If you need some guidance in creating scientifically accurate and plausible habitats and organisms for your exobiology project, the Speculative Evolution Wiki is a great resource to start with. There is a page on the types of alien planets thought to exist. There is a page on alternative biochemistries. There are pages covering the wide variety of approaches Earth life takes to common problems, such as movement, perception, reproduction, defense, and the various ways that an organism might draw energy from its environment.
Written by Daniel Noe, WayOutLife.com