AR Book Level
6.8
AR Points
2
Word Count
13,584
Interest Level
Middle Grades (MG 4-8)
Genre
Nonfiction
AR Quiz #
30730 EN
About this book
This book explains the occurrence of biological clocks, which, for example, "tell" birds when and where to migrate, plants when to unfurl their leaves, and which affect human beings in various physical and emotional ways.
