In other situations, the ultimate source of energy comes from chemicals. All of the other organisms in an ecosystem that depend on the primary producers are called consumers . Consumers are not able to obtain and use sunlight energy to sustain themselves. They must feed on either the primary producers or other organisms. These types of organisms are referred to as heterotrophs .
Ecologists make further distinctions between the levels of consumption that occur in ecosystems.
Primary consumers eat only primary producers. These are also known as herbivores . An example of a herbivore would be a rabbit. Secondary consumers are those that feed on herbivores - a carnivore , if you will. An example of a carnivore that feeds on herbivores would be a snake.