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.
What Can Fossils Tell Us About Earth's Past?
- Existence of many different kinds of organisms such as the dinosaurs from Earth's long geologic history.
- The diversity of living things that have existed on Earth throughout its long geologic history has changed.
- Many extinctions have occurred throughout Earth's long geologic history.
- Changes (evolution) of many life forms that have occurred throughout Earth's long geologic history.
- Environmental changes that have occurred throughout Earth's long geologic history.
Fossils Provide Valuable Clues about Environmental Changes over time.
The type of fossils found in an area can explain the environmental changes that have occurred over long periods of geologic time. In other words, organisms that have been fossilized in a particular area have very unique adaptations for specific types of environments or climate conditions which are found to be dramatically different today.
General Environmental ChangesWhen scientists examine fossil evidence from all around the world the fossils record suggests that the environment on Earth after Precambrian has generally changed from a marine dominant environment during the Paleozoic Era, to a more tropical environment during the Mesozoic Era, to a relatively cooler environment during the Cenozoic Era.
*WARNING*
This is a very oversimplified version of Earth's history. |
Fossils Typically Found in South Carolina
What does this fossil evidence tell YOU about South Carolina's Environmental Past?
Homologous Structures
A homologous structure is a similar structure that can be found in very different animals, often pointing towards a common ancestor. When animals look very different on the outside yet have certain structures that appear similar in form or function, they have homologous structures.
Anatomical similarities such as these help scientists infer many organisms may have common ancestors in the distant past.
Similarities in Early Development
Scientists also infer evolutionary relationships by comparing the early development of different organisms. For example, the organisms in the figure below look similar during the early stages of their development. All four organisms (including humans!) have a tail. They also have a row of tiny slits (potential gills) along their throats. The similarities suggest that these species may be related and share a common ancestor.
Whale Evolution
According to the fossil record about 65 million years ago during the Mesozoic Era the oceans of Earth were home to many fierce marine reptiles. Then, along with large, land-based dinosaurs, those marine reptiles went extinct. About 50 million years ago, some groups of mammals appear to have taken advantage of the more open oceans and began to invade the sea. Today, about 100 mammal species inhabit the oceans, but one group evolved amazing adaptations for life in the water - whales!
Whales have evolved several adaptations to survive in the water. But they kept the basic body plan of all mammals. If you compared your own arm and hand with the flipper of a whale, at first glance they would look very different, but beneath the skin the arrangement of bones is very similar.
Such similarities are called homologies and are most likely the result of descent from a common ancestor. |
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Topic Tips
- Although the debate is still on - the fossil record does document the existence, diversity, extinction, and change of many life forms and environmental changes throughout the history of life on Earth.