The process of natural selection is strongly linked to the environment. Students will learn in this standard set that the environment has changed over time. The geologic record provides evidence of both the environments of the past and the plants and animals that inhabited them. The focus in this standard set is on using the geologic evidence to better understand life on Earth, past and present.

This standard set presents two great ideas from the geologic sciences to make clear the relationship between life and geology: (1) the concept of uniformitarianism; and (2) the principle of superposition. Uniformitarianism refers to the use of features, phenomena, and processes that are observable today to interpret the ancient geologic record. The idea is that small, slow changes can yield large cumulative results over long periods of time. Standard 4.c states a simplified version of the principle of superposition when it indicates that the oldest rock layers are generally found at the bottom of a sequence of rock layers. The principle of superposition is the basis for establishing relative time sequences (i.e., determining what is older and what is younger). Geologic records indicate that both local and global catastrophic events have occurred, including asteroid/comet impacts, that have significantly affected life on Earth. Both the evidence and the impact on life should be addressed in this standard set.