Check out these links to take practice tests for each chapter:

Miller Textbook

Chapter 1 - Intro to Environmental Science

Chapter 9 - Human Population

Botkin/Keller Textbook

Chapter 3 - Systems of Change

Chapter 5 - The Biogeochemical Cycles

Chapter 6 - Ecosystems and Ecosystem Management

Chapter 7 - Biological Diversity

Chapter 8 - Biogeography