16.7 Adaptation in Animals

A free GCSE Biology lesson for AQA (8461) from OBA School: surviving cold and hot climates, surface area to volume ratio, and adaptations of predators and prey. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Calculate the surface area to volume ratio (SA:V) of a cube
• Explain how body size, shape, fur and fat help animals control heat loss
• Describe structural, behavioural and functional adaptations for hot, dry climates
• Explain how camouflage and other features help predators and prey

Key words

• SA:V: Surface area to volume ratio: the surface area of an object divided by its volume. Small objects have a large SA:V.
• Insulation: A layer that reduces heat transfer, e.g. fur that traps air, or fat.
• Blubber: A thick layer of fat under the skin of whales, seals and walruses.
• Camouflage: Colours or patterns that help an animal blend into its surroundings.
• Nocturnal: Active at night and resting during the day.

Surface area to volume ratio

An animal produces heat by respiration throughout its volume, but loses heat through its surface. So the ratio of surface area to volume controls how fast it loses heat.

Worked example: SA:V of cubes

2 cm cube: surface area = 6 × 2 × 2 = 24 cm²; volume = 2 × 2 × 2 = 8 cm³. SA:V = 24:8 = 3:1.
4 cm cube: surface area = 6 × 4 × 4 = 96 cm²; volume = 4 × 4 × 4 = 64 cm³. SA:V = 96:64 = 1.5:1.

Answer: the bigger cube has the smaller SA:V, so it loses heat more slowly per unit volume

Key fact: Large, compact animals (small SA:V) keep heat in. Small animals and animals with large thin ears or long limbs (large SA:V) lose heat quickly.

Living in cold climates

• Large size and compact shape with small ears and short limbs – small SA:V, so less heat is lost (e.g. polar bear, Arctic fox, walrus).
• Thick fur traps a layer of air, which is a good insulator.
• Blubber (thick fat) under the skin insulates and is also an energy store when food is scarce.
• White coat in snow gives camouflage for both hunting and hiding.
• Behaviour: migrating to warmer places or hibernating through the winter; huddling together.

Living in hot, dry climates

Desert animals must lose heat and save water.

• structural; Adaptation large thin ears; thin fur; long legs; How it helps large SA:V and good blood supply near the surface, so more heat is lost
• structural; Adaptation fat stored in one place (camel’s hump); How it helps the rest of the body has little insulating fat, so heat is lost easily
• behavioural; Adaptation nocturnal; staying in burrows by day; How it helps avoids the hottest part of the day; burrows are cool and humid
• functional; Adaptation very concentrated urine; very dry droppings; How it helps little water is lost
• functional; Adaptation sweating very little; How it helps saves water (but less cooling)

Exam tip: Always link the adaptation to heat or water: “large ears → large surface area → more heat lost to the surroundings”.

Predators and prey

Predators have adaptations to catch prey: forward-facing eyes to judge distance, sharp teeth and claws, camouflage to stalk, speed. Prey have adaptations to avoid being eaten: eyes on the sides of the head for a wide field of view, camouflage, speed, living in groups, poisons and warning colours (e.g. wasps), and spines or shells.

Common mistakes

• Saying large animals have a large SA:V. Larger animals have a smaller SA:V.
• Saying fur “keeps the cold out”. Fur traps air, which reduces heat loss from the body.
• Forgetting to cube the side for volume, or to multiply by 6 faces for surface area.
• Listing adaptations without explaining their link to heat loss, water loss or survival.

Revision questions

Try these, then check your answers below each one.

Question 1. Calculate the surface area to volume ratio of a cube with sides of 2 cm. Give the answer as n in n : 1.

Answer: 3

Working: SA = 6 × 2 × 2 = 24 cm²; V = 8 cm³; 24 : 8 = 3 : 1.

Question 2. Why do fennec foxes, which live in hot deserts, have very large ears? (Choose from: They give a large surface area for losing heat, They keep the fox warm at night, They store water, They make the fox look bigger to predators.)

Answer: They give a large surface area for losing heat

Working: Large thin ears have a large surface area with many blood vessels near the surface, so heat is lost to the surroundings.

Question 3. True or false? Small animals have a smaller surface area to volume ratio than large animals.

Answer: False

Working: False. Smaller animals have a larger SA:V, so they lose heat faster.

Related lessons

• Previous lesson: 16.6 Adapt and Survive
• Next lesson: 16.8 Adaptations in Plants
• In this chapter: 16.1 The Importance of Communities
• In this chapter: 16.2 Organisms in Their Environment
• In this chapter: 16.3 Distribution and Abundance

Continue in the full course

This lesson is section 16.7 (AGCBH1607) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.