CK-12 Biology is a high school FlexBook covering cell biology, genetics, evolution, ecology, microorganisms, fungi, plants, invertebrates, vertebrates, and physiology.
CK-12 Foundation is a non-profit organization with a mission to reduce the cost of textbook materials for the K-12 market both in the U.S. and worldwide. Using an open-content, web-based collaborative model termed the "FlexBook," CK-12 intends to pioneer the generation and distribution of high quality educational content that will serve both as core text as well as provide an adaptive environment for learning through the FlexBook Platform™.
checked it out to see what would be in a textbook now a days. glad to see they didn't avoid the topic of evolution at all and didn't cave to the "teach the controversy" creationism bunk.
End chapters are a sex ed class, which was a bit surprising. I was expecting them to save all of that for their "Human Biology - Your Changing Body" textbook.
there's a lot of videos, most link to Khanacademy. Which can be a plus or a minus depending on if you like or have signed up for khan academy. If you are signed up and you can both complete your khan assignments as well as your class.