A food chain is an organized series of living things linked together by an alimentary (food related) relationship. Animals draw the energy needed for survival from their food.
At the base of such a chain one finds the producers. These are terrestrial plants or aquatic ones (algae, phytoplankton). They make their own organic matter from nutrients, CO2, and light (photosynthesis).
The animals situated one step up on the chain are the first level consumers: the herbivores. They are the prey of the second level consumers: the carnivores.
A carnivore that doesn’t have any predators is called an apex predator. These are situated at the top of the chain.
An arrow stands for “…is eaten by…”. A food chain is made up of links that can also be part of other chains. They are branches of a vast alimentary network.
This animation omits the role of decomposers. These are organisms and microorganisms that degrade dead organic matter (wastes, dead plants and animals). They provide the larger part of the nutrients that are recycled by the producers.