Question

How many times mass-extinction has occurred on earth so far?

• A. Two times
• B. Four times
• C. Five times
• D. Only once

Answer 1

The correct option is C Five times

An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the amount of life on Earth. Such an event is identified by a sharp change in the diversity and abundance of macroscopic life. It occurs when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity and abundance of life.
There have been five mass extinction events throughout Earth's history.
1. The first great mass extinction event took place at the end of the Ordovician, when according to the fossil record, 60% of all genera of both terrestrial and marine life worldwide were exterminated.
2. 360 million years ago in the Late Devonian period, the environment that had clearly nurtured reefs for at least 13 million years turned hostile and the world plunged into the second mass extinction event.
3. The fossil record of the end Permian mass extinction reveals a staggering loss of life: perhaps 8095% of all marine species went extinct. Reefs didn't reappear for about 10 million years, the greatest hiatus in reef building in all of Earth history.
4. The end Triassic mass extinction is estimated to have claimed about half of all marine invertebrates. Around 80% of all land quadrupeds also went extinct.
5. The end Cretaceous mass extinction 65 million years ago is famously associated with the demise of the dinosaurs.
Thus, option C is correct and other options are wrong.