Responses keep animals alive
Every animal, not just humans, detects stimuli and responds to them. These responses are vital for survival. By reacting quickly to changes around them, animals can find food, escape danger, keep to a comfortable temperature and find a mate to reproduce. An animal that fails to respond to danger will not survive for long.
Key idea
Responses to stimuli help animals in four main ways: escaping predators, finding food, avoiding harmful conditions, and reproducing.
Everyday examples
- Escaping predators: a deer that hears a lion runs away; a cockroach scuttles into the dark when a light is switched on.
- Finding food: a moth uses chemoreceptors to smell a flower and fly towards it.
- Avoiding harm: an earthworm moves away from bright light and dry soil to keep its skin moist.
- Reproduction: many animals respond to sound or scent signals to find a mate.
Seasonal responses
Some animals respond to changing seasons and to the time of day. Birds migrate to warmer places with more food when winter comes, and some animals hibernate, sleeping through the cold months to survive when food is scarce. Nocturnal animals such as owls become active in darkness and rest by day, avoiding the heat and their daytime enemies. All of these responses, fast or slow, increase an animal's chance of survival and of passing on its features to the next generation.
Example
When a bright torch shines on an earthworm, it quickly moves away into darker, damper soil — a response that stops its skin from drying out.