Mass Extinction: Ordovician Silurian and Permian-Triassic extinction

Mass Extinction refers to the extinction or loss of a huge amount of biodiversity at once. Our earth is the only planet in our solar system which possesses life. You will be astonished to know that there are over 8.7 million species of life found on earth! There are over 3,00,000 species of beetles, 20,000 species of ants, 20,000 species of orchids, and 28000 species of fish. However, it is also a fact that more than 99% of species that existed millions of years ago have now become extinct. With the passage of time, old species get extinct and new species start to evolve. History has witnessed many mass extinctions around different eras of evolution. In this article, we will look at the various mass extinctions and their causes.

Keyterms: Biodiversity, Planet, Solar system, Evolution, Weather, Ecosystem, Food web, Oxygen, Extinction, Beetles

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What is Mass Extinction?

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Mass extinction is an event where a huge amount of biodiversity is lost due to some causes. Mass extinctions are very deadly events, it leads to a drastic change in the ecosystem, and the food web collapses. It has to be built from the bottom up. Sometimes changes in weather patterns can also cause an extinction event.

Timeline of Mass Extinction

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Types of Mass Extinction

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1. The Ordovician Silurian Extinction 

Ordovician Silurian Extinction happened over 440 million years ago in the Ordovician period. It is one of the severest extinctions of all time. 

• It wiped out 85 % of all marine species present at that time. Most of the species were marine though some lived outside oceans too.
• This extinction actually consisted of 2 extinctions separated by about 1 million years. 
• At that time many environmental changes were happening. Plants were starting to grow on land. The carbon dioxide-rich air was changing to oxygen-rich air. 
• It is said that this lead to a drastic decline in temperature which led to the extinction of species that couldn't sustain this change.

Ordovician Silurian Extinction

2. The Devonian Extinction

The Devonian Extinction led to the extinction of mostly tropical marine life forms and did not affect terrestrial life much. The exact reason behind this extinction has still not been understood till now. 

3. The Permian-Triassic extinction

The Permian Triassic extinction is the largest extinction earth has ever witnessed. It is also said that the earth became almost life-less after this extinction. 

• Estimates are that almost 96% of marine species and about 70% of terrestrial species were lost during that time. 
• The species that survived the Ordovician Silurian extinction became extinct during this extinction. It is also sometimes referred to as the great dying. 
• The causes of this extinction are not very clear but it is found that abrupt volcanic activities led to an increase in the temperature followed by global warming events.
• The oxygen level in oceans reduced drastically. Some terrestrial species like tetrapods that survived took 30 million years to recover from this extinction.

The Permian-Triassic extinction

4. The Triassic-Jurassic extinction

The Triassic-Jurassic extinction happened about 200 million years ago just at the end of the Triassic era. This extinction removed almost 78% of terrestrial and marine species from earth. 

• This event is ranked fourth on the scale of severity. Due to this extinction, the dinosaurs came into existence. 
• This extinction is found to happen around the same time when the supercontinent “Pangea” divided.
• The reason for this extinction is not very clear but studies suggest that it was caused by climate change, rising sea levels leading to an increase in carbon dioxide levels in the air.

5. The Cretaceous-Tertiary Extinction

The Cretaceous-Tertiary Extinction happened 66 million years ago. This was the event that led to the extinction of almost all dinosaur species and other dominant vertebrates. 

• If this extinction wouldn’t have happened then humans wouldn’t have come into existence. This is the most studied and researched event of history and it explains a lot about the evolution of species that are now present on the earth.
• This extinction occurred due to the impact of a large meteorite or asteroid that hit the place which is now the Gulf of Mexico’s Yucatan Peninsula. 
• The 100 miles wide asteroid was sufficient to increase global temperature. The impact was so devastating that the debris and dust remained in the atmosphere for years blocking the sun’s light. This led to impact winter. 
• Due to lack of sunlight, the photosynthetic organisms died and those who fed on them also died. This completely destroyed the food chain.

The Cretaceous-Tertiary Extinction

6. The Sixth Mass Extinction

We are on our way to witnessing the sixth mass extinction. Humans are going to be the main reason behind this. 

• Currently, if we observe the species that have become extinct we can calculate the rate of extinction of upcoming times. Studies have found that this rate is higher than a lot of events in history. 
• About 10,000 years ago humans developed agriculture. While they gained enough knowledge about different crops and foods they started manipulating the environment for their own benefit. 
• Humans have developed certain machines which are polluting the air, destroying forests. 
• Humans are carrying out a lot of environmental changes throughout the world and if the change is fast then other species wouldn’t be able to adapt to it. 
• Adaptation requires time. If the change is fast, many species that are not able to adapt will become extinct. 

The Sixth Mass Extinction

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Causes of Mass extinction

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The causes of mass extinction are as follows:

• The changes in sea levels lead to change in the composition of oxygen and other necessary elements required for survival. This change disrupts the marine ecosystem and leads to the extinction of species.
• The meteorites and asteroids coming from space, volcanic disruptions, etc creates anoxic conditions. The meteorite that fell on earth during the end-Permian period led to the extinction of a lot of species. 
• The increase in temperature due to various events leads to the melting of glaciers. These glaciers melt and increase the seawater level.

Causes of Mass Extinction

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Things to Remember

• Mass extinction is an event when a vast majority of species are lost due to some causes.
• The Ordovician Silurian extinction wiped out almost 85% of animal species from the world.
• The Permian Triassic extinction was the severest extinction of all time.
• The supercontinent Pangea got divided during the Triassic Jurassic extinction.
• Triassic Jurassic extinction led to the evolution of dinosaurs.
• The Cretaceous-Tertiary extinction removed all the dinosaur species from the earth and created a way for humans.
• Human activities could be the reason for the upcoming sixth mass extinction.
• Adaptation requires a long time. If the change is fast, species cannot adapt and will eventually extinct.

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