Primary consumers feed solely on plants.Their food consists of leaves, grasses, fungus, flowering shrubs and other hedging plants. In the food chain, plants are the producers that are fed on by herbivores. Examples of primary consumers are cows, goats, antelopes, rabbits, giraffes and zebra.
Secondary consumers feed on primary consumers (herbivores). They are referred to as carnivores. Examples are lions, leopards, cheetahs, tigers, hyenas, eagles and wild dogs. Omnivores are animals that feed on both plants and other animals. For this reason, they fall in both categories of consumers - primary and secondary. Examples of omnivores are humans, pigs, squirrels and domestic dogs. Tertiary consumers, on the other hand, are carnivores that solely feed on meat. Examples are hawks, sharks and snakes. Plants are referred to as producers because, unlike animals, they can make their own food in the process called photosynthesis.
In the food chain, all consumers need energy for their sustenance. For example, humans need nutrients to keep their organs functioning optimally. When one organism feeds on another one, energy is lost. Therefore, there should be more producers than primary consumers. Similarly, primary consumers are more than secondary consumers, while secondary consumers are more than tertiary consumers. If the predators are more than their prey, they will lack food at some point, affecting the equilibrium.