- Requires a lot of skill to carry out
- Can result in multiple births, premature births, miscarriage and stillbirths
- Not always successful, which is emotionally and physically stressful.
- Ethical issues if the mature eggs or embryos of a woman are stored for future use.
244
What are plant responses called?
Tropisms
245
What is phototropism?
When plant shoots grow towards light.
246
What is gravitropism?
When roots grow down towards gravity.
247
Which hormone controls phototropism and gravitropism?
Auxin
248
How does auxin distribute throughout the shoot in different light conditions and what does this mean for the shoot's growth?
If light is equal all around the shoot, auxin distributes evenly, and the shoot will grow straight up.
If light falls on one side of the shoot, auxin diffuses away from the light. This causes the cells away from the light to grow more, which makes the shoot bend towards the light.
249
How does auxin distribute throughout the root and what does this mean for the root's growth?
Auxin in the root diffuses downwards, the direction of gravity, and this will slow down the growth of the side of the root with auxin. This will cause the other side to grow more, making the root bend downwards.
250
What do gibberellins do to plants?
- End seed dormancy.
- Speed up germination of barley seeds to make malt.
- Promote flowering throughout the year.
- Increase the size of fruits.
251
What does ethene do to plants?
Speeds up the ripening of fruits.
252
What does the thermoregulatory centre do?
Contains receptors that detect the temperature of the blood flowing through the brain. It sends impulses to the brain about skin temperature.
253
How would the body respond to a high body temperature?
- Vasodilation
- Sweating
- Hairs lie flat
254
How would the body respond to a low body temperature?
- Vasoconstriction
- Shivering
- Hairs pulled up erect
255
What is vasodilation and vasoconstriction?
**Vasodilation**
Blood vessels near the skin dilate, allowing more blood to flow there. Energy is transferred out by radiation into the environment and the skin cools.
**Vasoconstriction**
Blood vessels near the skin constrict, allowing less blood to flow there. Less energy is radiated into the environment.
256
Where and how is urea produced?
Produced in the liver through the breakdown of amino acids.
257
What do the kidneys do?
Controls the amount of water, mineral ions and urea that the body excretes using selective reabsorption
258
Which hormone controls water reabsorption in the kidneys?
ADH
259
What does ADH do?
A hormone that controls the amount of water that the kidney reaborbs
260
What is kidney dialysis?
A machine that carries out the same job as the kidneys by passing the blood between a partially permeable membrane surrounded by dialysis fluid.
261
What does dialysis fluid contain and how much of each?
- **Glucose:** same concentration as blood
- **Mineral ions:** same concentration as blood
- **Urea:** lower concentration than blood
262
What are the advantages and disadvantages of kidney transplants?
**Advantages**
- Longer lifespan than dialysis
- Patients won't have to undergo regular dialysis
- Cheaper than dialysis
**Disadvantages**
- Infection risk
- Rejection risk
- Finding a donor can take a while
- Kidney lasts 8-9 years on average
- Patient must take immunosuppressant drugs to avoid rejection, but increase risk of infection.
263
What are the similarities and differences between sexual and asexual reproduction?
**Similarities**
- Both create new organisms
**Differences**
- Sexual reproduction involves the fusion of 2 gametes (sperm and egg) from 2 parents. Asexual reproduction involves a single organism/cell.
- Sexual reproduction has variation in offspring. Asexual reproduction produces genetically identical offspring
- Sexual reproduction takes longer, as a mate needs to be found and due to the process of mating. Asexual reproduction is faster as it doesn't involve a mate
264
What is meiosis?
A form of cell division which produces 4 non-identical, haploid sex cells or gametes
265
What are the sex cells in:
1) Animals
2) Plants
**Animals:** egg cells and sperm cells
**Plants:** egg cells and pollen
266
How many times do cells divide in:
1) Mitosis
2) Meiosis
**Mitosis:** once
**Meiosis:** twice
267
What is a zygote?
The first cell of a new organism when an egg cell and sperm cell fuse during fertilization
268
What are the advantages and disadvantages of asexual reproduction?
