Biology books discuss what makes up life in its most basic cellular form. There are nine main categories of biology, and questions answered in a biology book may differ depending on if the book is about one specific category or all of them. In general, biology books answer questions both broadly and specifically about the structure and matter that makes up living things.
The nine main categories of biology are biochemistry, botany, cellular biology, ecology, evolutionary biology, genetics, molecular biology, physiology and zoology. An example of a biochemistry question that a biology book may answer is, "What is a macromolecule?" A question on botany that a biology book may answer is, "Why do plants die?"
Biology books may contain the answer to the cellular biology question, "What is the structure of a cell?" and the ecology question "What is an ecosystem?" "Why are humans generally taller than they were 100 years ago?" is an evolutionary biology question that a biology book may answer, and "Why is my hair red?" is a genetics question that a biology book may answer.
Answers to the questions "How are biology and chemistry related?" and "What is a molecule?" may be found in a biology book that includes a section on molecular biology. A physiology question a biology book may answer is "How does my pancreas work?" An example of a question a biology book may answer about zoology is "Why do animals behave in the ways that they do?"