If you are a world builder who needs to ground your life form designs in scientific plausibility, the podcasts at BEKernWrites.com are a good place to start. Each runs about forty minutes long. Subjects such as biomes, metamorphosis, metabolism, and genetic material are covered by an actual professor of biology. The lectures stick pretty close to describing Earth life most of the time while briefly mentioning some of the variations found across the galaxy. It is not wildly speculative.
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.