First we learn what defines a living thing and understand that they need air, water and food. It is the food that provides the energy to grow. Plants are living things that make their own energy through a process called photosynthesis. Animals who eat just plants are called herbivores and that is how they get their energy. Certain animals eat certain parts of a plant—for example one might just eat the leaves and another seeds or nectar. Among the herbivores there are grazers and browsers. Next readers meet the carnivores. These are usually predators that eat meat.