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

Hint: Extinction means end or dying out of something. Mass extinction refers to the extinction of a large number of species within a short period of time. It happens due to various factors such as climate change, asteroid impact.

Complete answer:
Mass extinction refers to dying out of a large number of species within a short period of geological time. It is also known as the Biotic Crisis. Some common causes of mass extinction are climate change, asteroid impact, overpopulation, pollution, global warming, increasing sea levels, etc.
There have been 5 major mass extinctions on earth millions of years ago. They are as follows:
> Ordovician- Silurian (435 mya)- It is the second largest of the five major mass extinctions. It lasted for about 44.6 million years and 60% of the marine genera. The cause of this extinction appears to be the movement of Gondwana into the south polar region leading to global cooling, formation of glaciers and decrease in sea level. The end of this event was %marked when glaciers started to melt, and sea levels were stabilized.
> Late- Devonian (370 mya)- This event eliminated 70-80% of species. It occurred at the beginning of the Ensian stage. This extinction included 4 distinct events: lower zlichov, taghkanic event, kellwasser event and hangenberg event. It was caused due to environmental change
> Permian- Triassic Extinction (240 mya)- It is popularly known as the ‘Great Dying’. It was one of the most severe extinctions in which 96% of marine species were killed and 70% of terrestrial vertebrates were killed. It was caused by volcanism, impact events, hydrogen sulfide emissions.
> Triassic- Jurassic Extinction (214 mya)- It is the end of the Triassic period and marks the beginning of Jurassic extinction. It was a result of massive volcanic eruptions, global warming, and climate changes. Affected animals were mammals, amphibians, cephalopods.
> Cretaceous- Paleogene Extinction (66 mya)- It is commonly known as K-T extinction. It was a mass extinction of plant and animal species. It was caused due to asteroid impact, volcanic eruptions

So, the correct answer is option C.

Note: We are in the middle of a biodiversity crisis as the majority of species of animals are becoming extinct every day. According to recent studies, by 2050, 50% of species on earth will be either extinct or endangered. The possible reason for that could be global warming, habitat destruction, increasing sea levels.