Which consumers eat only plants?

Food webs are cycles of what eats what. All living things, plants and animals, need energy in order to survive. Plants (like grass for example) create energy from sunlight by photosynthesis. This is then transferred to herbivores (like rabbits) which eat the plants. Predators (such as foxes) then eat the herbivores and the energy is transferred once more. These transfers of energy are what we call food chains.