**Advantages**
- Only 1 parent needed
- Quicker than sexual reproduction
- Less energy required
- Many identical offspring are created, ideal in favourable conditions
**Disadvantages**
- Offspring have little variation
- Environmental change affect all offspring
269
What are the advantages and disadvantages of sexual reproduction?
**Advantages**
- Produces variation, allowing natural selection
- Natural selection can be sped up by humans in selective breeding to increase food production
**Disadvantages**
- Two gametes are needed, usually requiring 2 parents
- Takes time and energy to find a mate or spread gametes
- Slower than asexual reproduction
270
How do malarial parasites reproduce:
1) In mosquitoes
2) In humans
**Mosquito:** sexually
**Human:** asexually
271
What is a gene?
A small section of DNA on a chromosome
272
What is the genome of an organism?
The entire genetic material of an organism
273
How does understanding the human genome help us?
- We can search for genes linked to different diseases
- We can understand and treat inherited disorders
- We can trace human migration patterns from the past
274
What are the 4 bases in DNA and how are they linked together?
A, C, G and T
**A** and **T** link
**C** and **G** link
275
What is a nucleotide?
A unit containing a sugar, a phosphate and a base.
276
What does **amylase** catalyse, where is it produced and where is it used?
- Catalyses digestion of starch into sugars
- Produced in salivary glands, pancreas and small intestine
- Used in mouth and small intestine
277
What does **protease** catalyse, where is it produced and where is it used?
- Catalyses break down proteins into amino acids
- Produced by stomach, pancreas and small intestine.
- Used in stomach and small intestine
278
What does **lipase** catalyse, where is it produced and where is it used?
- Catalyses breakdown of lipids into fatty acids and glycerol
- Produced in pancreas and small intestine
- Used in small intestine
279
What are the 2 stages in protein synthesis?
- Transcription
- Translation
280
What is natural selection?
A process where organisms that are better adapted to the environment will survive and reproduce
281
What is selective breeding?
An artificial process where humans choose organisms with desired characteristics to breed, resulting in offspring having those traits
282
What is a community?
A group of different species that live in the same general area
283
What is a population?
All members of a single species that live in a habitat
284
What is an ecosystem?
The interaction of a community of biotic and abiotic factors elements of their environment
285
What is intraspecific competition?
When organisms of the same species compete with each other for resources
286
What is interspecific competition?
When organisms of different species compete against each other for resources
287
What do animals compete for?
- Food
- Water
- Mates
- Space
- Breeding sites
288
What do plants compete for?
- Light
- Water
- Minerals
- Space
289
What are some biotic factors?
| (Name as many as you can)
- Availability of food
- Number of predators and prey
- New pathogens or parasites
- New competitors
290
What are some abiotic factors?
| (Name as many as you can)
- Availability of water
- Availability of mineral ions
- Wind intensity and direction
- Availability of carbon dioxide
- Availability of oxygen
- Availability of habitats
- pH of soil
- Amount of light
- Temperature
291
What is an extremophile?
Organisms, usually microorganisms, that are adapted to live in conditions where most enzymes don't work becuase they denature
| (i.e. organisms that live in extreme conditions)
292
How are animals in colder environments adapted?
- Thick fur
- Blubber
- White camouflage for snow
- Small surface area : volume ratio
293
How are animals in hotter environments adapted?
- Nocturnal behaviour
- Yellow-brown fur for camoflague on sand
- Water conservation
- Large surface area : volume ratio
294
What is biomass?
Dry mass of material within a living organism
295
What is a producer?
An organism that makes its own food, usually through photosynthesis. They are always at the start of a food chain.
296
What is a consumer?
An organism that cannot make its own food so must eat other plants and/or animals for energy
297
What is a decomposer?
Bacteria or fungi that break down dead plant and animal matter
298
Which process is the only process that removes carbon dioxide from the atmosphere?
Photosynthesis
299
Which organisms respire?
All organisms
300
Which factors affect rate of decay by decomposers?
