When studying zoology, students often learn about what animal cells look like. You can create 3D models of animal cells and write a short paper to explain the differences between animal and plant cells.
Purchase live crickets at a pet store and put them in two different containers. Place one container in a warm environment and the other in a colder environment and observe which temperature makes crickets more active. You can conduct a similar experiment with two butterfly gardens placed in different temperatures and determine whether temperature affects the growth of butterflies.
Learn about animal behavior and intelligence. For example, play recordings of different bird sounds and see whether or not a cat reacts to them. Are hamsters smarter than mice? Create a maze, placing a treat at the end, and time hamsters and mice as they travel through the maze to see which can complete the maze fastest. For a less complicated project, choose an endangered animal to research and determine what reasons led to the animal becoming endangered and what can be done to increase that animal's population.
If you have a fish tank at home you can use it to conduct research and experiments. Research what elements should be included in a tropical fish tank and then actually set up and observe whether fish survive in the tank, or research the differences between fresh water and tropical fish tanks and determine which would be the best type of tank to have. You can also purchase goldfish and place them in bowls of varying sizes to determine whether the size of the bowl affects the behavior and lifespan of the goldfish.