Animals are unable make their own food so feed on plants or other animals in a food chain. They are therefore consumers. They often eat more than one kind of food so become part of more than one food chain. Some eat only plants and are called herbivores; others eat only animals and are called carnivores. Those that eat both plants and animals are called omnivores. Primary consumers are those that eat only plants (producers), secondary consumers eat primary consumers, tertiary consumers eat secondary consumers and so on. The food any particular consumer eats may fluctuate in its availability due to a variety of reasons such as:
- disease;
- competition for resources;
- climatic changes;
- human activity.
If any of these occur, then the consumers may respond and may need to:
- seek other food;
- move to an area where the food is in greater supply;
- adapt to climatic change over time.
Failure to respond to availability of food, and the result of disease, may lead to the death of that organism with the consequences being felt by other consumers.
