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.
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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. |