GENETICS AND EVOLUTION
EVOLUTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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They find more fossils of plants.
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They find fossils of animals that died suddenly.
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They find a sudden disappearance of many fossil species.
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They find evidence of changes in Earth’s atmosphere.
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Detailed explanation-1: -Mass extinctions were first identified by the obvious traces they left in the fossil record. In the strata corresponding to these time periods, the lower, older rock layer contains a great diversity of fossil life forms, while the younger layer immediately above is depauperate in comparison.
Detailed explanation-2: -Answer and Explanation: Scientists know when a mass extinction took place because they can date the rocks that a fossil is found in to determine its age. Past a certain rock layer that indicates an era of time, they may discover that no fossils of a previous species are found.
Detailed explanation-3: -The exact nature of this catastrophic event is still open to scientific debate. Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth’s climate that happened over millions of years.
Detailed explanation-4: -Answer and Explanation: The most likely reason that a species might disappear from the fossil record while investigating rock layers is that it went extinct.
Detailed explanation-5: -BP: Nowadays, scientists are aware of five mass extinction events in the past, starting with the End-Ordovician Extinction 450 million years ago and up to the End-Cretaceous Extinction that killed off the dinosaurs 66 million years ago (see chart).