Reading Metrics
Grade Level
Middle Grades (MG 4-8)
Book Level
7.9
Points
1.0
Fiction/Nonfiction
Nonfiction
Word Count
7680
Points per Word
0.00013
Page Count
48
Points per Page
0.020833
Description
This book explains the causes and limits of variation in species, such as blood groups and disposition to disease, and why variation is so important to their survival.