Extinction Study Guide

Extinction is the death of creatures or a group of organisms, most commonly an entire species.

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Although the potential to procreate and recuperate may have been lost before this time, the death of the last individual of the species is typically regarded as the moment of extinction. There are different types of extinctions with various causes. Let's learn the impact of extinction and what causes it.

Effects of extinction:

When a species goes extinct, it loses its whole genetic legacy. This might occur naturally due to climate change or as a result of human activity like overhunting or habitat damage.

Despite the ambiguities, there are three essential components to extinction:

  1. Extinction is a possibility for the species as a whole.
  2. Mass extinctions would prepare the way for a huge biosphere rearrangement, with a few successful populations being removed and smaller ones expanding.
  3. There is evidence that Darwin selectively argues for extinction in a few circumstances. It is now difficult to anticipate which species will be the next to go in mass extinction.

Causes of extinction:

Extinction causes Source

1. Asteroid Strikes:

Dinosaurs went extinct millions of years ago due to a meteor strike on Mexico's Yucatan peninsula. Such occurrences triggered the majority of large extinctions. Astronomers are always on the lookout for comets or meteors that might bring humanity's civilization to an end.

2. Climate change:

Another cause that might wipe out terrestrial creatures is climate change. Most large animals could not adjust to the mild shifting temperatures at the end of the last ice age. They died due to a shortage of food and early human hunting. Because of global warming, even contemporary civilization is on the verge of extinction.

3. Habitat loss:

Every species has its safe haven to reproduce and nurture its young. For example, a bird prefers to perch on a tree limb. Forests, which are home to the majority of animals, have been destroyed due to the growth of human civilization and industrialization. Many creatures' numbers have been reduced due to a shortage of space and, eventually, food.

4. Disease:

Various diseases have resulted in the extinction of many humans and animals on the planet. During the Middle Ages, the Black Death killed one-third of Europe's population.

5. Pollution:

Pollution from factories and cars has resulted in a significant decrease in oxygen levels in the atmosphere and water. Many aquatic and terrestrial animals have become extinct as a result of this.

6. Lack of genetic diversity:

When the number of species in a species decreases, the gene pool of that species shrinks. There will eventually be a shortage of genetic variety. For example, African cheetahs have a limited genetic diversity as a result of habitat degradation.

Mass extinctions:

Even though extinction is a constant part of earth's flora and fauna (the great majority of species that have ever existed are extinct), the fossil record indicates five extremely massive extinctions, each involving the extinction of enormous numbers of species. Mass extinctions are distinguishable from the bulk of extinctions, which occur regularly and are referred to as background extinction.

Mass extinctions Source

Relation between speciation and extinction:

Speciation is an evolutionary process by which a new species are formed and develops its own unique characteristics. The rate of speciation measures how many new species appear in an interval of time within a given taxon and a given habitat, region, or ecosystem. The rate of speciation is compared with the extinction rate to help determine the amount of diversity in an ecosystem. If the rate of speciation is higher than the rate of extinction, the number of species present will increase, and conversely, if the extinction rate is higher, the number of species present will fall. Currently the rapid loss of species due to human interference is unlike the mass extinction events of geological history.

Relation between extinction and adaptive radiation:

Many ecosystems are no longer occupied by species after a mass extinction because they have gone extinct. Some species will adapt to their new habitats when new habitats become available. During these periods, evolutionary processes move quickly. To fill those accessible habitats, many new species evolve.


  • Extinction is the death of a creature or a group of organisms, most commonly a species.
  • When a species goes extinct, it loses its whole genetic legacy. To adapt to environmental changes or changes in genetic legacy, species develop into new species.
  • Although extinction is a constant part of earth's flora and fauna (the great majority of species that have ever existed are extinct), the fossil record indicates five extremely massive extinctions.
  • Extinction provides newly available niches that different species can then exploit.


1. What are the 5 extinctions?

The 5 major extinction levels are:

  • Ordovician-Silurian extinction
  • Devonian extinction
  • Permian-Triassic extinction
  • Triassic-Jurassic extinction
  • Cretaceous-tertiary extinction

2. Why did dinosaurs go extinct?

A large meteorite collided with earth, drastically altering the climate that dinosaurs couldn't live in. Many dinosaurs were smothered by ash and gas ejected by volcanoes. Diseases wiped off whole dinosaur populations. Dinosaurs starved as a result of food chain instabilities.

A new study has discovered that dinosaur eggs had long incubation periods, placing the newborn creatures and their parents at threat from predators and other environmental conditions. This might explain why prehistoric species died out because they couldn't reproduce quickly enough after the mass extinction.

3. Is earth due for a mass extinction?

The earth is now undergoing an extinction catastrophe, owing in great part to human exploitation of the planet.

The present extinction rate is between 100 and 1,000 times greater than the pre-human background rate, which is mind-boggling. 'We are unquestionably in the midst of the sixth mass extinction.' On earth, no single species has ever been accountable for such devastation.

4. How are humans causing animal extinction?

Humans also contribute to the extinction of other species through killing, overharvesting, releasing invasive species into the wild, polluting, and converting wetlands and forests to croplands and cities. Even human population increase is causing extinction by destroying natural ecosystems.

5. What was the first extinction? The Ordovician extinction, the first known mass extinction, occurred when most of the earth's life was found in its waters. Marine creatures were among the victims.

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  1. extinction. https://www.britannica.com/science/extinction-biology. Accessed 27 Dec, 2021.
  2. HALTING THE EXTINCTION CRISIS. https://www.biologicaldiversity.org/programs/biodiversity/elements_of_biodiversity/extinction_crisis/. Accessed 27 Dec, 2021.
  3. What are mass extinctions, and what causes them?. https://www.nationalgeographic.com/science/article/mass-extinction. Accessed 27 Dec, 2021.