Benchmark 5F
The Living Environment: Evolution of Life
Grades 6-8, page 124

Many thousands of layers of sedimentary rock provide evidence for the long history of the earth and for the long history of changing life forms whose remains are found in the rocks. More recently deposited rock layers are more likely to contain fossils resembling existing species.

NSES Content Standard C 
Life Science: Diversity and adaptations of organisms
Grades 5-8, page 158
Extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient to allow survival. Fossils indicate that many organisms that lived long ago are extinct. Extinction of species is common; most of the species that have lived on the earth no longer exist.