Fossils are mineral replacements, preserved remains, or traces of organisms that lived in the past. The collection of fossils and their placement in chronological order is known as the fossil record. It documents the existence, diversity, extinction, and change of many life forms and environmental changes throughout the history of life on Earth.
- Thousands of layers of sedimentary rock not only provide evidence of the history of Earth itself but also of changes in organisms whose fossil remains have been found in those layers.
- Erosion and weathering of sedimentary rock layers can cause the destruction of fossils and result in gaps in the fossil record.
- Certain environmental conditions favor certain fossil formations. Therefore, the type of fossils found in an area can explain the environmental changes that have occurred.
- The rapid burial of organisms, which is more likely to occur in marine environments, results in a greater likelihood that the remains of marine organisms will be preserved. Flash floods and volcanic ash falls help preserve land organisms.
- Certain fossilized organisms could only live in specific environments or under particular climate conditions.
- Extinction of life forms as well as how and when new life forms appeared is part of the fossil record.
- Fossils can show structural similarities and differences in organisms over time revealing the vast diversity of life forms that have and continue to exist on Earth.
- Anatomical similarities and differences between various organisms living today and between them and organisms in the fossil record enable the understanding of the diversity of life that has been present on Earth.
- Comparisons between living organisms and fossils also allow scientists to make inferences about the lines of descent.