Life maximizes biodiversity; this is the hypothesis of this book. An atmosphere favorable for life, including high oxygen and the ozone layer, and favorable nitrogen and carbon dioxide levels stimulated increases in biodiversity. Symbiosis drives diversification and macroevolution; e.g. bacteria makes nitrogen available to plants. Ecosystems interact symbiotically. Horizontal gene transfer, often mediated by viruses, is common, drives major evolutionary transitions, and is “symbiotic evolution." These observations and others suggest that life has created a positive feedback loop stimulating biodiversity. key selling features: Describes a hypothesis that ecosystems maximize biodiversity Suggests modified version of the dominant paradigm in population biology and evolution Discusses specific examples of events and phenomena that positively affect the diversity of life Presents a new view likely to elicit deeper discussions of biodiversity