Reading Metrics
Grade Level
Lower Grades (LG K-3)
Book Level
5.7
Points
0.5
Fiction/Nonfiction
Nonfiction
Word Count
1927
Points per Word
0.000259
Page Count
32
Points per Page
0.015625
Description
This book explain how, for most animals, eyes are the most important source of information about the world in a biological sense. The simplest eyes, clusters of light-sensitive cells, appeared about 600 million years ago.