Lesson 10_Extinction and its different types

about extinction and its types

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2. Extinction

3. Evolution and Extinction Extinctions are the result of organisms not able to adapt fast enough to meet the changing needs. Sometimes, catastrophic events might trigger mass extinctions which might give other species a clean slate.

4. Extinction  occurs when every member of a  species  (kind) of living thing has died. All types of life may suffer extinction, including animals, plants, fungi, and bacteria. In fact, most biologists think that more than 99 percent of the species that have ever lived are now extinct. Extinction plays an important part in  evolution  (the development of living things over time).

5. How Extinction Among Species Occur

6. Background extinction  Gradual extinctions occur all the time through the ordinary mechanisms of evolution. Changes in the environment Species also become extinct when they are unable to compete for limited resources.

7. 2. Mass extinction  C atastrophic episodes where vast numbers of species have died out suddenly. Scientists divide Earth’s history into periods. A mass extinction may mark the boundary between two periods.

8. The Ordovician extinction  O ccurred about 445 million years ago, when relatively little life had spread to land. The mass extinction was caused largely by global cooling and an   ice age,  a period when glaciers covered much of the Earth.

9. The Devonian extinction  O ccurred about 360 million years ago. It mainly affected ocean life, especially coral reefs. The mass extinction likely had several causes, some of them related to the spread of root-bearing plants on land.

10. The Permian extinction  O ccurred about 250 million years ago. It was by far the worst mass extinction. Most scientists believe that the Permian extinction was caused in large part by tremendous volcanic eruptions in what is now Siberia. Gases released by the eruptions caused rapid climate change and acid rain, and reduced oxygen levels in the oceans.

11. The Cretaceous extinction  O ccurred about 65 million years ago. Most scientists believe the mass extinction was caused by an asteroid impact. This impact could have thrown large amounts of dust and debris into the atmosphere. These materials would have blocked sunlight and caused a long winter, killing much plant life. There also were giant volcanic eruptions in India at this time.

12. Modern extinction Many hundreds of species have become extinct in the last 500 years. Famous examples include the   dodo , the  Tasmanian tiger , and the  passenger pigeon . Scientists believe that extinctions are occurring so rapidly that many species disappear before they can be identified.

13. Extinct Birds