How far back are you looking.......

[Church]

As far as I can guess (and since it's a guess, you can ignore me totally), you can do anything you want. Something well-known, like photosynthesis, in itself may not gain very many creativity points, but if you think of a great new way to portray it with your animation, then it's just as good as coming up with the most out-there idea ever. As long as there's some aspect of your animation that will make people say "oh wow, what I great idea!" then you're on the right track. So if photosynthesis interests your group, then go ahead.