Here are recommended books on biology topics for rocket girls aged 6 and up,
Coral Reef Animals. Francine Galko. (6-8 years) Heinemann (2003). Describes coral reefs, where they can be found, the animals that inhabit them, and how to protect them.
Nature’s Adventures by Mick Manning and Brita Granstrom (ages 6 to 9) The authors give simple advice to budding naturalists about what to look for at home, at the beach, or in a forest.