Sexual Reproduction: Why have so many biological systems developed sexual reproduction?.How Did It Start? What are the different hypotheses of origin of life? Did life begin on this planet, was there inanimate intervention (such as a meteor hitting the earth) or intelligent, extraterrestrial design? What are the mechanisms of biorhythms and chronobiology? Why is magnetite in living creatures?.What is Life? Are there life forms in the universe that are not based on carbon? Is there a clear boundary between carbon-based life and Artificial life?.How did biological organisms start? Are the conditions necessary for the origin of life narrow or broad? How are the sizes of cells, organs, and bodies controlled? Did life start on this planet or was there an extraterrestrial intervention (for example a meteor from another planet) ? Why have so many biological systems independently developed sexual reproduction? What constitutes a species? Why is life on Earth made out of certain atoms such as carbon and oxygen? Are there life forms in the universe that are not based on carbon? Is there a clear boundary between carbon-based life and Artificial life? Does the concept of a non-physical thinking being make any sense or is life always instantiated in matter? The chapter concludes with a discussion of the idea that life is the means by which the universe comes to know itself. Related questions are then investigated in an attempt to explore the boundaries of the physical domain we call 'life'. What is life? The first chapter is called 'What is life?' It starts with some of the history of biology and gives a version of the 'textbook answer' that might typically be found in an introductory biology textbook. Each chapter starts with a question, maybe the sort of question a small child would ask, and explores the implications of that question out to the limits of the current state of research and then moves on into speculation about what might be discovered in the future. The goal of this textbook is to serve as an unorthodox introduction to biology. Answers to all questions about biology can start with what is already known and then move on to what remains to be discovered, what remains unsolved. We welcome contributions of new questions about biology on the Grist page.

This book is dedicated to the idea that asking questions is important. No matter how much we know about living organisms, there is always more to learn.

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