Themes: Ocean Animals, Ecosystem. Sharks come in many shapes and sizes. Every ocean is home to them. These creatures have lived in the sea for hundreds of millions of years. They continue to be an important part of the ecosystem. Red Rhino Books Nonfiction is the first Hi-Lo children's nonfiction series at a first-grade reading level for students in grades 4–7. Visually appealing fullcolor photographs and illustrations—along with fun fact boxes—keep these books flowing. Also includes prereading comprehension questions along with a 20-word glossary for further reading support.