Take a few minutes to learn some biology from a nice animation. I’ll be focusing on one the players in this story.
Oh, and the homework answers:
2. Big time, radical changes. No oxygen, no ozone, no plants, no animals. The planet would contain pockets of microbial life forms.
If you want plants and animals, you’ll need these reactions. Or at the very least, you’ll find these reactions to be very, very helpful.