Food
Teach preschoolers how each zoo animal has a different diet. To explain the concept, have kids color and create different types of food, each of which can be associated with different types of animals. This might include bamboo for pandas, bananas and ants for monkeys, or meat for carnivorous creatures.
Habitat
Help kids understand habitat and how each zoo animal differs in its habitat requirements. Zoos often have to create artificial habitats to allow some creatures to survive; this might include a cold-weather enclosure for arctic penguins, a tropical environment for Amazonian snakes and frogs, or desert-like open areas for elephants or camels. Show this by creating several fake habitats across the room. Label each one a different type of environment, such as "arctic" and "desert." Designate each child a different type of animal and allow the children to group in the respective habitats.
Behavior
Explain to preschoolers how zoo animals also show many different behaviors. Some animals -- such as snakes or crocodiles -- show a lot of solitary behavior, while most land creatures -- including lions or monkeys -- exhibit lots of social behaviors. Small zoo insects, including ants and bees, will often exhibit extreme social interactions, showing relatively little independence. This allows them to have extremely large societies and remain organized and successful.
Sizes
All zoo animals grow to different sizes as well as at different rates. While a chimpanzee might be roughly the height of a preschool student, a elephant will be closer to the height of the ceiling. To provide a visualization of animal sizes, mark different heights on the wall of various animals. Then, to contrast, line up each child and compare his height to the zoo animal's height.