California Science Test (CAST) Practice Exam 2026 – Your All-in-One Guide to Success!

When classifying animals by what they eat, a creature that relies only on plant material is called an herbivore. Herbivores obtain energy by grazing on grasses and leaves, or munching fruit and seeds—think of cows, rabbits, or deer. This contrasts with carnivores, which eat meat, and omnivores, which eat both plants and animals. Bacteria are microorganisms, not animals, so they don’t fit the category of “an animal that eats plants.” A cell is the basic unit of life, not an animal, so it isn’t describing an animal’s diet either. Therefore, the term that best describes an animal that eats only plants is herbivore.