Consumers are any living Organisms that depends on other living things for their energy and nutrients (they cannot make their own food). Essentially, anything that does not photosynthesize is a consumer.
Although this seems clear, it is common for students to have some alternative conceptions or be confused about how to classify certain species. For example, a student may believe humans are producers because we make (cook) our own food. Some students have even tried to argue that they could live by eating fingers, etc. If necessary, there is a simple activity you can do with students to help clarify what it would be like as a human to be a producer. Ask every student to raise a hand palm facing towards the sun (or where the sun would be). Have them hold their hand like that for a minute and think about their favourite foods. After a minute has passed, you can explain that if humans were producers, that is all we would need to do to have energy. Since we cannot live an extended and full life without consuming food for nutrients, we are classified as consumers.
Decomposers are a subset of consumer.
One way in which consumers can be classified is through their feeding behaviors:
- Carnivores (eat only meat)
- Herbivores (eat only plants)
- Omnivores (eat both)
- Detritovores (eat decomposing material)
- Fungivores (eat only fungi), etc.