This module contains four units dealing with natural selection (and evolution), population balance, exchange cycles, and environmental protection. Each unit includes coverage of why the topic is important, what is known about the subject, and the evidence that led to our current level of understanding. There is also a short biography of a famous scientist in each field of inquiry, hazards associated with the topic, an on-line flash-card self quiz, and a set of hands-on activities. Teacher's guides are also provided for each unit. Registration and log-in are required to access these.