Mass Extinctions

Introduction

The eradication of a species from the surface of the earth is known as extinction. It happens when a species goes extinct as a result of natural disasters or changes in its relatives' evolutionary processes. According to historical records, the Great Dying, or the longest extinction, took hold countless years ago. Nearly 90% of the species on this planet were affected by the event. Extinct animal species imply that there are no longer any living members of that species. Out of 96,500 species, the IUCN estimates that more than 26,500 are on the verge of extinction. It has 25% amphibians and 40% mammals. Additionally, some experts assert that it takes a species a million years to go extinct.

Causes of Extinction

Extinction is caused by many factors. It can, however, be broadly classified into two categories: natural causes and human causes.

Natural causes

• Variations in Climate − Several species go extinct as a result of the planet's shifting climate. Numerous animals were forced to perish as a result of the harsh weather and low food supply.

• Alteration in Sea Currents − The lifespan of nearby species is drastically shortened by the rising sea level and shifting water currents. Therefore, under this situation, aquatic animals are most at risk.

• Asteroid − Several mass extinctions were brought by meteor or asteroid impacts. For instance, a 93 miles wide meteor that struck 66 million years ago during the Cretaceous-Palaeogene era most likely killed the dinosaurs.

• Disease −Sudden pandemic or epidemic breakout. For instance, the 1918 Spanish flu killed around 100 million people while infecting 500 million people, or almost three equal parts of the whole world's population.

• Invasive Species − Whenever a novel genus encroaches on the territory of any other species already living there, they begin to face off against one another. Thus, only the strongest individuals survive.

• Reduced Genetic Diversity − Occasionally, the gene pool becomes confined because of lesser numbers of any species. The meaning of extinct animal suggests the same. As a result, that species steadily moves from being endangered to extinct.

• Lack of Adaptive Skills − The stronger species replaces the weaker one due to a lack of adaptive abilities. Additionally, species that are unable to adapt to their environment or atmosphere eventually become extinct.

Human Causes

Following are the factors involved in human causes −

• Pollution

• Changing habitat

• Over harvesting

Extinction is the last step in the evolutionary process for every species. One of the main objectives of conservation biology is to comprehend the patterns of extinction and danger. It is significant for two causes −

• Identification of the characteristics that predispose species to become extinct or to persist in the face of human disturbance will lead to the development of a strong explanatory framework.

• A predictive framework could also assist us lessen the influence that humans have on biodiversity by predicting the results of various future situations.

There are currently over 20 different species conceptions in use, and the likelihood of extinction depends on −

• Specific traits of the organism and its phylogenetic groups.

• A specific set of causal processes that affect survival and/or reproductive rates.

• The biological species idea.

What is Mass Extinction?

• Mass extinctions have undoubtedly been among the most dramatic incidents in Earth’s history.

• They are described as relatively brief periods of geological time that were marked by the extinction of multiple geographically widespread higher taxa 1.

• Five exceptionally spectacular events 2 out of nearly 20 such occurrences over the Phanerozoic, or the final 542 million years of world's record, have been recognised.

• Species are groups of organisms that can only reproduce inside the group, and is preferred by many neonatologists (i.e., biologists investigating live species). Extinction seems natural.

• A species is considered extinct when its last member has died, but estimating extinction poses challenges for both palaeontologists and neonatologists. The extinction processes on Earth have featured both gradual and severe occurrences.

‘Big Five’ Mass Extinctions

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Mass Extinction Event	Time frame (mya)	Types of life Affected
End Ordovician extinction	Almost 445 million years ago.	Brachiopods, Gralolites, Echinoderms and Corals.
Late Devonian	Almost 375 million years ago.	Corals, brachiopods, bivalves, and sponges are among the several marine families found on tropical reefs.
End Permian (Permian– Triassic or P/T)	Almost 251 million years ago.	Trilobites, Eurypterids, Mollusca, Brachiopods, and vertebrates made up 57% of all the marine families that were destroyed.
The End Triassic	Almost 200 million years ago.	Sponges, sea vertebrates, giant amphibians, Mollusca phylum. Numerous mammals like reptiles.
The End Cretaceous (Cretaceous– Tertiary or K/T)	About 65 million years ago.	Marine Reptiles, pterosaurs, Ammonites, Dinosaurs, planktons.

Causes of Mass Extinction

The Earth's system itself may possibly contain the roots of major extinctions. Several well-known terrestrial causes of mass extinctions include −

• Large scale volcanic eruptions

• Generation of aerosols and persistent climatic warming

• Release of greenhouse gases

• Flood basalt provinces and large basaltic provinces.

Sixth Mass Extinction

• Much emphasis has been paid to the hypothesis that the sixth mass extinction event is currently taking place.

• There is strong evidence that an extinction event is occurring. Many experts believe that global climate change is one of the primary drivers of the major extinction spasm that we are just now entering.

• For instance, it is believed that till 1800 bird species in tropical Oceania vanished in 2000 years since human colonisation (the majority of which were only recently discovered from subfossil remains).

• The Steller's sea cow and dodo (Raphus cucullatus) both extinct since the 17th century (Hydrodamalis gigas, extinct since 1600s) are two examples of huge mammals, birds, and reptiles whose extinctions are documented in writing.

Conclusion

A mass extinction event occurs when a species disappears far more quickly than it is replaced. This is typically understood as the loss of around 75% of all species over a "short" period of geological time, or fewer than 2.8 million years. Extinction is a method by which animals, plants, or other groups become extinct.

The majority of past extinctions are believed to have been brought on by environmental changes to which the doomed species was either unable to adapt or to which it was so thoroughly forced to adapt that it became a whole new species. The main cause of plant and animal extinctions is now thought to be human impact on the environment, including collecting, hunting and habitat degradation.

FAQs

Q1. What are the types of extinction?

Ans. There are two types of extinctions: Mass Extinction (occur due to events like volcano eruption and earthquake) and Background Extinction (occur naturally).

Q2. How many animals are extinct?

Ans. Approx. 10,000 to 100,000 species are getting extinct every year. This includes around 85 mammals, 159 birds, 35 amphibians and 80 fish species.

Q3. What can we do to stop mass extinction?

Ans. The federal government can establish broad rules to protect the environment. Corporations, communities, and people can have a significant impact by changing corporate behaviour through their purchasing decisions.

Q4. What are the consequences of the sixth extinction?

Ans. The consequences of the sixth extinctions are: Alteration of the environment, overuse of wildlife, pollution, introduction of other species, and population growth.