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.
Fossils are a lot like puzzle pieces to help scientists uncover Earth's geologic history. Even though scientists will never discover all the fossils out there - scientists can still accurately decipher Earth's past despite the missing pieces to the puzzle. Even though we don't have all the fossils or the pieces of the puzzle scientists can still can figure out the big picture of Earth's geologic history with the puzzle pieces we do have. Much like figuring out this puzzle of planet Earth shown here.
Fossils Provide Clues about Earth’s Past Environment
Fossil Evidence Reveals Many Mass Extinctions
Comparisons between living organisms and fossil evidence allows scientists to make inferences about the lines of descent.
Anatomical similarities such as these help scientists infer many organisms may have common ancestors in the distant past.
Similarities in Early Development
Scientists can infer evolutionary relationships by comparing the early development of different organisms. For example, the organisms in the figure here look similar during the early stages of development. All four organisms have a tail. They also have a row of tiny slits along their throats. The similarities suggest that these vertebrate species may be related and share a common ancestor.
Fossils of whales show that they have changed over geologic time.
Fossils of horses show that horses have gotten larger over geologic time.
- How does a mold fossil form? What are some real-world examples?
- How does a cast fossil form? What are some real-world examples?
- How does a petrified/permineralized fossil form? What are some real-world examples?
- How does a preserved fossil form? What are some real-world examples?
- How does a carbonized fossil form? What are some real-world examples?
- How does a trace fossil form? What are some real-world examples?