”Kids do ecology”

You bet it’s for kids. Anyhow, it outlines the basis for further studying of ecology. In it you can find: good explanations of ecology concepts ( go to Learn about ecology →Frequently asked questions), a list of main biomes with their characteristics and an article about endangered species; among other stuff.

I also recommend this page, especially for the ones doing the IGCSE. It’s simple, in a wikipedia style, but helpful as a summary (note some things belong to higher years) if you’re revising.