AQA AS Biology Unit 2 Common Questions and Answers

AQA AS Biology Unit 2 - BIOL2 The variety of living organisms

Common questions and answers from past exam papers

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  • Created on: 17-05-12 22:02
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AQA AS Biology
BIOL2 ­ The variety of living organisms
Common Exam Questions and Answers
Name the two components that make up the DNA backbone
Explain how a DNA mutation can result in a nonfunctioning enzyme
Change in the triplet code
Changes amino acid sequence (primary structure)
Change in hydrogen, ionic and disulphide bonds
Changes tertiary structure/active site shape
Substrate is not complementary/enzyme substrate complexes can not form
The Passage of Water through a Plant
Why does the rate of transpiration not equal the rate of water uptake in a plant?
Some is used in photosynthesis
Some is produced in respiration
Some is used to provide turgidity/ stored to provide support
Little amount of wind/stomata pits reduce the amount of water lost from a plants
leaves, explain why
Water vapour accumulates outside the stomata increasing humidity
This reduces the water potential gradient
Antibiotic Resistance
Suggest two ways of reducing the transmission of the bacteria MRSA
Isolation/quarantine of infected patients
Screening of patients and doctors
Sterilisation of wards and equipment
Frequent treatment with antibiotics can result in resistant strains of bacteria, explain
Mutation occurs
Producing a resistance gene
Resistant bacteria survive and reproduce
Spread resistance by vertical and horizontal gene transmission
Blood and Circulation
How does haemoglobin in red blood cells load and unload oxygen in the body?
Loading of oxygen in the lungs where partial pressure of oxygen is high so haemoglobin
becomes saturated
Unloading of oxygen in respiring tissues where partial pressure of oxygen is low
Unloading where carbon dioxide concentration is higher, pH is lower and temperature is

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AQA AS Biology
BIOL2 ­ The variety of living organisms
Compare the structural features of arteries and veins
Structural features Arteries Veins
Valves Absent Present
Relative thickness of walls Thick Thin
Elastic Tissue More Less
Smooth muscle More Less
Lumen Narrow Wide
Explain how smooth muscles in arterioles can reduce blood flow
Muscle contracts
Causing vasoconstriction (narrows lumen)
Explain how elastic tissue in the arteries even out the pressure of blood
Elastic tissue stretches when pressure is high
Elastic tissue recoils when pressure decreases to…read more

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AQA AS Biology
BIOL2 ­ The variety of living organisms
The tracheoles lead to each cell where oxygen diffuses into the cell
Ventilation by pumping of the abdomen can replenish the air in the trachea
The body is covered with a water proof waxy cuticle
Spiracles can close when the insect is inactive
Describe how single celled organisms exchange respiratory gases and explain why
this method of gas exchange is only possible in very small organisms
Diffusion through the cell surface membrane
Small organisms have…read more

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AQA AS Biology
BIOL2 ­ The variety of living organisms
Immunological evidence
Inject serum containing proteins of species A into an animal
Obtain serum containing antibodies from this animal
Add the serum containing proteins of species B into the serum containing antibodies
The amount of precipitate formed indicates the relationship
Give two reasons courtship behaviour improves the probability of successful mating
Attracts/recognises the same species
Indicates fertility
Species Diversity
What is a species?
Organisms with similar characteristics that can interbreed to produce fertile offspring
Explain…read more

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AQA AS Biology
BIOL2 ­ The variety of living organisms
Extend the line (extrapolate)
When viewing tissue cells through an optical microscope why is it important that the
sample is thin?
Need only a single layer of cells
So light can pass through
Detail is not obscured by cells underneath
How do you ensure a sample gives reliable data?
Large sample size
Chosen randomly
Why is it better to measure per gram of body mass/ percentage change/ ratios?
Allows comparison
Between animals of different masses…read more



These are brilliant,

 Thank You!

Eliza Reid

These are really useful, thank you so much!


you absolute lifesaver thank you so much


These are great, thank you!

Louisa Bourlet


Saatvik M.Reddy

this is great!

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