Evidence for Evolution: Fossils
- Fossils are the preserved remains of organisms, or the traces left by organisms, such as footprints, burrows and faeces
- These remains can be preserved, e.g. in rocks, by the process of petrification, during which the tissues of organisms are replaced with minerals
- The fossil record is small in relation to the number of organisms that have ever lived, due to the conditions for fossilisation being so rare
- We can tell from fossils that organisms have changed significantly over millions of years
- Fossils, as well as the rocks they are found in, can be dated, allowing us to accurately put fossil organisms into a sequence from oldest to youngest, and therefore see how organisms have changed through evolutionary time
- The fossil record shows the kind of progression that the theory of evolution would lead us to expect, with older fossils showing simpler life forms and complexity increasing with time
- The sequence of fossils aligns with ecology groups:
- Plant fossils appear earlier in the fossil record than animals
- Plants with the ability to be pollinated by insects appear before insect pollinators
- Fossils can show evidence for transitional species, showing how one species could evolve into another e.g. Ambulocetus is a fossil that links amphibians with early whale-like organisms, and Archaeopteryx appears to link reptiles with birds