- Temperature
- Humidity
- Oxygen availability
301
What is biodiversity?
The variety of living things and their interactions in a given area
302
What are the steps involved in water becoming polluted?
- Fertilisers and untreated sewage spills in water, causing high levels of nitrate ions
- High levels of nitrate ions causes algae and other water plants to rapidly grow
- Competition for light increases and many plants die because they cannot photosynthesise
- Microorganisms feed on dead plants so the microorganism population increases rapidly
- Respiration by microorganisms depletes oxygen concentration in water
- Aerobic organisms like fish die due to lack of oxygen, leading to even more decay
- Lack of oxygen eventually means the water cannot sustain living organisms
303
Why do humans carry out large-scale deforestation?
- Timber
- Land for agriculture
- Buildings
- Mining
304
What are the consequences of large-scale deforestation?
- Destruction of habitats, reducing biodiversity
- Climate change due to carbon dioxide store being released, and less photosynthesis
305
Why do humans destroy peat bogs?
- Farming
- Fuel
- Compost
306
How are humans working to maintain biodiversity?
- Breeding programmes
- Protection / regeneration of habitats
- Reintroduction of field margins and hedgerows
307
What is food security?
Having enough available, affordable, nutritious food to feed a population
308
Which factors affect food security?
- Environmental changes
- Pests / pathogens
- Changing diets
- Increasing birth rates
- Cost of agricultural inputs
- Conflicts / war
309
Why isn't all biomass transferred to the next trophic level?
- Not all of previous level is eaten
- Not all biomass is fully digested
- Excess protein is broken down into urea
- Some biomass is used for respiration
- Some biomass is used for movement
- Some biomass is used for thermoregulation
310
How are animals managed so food production is more efficient?
- Limiting movement
- Controlling temperature
311
How are fish stocks being maintained?
- Limits on how much fishing can occur
- Large nets so small fish can escape
- Smaller fishing vessels
312
What is Fusarium?
A fungus that is grown to produce mycoprotein, a protein-rich food supplement for vegetarians
313
What are the advantages of using mycoproteins instead of meat?
- Fungi use cheap food
- Fungi reproduce rapidly
- Suitable for vegetarians
- No need to farm and slaughter animals
- Low in fat
314
What is aseptic technique?
A set of practices used to prevent contamination when working with microorganisms
315
How often do bacteria multiply?
Around every 20 minutes
316
How should you decontaminate before a bacterial growth practical?
- Wipe down surfaces
- Use clean pipettes
- Rinse glassware beforehand
- Inoculating loop through a flame
- Wash hands
317
What are the stages involved during **transcription** in protein synthesis?
**1)** DNA unwinds and 2 strands seperate
**2)** Nucleotides in the nucleus line up next to a strand, using complementary base pairings
**3)** The nucleotide and strand are bonded together, forming a template molecule
**4)** The template molecule detaches and leaves the nucleus
**5)** The 2 DNA strands come back together and the double-helix winds back up
318
What are the stages involved during **translation** in protein synthesis?
**1)** Template molecules attaches to a ribosome
**2)** A carrier molecule binds to the template using complementary base pairing to attach to the first triplet
**3)** The next carrier arrives, with a complementary base sequence to the next triplet
**4)** A bond is formed between the 2 amino acids
**5)** The first carrier leaves and a third carrier binds to the third triplet
*This continues until all amino acids are in place*
319
What is the inverse square law?
**Light intensity = 1 / distance²**
Intensity of light is inversely proportional to the square of the distance from the light source
| (This is important for the photosynthesis required practical)
320
What are the levels of organisation? Order from smallest to largest
- Cells
- Tissues
- Organs
- Organ systems
- Organisms
321
What does the gall bladder do?
Stores and releases bile
322
What are new drugs trailled for?
- **Toxicity:** are they harmful?
- **Efficacy:** does it work?
- **Dose:** what amount is safe and effective?
323
How does a healthy kidney produce urine?
- Filtering blood
- Reabsorbing **all** glucose
- Reabsorbing mineral ions the **body needs**
- Reabsorbing water the **body needs**
- Releasing urea, excess mineral ions and water in the urine
324
What is a mutation?
