Food Chains Within a Food Web
- A producer, also known as an autotroph, is an organism in the first trophic level that makes its own food, typically by absorbing energy from sunlight via photosynthesis. Plants, some bacteria, and algae are examples of producers.
- A primary consumer is an organism in the second trophic level that obtains its energy by consuming plant matter. Organisms in this category are called herbivores. Examples of primary consumers include sheep, grasshoppers, and koalas.
- A secondary consumer is an organism in the third trophic level that obtains its energy by feeding on organisms that eat producers. Organisms in this category are called carnivores. Examples include wolves and snakes.
- A tertiary consumer is an organism in the fourth trophic level that obtains its energy by feeding on secondary consumers. Examples include owls and seals.
- A quaternary consumer is an organism usually at the top of the food chain that obtains its energy by feeding on tertiary consumers. An example is a hawk that eats an owl, which is a tertiary consumer.
Because all organisms eventually die, scavengers, detritivores, and decomposers exist. A scavenger, such as a vulture, is an animal that feeds on dead plants or animals or on refuse. A detritivore, such as an earthworm, is an organism that gets its energy by feeding on dead organic material, particularly plants. A decomposer is an organism, such as a bacterium or fungus, that breaks down dead materials and organic wastes. All of these organisms break down decaying matter and return nutrients and minerals to the ecological community.It is not uncommon for consumers to feed at more than one trophic level. For example, when humans eat only plants, such as tomatoes, they are classified as primary consumers. However, humans can be secondary consumers if they eat beef from cattle.