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Earth's fossil record

Review your understanding of Earth's fossil record in this free article aligned to NGSS standards.

Key points

  • Life has existed on Earth for billions of years. Evidence of life on Earth, and how it has changed over time, is found in the fossil record.
  • The fossil record is made up of all the fossils that have been found, along with their relative ages. Scientists can look at patterns in the fossil record to understand the history of life on Earth.
    • For example, the fossil record shows us that there has been an overall increase in the complexity of organisms over time. It also shows us that there has been an increase in organism diversity.
    • The fossil record shows us when specific types of organisms appeared, went extinct, or changed.
    • And, the fossil record shows us that there have been mass extinctions in Earth’s past. A mass extinction is when many species die off around the same time.
Fossilized organisms in rock.
A diverse set of fossilized marine organisms. These organisms lived about 450 million years ago. Image credit: “Echinodermata Ordovician Fossils” by RomanDeckert, CC BY-SA 4.0.

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