2 books · Ages 4–8 · Chapter Books
Biomes of the World is a 2-book series for ages 4–8 by Martha E. H. Rustad. Each book stands alone — start anywhere.
Start anywhere — each book stands alone.
That said, Animals of the Great Barrier Reef and Animals of the Arctic Tundra are great first picks.
No particular order needed — browse and pick what catches your eye.