Research an endangered species and write a report on your findings. Speak to experts at universities and zoos, as well as doing online and library research into the subject. Describe why the species is endangered, what efforts are made to prevent their extinction, and include as many statistics as possible as illustration -- climate change and local economic factors often play a part. Some critically endangered species include the Ethiopian wolf, Torrent tree frog, Slender seahorse and Wandering albatross.
Set up experiments to test the sense of smell of pet dogs. Hide selections of differently scented substances to find out which majority of dogs (ask friends and neighbors if you can study their dogs as well as your own pet) sniff out the quickest. See which smells they prefer by observing their reactions, which substances attract them the most, and if they seem particularly excited by certain scents. Write up the results of your experiments along with descriptions of dog's olfactory systems and why they are so refined; survival factors such as smelling potential predators and finding food are main reasons.
Construct a questionnaire designed to check the overall physical and emotional health of a person. Ask questions about how often and how much a person exercises, how well they feel physically and mentally, how fulfilling their social life is, and whether they suffer from stress. Also ask if they noticed any changes since owning a pet, if they are a pet owner. Survey neighbors and friends with the questionnaire, distributing it equally between pet owners and non-pet owners. Write up the results for the science fair.
Hand out questionnaires to owners of different types of dog. Ask questions about temperament, eating preferences, sleeping habits, how playful the dogs are, how quick they learn new tasks, and how much exercise they need. Try to give surveys to two or three owners of every breed to compare a decent sample of each type. Write a report describing similarities and differences between breeds, based on the results of the survey.