The biology book begins by explaining the concepts of phylogenetic taxonomy and evolution. There's a two-page spread of the tree of life, followed by a brief discussion of what phylogenetic groupings (like "fungus", "bird" or "reptile") are useful for and when paraphyletic groupings (like "arthropod", "plant" or "mammal") can be more useful. The book takes pains to clarify that this phylogenetic taxonomy is based primarily on observable, current genetic similarity; if, as is extremely plausible, the Precursors created all life, they nonetheless created it in such a way that it fits into this tree and more genetically "related" species are more likely to have similar reactions to drugs and be similar in their internal anatomy. Then the book explains the concept of a food web and illustrates with a sample one.
Eventually, after a disclaimer that none of this necessarily applies to metal heads, the book gets into more contingent facts about life on this planet. A lot of it is like Earth biology: the local people have cells, they have blood and lymph, they have organs recognizable as livers and hearts and stomachs, and they run it all on ATP. But they don't have a separate mitochondrial genome and their blood and bones have cells that are specialized at carrying and storing eco. Most species have the ability to draw energy from eco, instead of or in addition to things like food and oxygen, but the systems for that are woefully inadequate to the energy needs of large, active species, and in some cases animals can survive having mutations that make those systems nonfunctional.
And then it goes on to explain how photosynthesis works, which is not notably different from how photosynthesis works on Earth.
At one point Torn interrupts to let him know the Shadow is coming over soon and wants to meet Cam.