4.4.5Genetics, Variation and Interdependence

Environmental Adaption — AQA A Level Biology 7402 Revision Notes & Topical Questions

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4.4.5 Environmental Adaption — AQA A Level Biology 7402 notes: Describe and explain behavioural, physiological and anatomical adaptations to the environment, and relate them to natural selection.An adaptation is a characteristic that increases an organism's chance of survival and…

Anatomical (structural)
Exam-style question 1
Exam-style question 2
Exam-style question 3
Physiological adaptation
Behavioural adaptation

Section 1 of 9What is an adaptation?

An adaptation is a characteristic that increases an organism's chance of survival and reproduction in its environment.

What is an adaptation?

Adaptations arise by natural selection over many generations: individuals with advantageous alleles survive and breed more than others,

so the alleles spread.

It is important to note that individuals do not adapt during their lifetime to produce inherited changes, and the process is not goal-directed.

There are three categories.

Anatomical (structural)

Anatomical (structural) physical features of the body.

Physiological

Physiological processes inside the body, such as the biochemistry of cells.

Behavioural

Behavioural ways the organism acts that improve survival.

Section 2 of 9Anatomical adaptations

Anatomical adaptations include body shape, covering and the structure of organs.

In a desert, the kangaroo rat has small, concentrated urine and long nasal passages to reduce water loss.

Marram grass has rolled leaves with sunken stomata to reduce transpiration.

Arctic mammals such as the polar bear have a thick layer of fat and dense fur for insulation, small ears and a compact body,

which reduces the surface area to volume ratio and so heat loss.
- (Bergmann's rule and Allen's rule)

The opposite is seen in hot climates, where large ears (for example in the fennec fox) increase the surface area for heat loss.

The shape of a fish, streamlined for swimming, and the camouflage of a stick insect are further examples.

Section 3 of 9Physiological adaptations

These adaptations involve metabolism and internal regulation. Examples include:

the production of antifreeze proteins in fish blood, which prevent ice crystals from forming in polar waters;

the ability of the desert camel to tolerate dehydration and a large variation in body temperature without sweating;

the production of antibodies by the immune system;

the toxins produced by some snakes and plants;

haemoglobin with a higher affinity for oxygen in organisms that live at altitude or deep in water, such as the llama or the seal's myoglobin;

hibernation, where metabolic rate and body temperature fall to conserve energy in the winter.

Bacteria show physiological adaptations, such as enzyme production for breaking down a new substrate, or resistance to antibiotics.

Section 4 of 9Behavioural adaptations

Behaviour can also be inherited and subject to selection.

Behavioural adaptations

Examples include migration of birds to warmer areas in winter, burrowing and nocturnal activity of desert animals to avoid heat, basking in the sun by reptiles to raise body temperature, huddling of penguins to conserve heat, courtship displays and the playing dead response in some insects and the opossum.

Behavioural adaptations tend to be changed more quickly than anatomical ones, and may be learned as well as inherited.

Section 5 of 9Explaining adaptation and links

Exam answers should follow a pattern for explaining how an adaptation came about: (1) variation in a population owing to mutation; (2) a selection pressure, such as cold or predation; (3) individuals with the advantageous allele are more likely to survive and reproduce; (4) the allele is passed to the next generation; (5) over many generations the frequency increases. Where the question asks you to explain how a feature helps survival, give a clear link, for example 'the thick fur traps a layer of air, reducing heat loss by conduction, so less energy from respiration is needed to keep warm'.

This topic links to natural selection, to thermoregulation and homeostasis, to water balance in plants and animals, and to speciation.

Section 6 of 9Case study: adaptation of a desert plant and a mammal

To practise, take the kangaroo rat of the North American desert.

Case study: adaptation of a desert plant and a mammal

It never drinks, obtaining water from metabolic reactions, such as aerobic respiration of dry seeds.

It has long loops of Henle in its kidneys (physiological and anatomical),

so that it produces very concentrated urine, nasal passages that condense water vapour from exhaled air,
- and burrows in which it spends the day (behavioural),
- where the air is cooler and more humid.

Each feature reduces water loss, so individuals with the alleles for these features were more likely to survive in the dry environment and reproduce.

For a plant, a cactus stores water in a thick fleshy stem, has spines in place of leaves to reduce the surface area and deter herbivores, a thick waxy cuticle, and shallow widely spread roots that rapidly take up rainfall.

Case study: adaptation of a desert plant and a mammal

It opens its stomata at night and fixes the carbon dioxide into organic acids, closing them by day,

which is a physiological adaptation that minimises transpiration.

Always link each feature to its function and describe how it reduces water loss, absorbs water or uses it efficiently.

Section 7 of 9Exam-style questions

Explain how the thick fat layer of a polar bear is an adaptation to its environment. [3]3 marks
Describe how natural selection could lead to an increase in the frequency of an allele for the production of antifreeze proteins in a population of fish. [4]4 marks
Distinguish between a behavioural and a physiological adaptation, giving an example of each. [2]2 marks

Section 8 of 9Key terms

Term	Meaning
Adaptation	A feature that increases the chance of survival and reproduction.
Anatomical adaptation	A structural feature of an organism.
Physiological adaptation	A feature of the metabolism or body processes.
Behavioural adaptation	A pattern of behaviour that increases survival.
Selection pressure	An environmental factor that affects survival.
Hibernation	A state of reduced metabolism in winter.
Camouflage	Colouring or pattern that makes an organism hard to see.

Section 9 of 9Exam technique

Writing that the animal 'needs' the adaptation and so develops it.

Describing the adaptation but not explaining how it helps survival.

Confusing physiological and anatomical adaptations; structure is anatomical, biochemical processes are physiological.

Saying that acquired characteristics, such as larger muscles from exercise, are inherited.

Forgetting to link the adaptation to the selection and allele frequency.

Last updated: 14 October 2026

Section 1 of 9What is an adaptation?

Section 2 of 9Anatomical adaptations

Section 3 of 9Physiological adaptations

Section 4 of 9Behavioural adaptations

Section 5 of 9Explaining adaptation and links

Section 6 of 9Case study: adaptation of a desert plant and a mammal

Section 7 of 9Exam-style questions

Explain how the thick fat layer of a polar bear is an adaptation to its environment. [3]3 marks

Describe how natural selection could lead to an increase in the frequency of an allele for the production of antifreeze proteins in a population of fish. [4]4 marks

Distinguish between a behavioural and a physiological adaptation, giving an example of each. [2]2 marks

Section 8 of 9Key terms

Section 9 of 9Exam technique

Marked practiceQuizzes for this lesson