A change in a gene or chromosome
325
What are alleles?
Different forms of a gene
326
What is a phenotype?
The physical appearance of a characteristic
327
What is a genotype?
The genetic makeup of an organism
328
What does homozygous mean?
Both alleles being the same
329
What does heterozygous mean?
2 different alleles
330
How can dominant and recessive alleles be expressed?
- **Dominant alleles** can be expressed if one or both alleles are dominant
- **Recessive alleles** can be expressed only if both alleles are recessive
331
What is polydactyly and what type of allele is it?
**Dominant allele**
- Genetic condition when a baby is born with extra fingers or toes
332
What is cystic fibrosis and what type of allele is it?
**Recessive allele**
- Causes production of thick, sticky mucus which can affect several organs
333
What is a carrier?
An organism which has a recessive allele which isn't expressed
334
What can family trees be used for?
- Tracking inherited diseases
- Showing family likenesses
- Showing different alleles that organisms inherited
335
What are the methods for screening embryos?
- Aminocentesis
- Chronic Villus Sampling (CVS)
- Screening IVF Embryos
336
What is aminocentesis?
Taking fluid around the developing embryo at around 15-16 weeks of pregnancy. Fluid contains fetal cells which can be used for genetic screening.
337
What is chorionic villus sampling?
Taking a small sample of tissue from the developing placenta at around 10-12 weeks of pregnancy. This provides fetal cells for genetic screening.
338
What is screening IVF embryos?
Embryos produced through IVF are tested before being implanted in the mother
339
What are the concerns about embryo screening?
- Risk of miscarriage
- Unreliable info from the screening process
- Decisions about terminating a pregnancy are hard do take
- Screening is expensive
- Unethical to destroy embryos
340
Why might characteristics of individuals of the same kind vary?
- Different inherited genes
- Different environments for development
- Combination of both
341
What is evolution?
The change in frequency of an allele in a population over time
342
What is selection pressure?
When a particular mutation provides a survival advantage
343
What is natural selection?
When organisms with advantageous alleles can survive and reproduce easier. This increases the frequency of the advantageous alleles in future generations.
344
What is selective breeding?
When people select animals or plants with desired characteristics to breed together to create offspring with the desired traits
345
What are the disadvantages of selective breeding?
- Less variation in the population
- New disease or climate change could destory the whole population
- Inbreeding of related organisms
346
What is a clone?
An organism which is genetically identical to its parent
347
What is genetic engineering?
Modifying the genetic material of an organism
348
What are the steps involved in genetic engineering?
- Gene for desired characteristic is cut out of a chromosome
- Gene is inserted into a vector to transfer the gene
- The vector inserts the gene into the required cells in the early stages of life, so the desired characteristic can develop
349
What are the types of cloning?
- Cuttings (plant)
- Tissue culture (plant)
- Embryo splitting / artificial twinning
- Adult cell cloning
350
What is cloning with cuttings?
Taking parts of a plant and growing it seperately using plant hormones
351
What is cloning with tissue culture?
Taking small groups of cells from part of a plant and growing them under special conditions
352
What are the steps involved in embryo splitting / artificial twinning?
- Divide embryo into individual cells
- Each cells grows into an identical emybro in a lab
- Transfer embryos into host mothers, which have hormones to get them ready for pregnancy
- Identical cloned calves are born
353
What are the steps involved in adult cell cloning?
- Nucleus from adult cell and an empty egg from 2 different organisms are fused using a mild electric shock
- This will divide to form an embryo
- Cloned embryo is implanted into uterus of another organism
- Offspring is born which is a clone of the organism from which the nucleus of an adult cell was taken
354
What are the advantages and disadvantages of cloning?
**Advantages**
- Allows genetic engineering
- Can save animals from extinction
**Disadvantages**
- Concerns about ethics of cloning
- Cloning limits variation
- Concerns about cloning humans
355
What did Gregor Mendel do?
