AQA GCSE Biology: Adaptations

Adaptations are the features that let organisms survive where they live. This short guide covers the three types of adaptation and the extremophiles that survive in the harshest environments. The key is to be able to sort an adaptation into the right type.

What adaptations are

Adaptations are features that enable organisms to survive in the conditions in which they normally live.

The word to be careful with is "for". An organism is not adapted in order to survive somewhere. It survives there because it happens to have features that work. The features came first, from mutation, and the environment then kept them. Writing that a cactus grew spines in order to save water has the direction backwards, and it loses the mark for the same reason as writing that an individual evolves.

The three types of adaptation

There are three kinds of adaptation.

• Structural adaptations are physical features, for example colouring for camouflage to avoid predators or to hunt prey.
• Behavioural adaptations are the ways an organism acts, for example courtship dances to attract a mate.
• Functional adaptations are biological processes, for example kidneys producing highly concentrated urine to conserve water.

Sorting an adaptation into the right type is most of what this topic is marked on, and there is a reliable test. Ask what you would need in order to see it.

• If you could point to it in a photograph, it is structural. A polar bear's blubber, a cactus's spines, a fish's gills.
• If you would need a video, it is behavioural. Birds migrating before winter, a meerkat taking its turn as lookout, a lizard moving into the sun.
• If you would have to look inside at the chemistry, it is functional. A camel producing very concentrated urine, an Arctic fish making antifreeze proteins.

The hard ones come in pairs, where the same animal gives you one of each. A camel's hump is structural, but what the hump does, storing fat that can be respired, is functional. A thick coat is structural; shivering inside it is behavioural. When a question hands you a feature, work out whether it is naming the part, the action or the process.

While you are there, the hump stores fat, not water. Respiring fat does release a little water, but a camel going without a drink survives mainly on the water it does not lose, by sweating very little and producing very concentrated urine.

Extremophiles

Extremophiles are organisms that live in very extreme environments, such as places with high pressure, high temperature or high salt concentration. An example is the bacteria that live in deep sea vents.

What makes an extremophile interesting is its enzymes. Most enzymes denature well below 50°C, so an organism living beside a vent at far above that must have enzymes whose shape holds together at those temperatures. The same applies at extreme pH or extreme salt concentration: the adaptation is happening at the level of the protein, which is why extremophiles are a functional adaptation taken to its limit.

Deep sea vents are the example worth knowing because they are extreme in two ways at once, very high temperature and very high pressure, and because the communities around them run on bacteria that take their energy from chemicals in the vent water rather than from sunlight.

How this fits together

Adapted organisms feed on one another, and these feeding relationships are shown by food chains, which are the subject of the food chains and predator-prey guide.