Experiences on the Voyage of the Beagle. Uniformitarianism, or presently observed causes, readily accounted for all geological forms. Extinct species most closely resemble living ones in same area, suggesting one had given rise to other. In rock strata, progressive changes in characteristics can be seen in fossils from progressively lower layers. Also, the work of Lyell was indicating that the earth was older than the few thousand years that people thought.
Diatoms are single-celled photosynthetic organisms that float in plankton.
This is fossil record for a diatom between 3.3 and 1.6 million years ago. Shows fossil record can be used to reveal origin of new species. Analysis of modern forms indicates that amphibians and reptiles are evolutionary intermediates between fish and mammals. This order fits with the geological succession of the major vertebrate groups. The width of each group indicates the diversity of the group at that time.