Question

Match the following

Mass extinction	Time period
1. Ordovician - Silurian Extinction	a. 200 mya
2. Triassic - Jurassic Extinction	b. 60 mya
3. Late Devonian Extinction	c. 365 mya
4. Cretaceous - Paleogene Extinction	d. 440 mya

Choose the correct option:

• A. 1-a, 2-b, 3-d, 4-c
• B. 1-c, 2-d, 3-a, 4-b
• C. 1-b, 2-c, 3-d, 4-a
• D. 1-d, 2-a, 3-c, 4-b

Answer 1

The correct option is D 1-d, 2-a, 3-c, 4-b

Mass extinction is catastrophic and widespread and it is a global event where relatively major groups of species are wiped out in a short period when compared to normal extinction (due to natural causes). There have been five episodes of such mass extinction of species since life originated on earth.

• The first mass extinction (Ordovician - Silurian extinction) happened 440 million years ago (mya) which occurred due to global cooling and a heating event. Abundant plant life removed carbon dioxide from the air, causing global cooling and glacier formation. This led to a drop in sea levels, reducing habitat. Later came global warming and sea level rising again. Species that were adapted to cooler climates could not survive in the hotter climate.
• The second mass extinction is called late Devonian extinction and it occurred 365 mya. Global cooling or massive algal blooms are believed to have been causes for the mass extinction of almost 75% of all species on earth.
• The third Permian - Triassic mass extinction occurred around 250 million years ago. It is believed to have been caused due to volcanic activity or asteroid impact which wiped away most of the vertebrates and almost 96% of the life that existed on earth.
• The fourth extinction is believed to have been an impact of a volcanic eruption or asteroid hit. It is called the Triassic - Jurassic extinction and occurred around 200 mya.
• The Cretaceous - Paleogene extinction occurred around 60 mya. It is the fifth mass extinction due to an asteroid hit on earth which led to the destruction of various species and completely wiped away all the dinosaurs.
• Sixth mass extinction which is called holocene extinction started around 11,000 years ago and it is continuing till present time. It is an anthropogenic extinction caused due to mindless human intervention. The current species extinction rate is 1000 times faster than the earlier extinction rate.

Mass extinction	Time period
1. Ordovician - Silurian Extinction	d. 440 mya
2. Triassic - Jurassic Extinction	a. 200 mya
3. Late Devonian Extinction	c. 365 mya
4. Cretaceous - Paleogene Extinction	b. 60 mya