Question

Identify the incorrect statement from the following about extinction.

• A. Ordovician - Silurian extinction was caused due to global cooling and heating
• B. Algal blooms or global cooling are believed to have caused the late Devonian extinction
• C. Permian - Triassic extinction occurred 250 mya and is believed to have been caused by anthropogenic action
• D. Triassic - Jurassic extinction wiped most of the mammals from Earth

Answer 1

The correct option is C Permian - Triassic extinction occurred 250 mya and is believed to have been caused by anthropogenic action

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). The variety of diverse species is declining as many species are becoming extinct due to various human activities such as pollution, introduction of exotic species, hunting, overexploitation and habitat destruction and fragmentation. This is called anthropogenic extinction.

There have been five episodes of 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. Thus the statement in option a is correct.
• The second mass extinction is called the late Devonian extinction and occurred around 365 mya. It is believed to have occurred due to either global cooling or algal blooms which caused destruction of many marine species. Thus the statement in option b is correct.
• The third Permian - Triassic mass extinction occurred around 250 million years ago and is believed to have been caused due to volcanic activity or asteroid impact. It wiped away most of the vertebrates and almost 96% of the life that existed on earth. Thus the statement in option c is incorrect.
• The fourth extinction is called the Triassic - Jurassic extinction and occurred around 200 mya. It is believed to have been an impact of a volcanic eruption or asteroid hit. It is believed that it wiped out most of the mammals from the Earth. Thus option d is correct.