In order to survive, living things must be able to detect changes in their environment and react to them. This includes adapting to changing weather conditions and the threat of living things that may approach them.
Animals have up to five senses – sight, smell, hearing, taste and touch – to help them to detect changes around them. A dog may react to the smell of food by running towards it; an earthworm will react to light by burrowing underground; and a chameleon changes its skin colour and patterns to match its background. Plants don’t have senses of this kind but they can still detect changes in their environment.
Plants can react to certain changes in their environment. We have seen how plants grow towards light and water. This sunflower gradually turns as it follows the path of the Sun during the day. Some flowers, such as lilies, open during the day and close at night. Plants are remarkably sensitive to heat; light, drought, certain chemicals and gravity, but they have no special organs for detecting change.
This sea anemone reacts to touch by retracting its tentacles.
An Arctic fox’s fur turns from brown to white in winter to camouflage it in the snow.