Carried out breeding experiments on pea plants. He noticed clear patterns of inheritance and realised some characteristics were dominant and some were recessive.
| (This was before chromosomes were discovered)
356
What was Jean-Baptiste Lamarck's theory of evolution?
**Inheritance of acquired characteristics**
A theory where characteristics which were used by organisms would grow and develop. These characteristics would be passed from parents to offspring. If the characteristic wasn't used, it would shrink and not be passed on.
357
What was Charles Darwin's theory of evolution?
**Natural selection**
He noticed organisms of a particular species show variation for a characteristic. He concluded that animals which are best suited to the environment are more likely to survive and reproduce
358
Why did people initially object Charles Darwin's theory of natural selection?
- The theory challenged the idea of God
- Insufficient evidence
- Darwin couldn't explain why there was variation
359
What was Alfred Russel Wallace's theory of evolution?
**Theory of speciation**
New species can arise if a group becomes isolated from the rest. Different environments could lead to different selection pressures.
360
What is a species?
A group of organisms with similar characteristics that can breed successfully to produce fertile offspring
361
What is a fossil?
Remains of organisms from millions of years ago, usually preserved in rocks and ice
362
How can fossils be formed?
- Hard parts like bones and shells don't decay easily
- Conditions for decay not met
- Mineralisation
- Preserved traces such as footprints
363
What is mineralisation?
When parts of organisms are replaced by minerals as they decay
364
Why is the fossil record incomplete?
- Soft bodied organisms have little fossil traces
- Most organisms didn't fossilise
- Many fossils are yet to be found
- Geological activity destroyed many fossils
- Fossils give us evidence about organisms from millions of years ago
365
What could a complete fossil record potentially tell us?
- Complete record of evolution
- What the climate was like millions of years ago
- That many organisms didn't adapt much as their ancestors were already well adapted
366
Why are ice fossils valuable?
- Organisms are often intact, giving a clear insight into what they looked like
- Very rare and often thousands of years old
- Can show what an animal was eating
- DNA can be extracted and compared to DNA of modern organisms
367
What is extinction?
When a species that once existed completely dies out
368
What factors can cause extinction?
- New disease
- New predators
- Competition
- Environmental changes
- A catastrophic event
369
What is a mass extinction?
When many or even most species die out, usually over a short period of time
370
What are the consequences of mass extinction?
- Loss of biodiversity
- Decrease in range of alleles
- Evolution of new species
371
How do antibiotic-resistant bacteria arise?
- Majority of bacteria in a colony killed by an antibiotic
- Some survive through mutation, and reproduce to form a resistant colony
- A new antibiotic is used on the new colony, where the majority are killed
- Some survive through mutation, and reproduce to form a resistant colony
- Process repeats
372
How can we slow down the rate of development of antibiotic-resistant bacteria?
- Not overusing antibiotics
- Making sure patients finish their course of medicine
- Restrict agricultural use of antibioitcs
- Washing hands
- Isolating those who are infected with antibiotic-resistant bacteria
373
What is MRSA?
A bacteria which has evolved to be resistant to commonly used antibiotics
374
What is classification?
Organisation of different organisms into groups based on their similarities
375
What did Carl Linnaeus do?
Came up with the system used for classification
376
What is the order of classification?
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
377
How are animals named binomially?
An organism's genus name followed by their species name
378
What did Carl Woese do?
Introduced a higher level of classification called a domain
379
What are the three domains?
- Archea
- Bacteria
- Eukaryota
380
What are archea?
Primitive forms of bacteria which can survive in extreme condtions. Contains one kingdom, archaebacteria.
381
What are bacteria?
| (Domain)
True bacteria and cyanobacteria, which are bacteria-like organisms which can photosynthesise. Contains one kingdom, eubacteria.
382
What are eukaryota?
Organisms where all cells contain a nucleus with genetic material. Contains four kingdoms, protista, fungi, plants and animals.
383
Which sex chromosomes are found in the body cells of a female?
**XX**
384
Which sex chromosomes are found in the body cells of a male?
**XY**
