What Causes Mass Extinctions?

Categories: ExtinctionNature

Extinction is the end of an organism or group of taxa. Extinctions occur when a species becomes unfit for survival in its natural habitat usually to be replaced by another, better-suited species. An organism becomes ill-suited for survival because its environment is changed or because its relationship to other organisms is altered as stated from Credo Reference. The moment of extinction is generally considered to be the death of the last individual of that particular species. Mass extinctions, however, are rare events that only happen every few million years.

Only recently have these events been recorded and scientist have become alarmed at these recent extinctions. Most extinctions aren’t even documented and some predict that most of present species will be gone by the year 2100. Many scientist seek to find out what causes mass extinctions, the consequences of these events, and if another extinction in the near future. In the past 500 million years, five mass extinctions have occurred according to fossil record.

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In each event 50% or more of our planet’s species became extinct (Campell).

They occurred at the end of the Ordovican, late Devonian, the end of Permian, the end of Triassic, and the end of Cretaceous period (Thomas). Of all the mass extinctions, the Permian and Cretaceous periods received the most action. The Permian mass extinction occurred about 251 million years ago and took about 96% of marine animals. It also took a huge toll on terrestrial animals. About 65 million years ago in the Cretaceous period, the earth had another mass extinction (Campell).

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During this day and age, dinosaurs reined the land and pterosaur ruled the sky.

The causes of extinctions can be broken down into two different categories which are, terrestrial and extraterrestrial. Firstly, in terrestrial causes, moving continents can be a major factor in extinctions. When all land masses combine, the global diversity will be lower than the different continents. With this, different species can fill the same ecological environment. This could result in extinction because of competition to gain certain sources of food. An example of this would be bison and kangaroos. Both are counterparts of each other, and would most likely become extinct from competition with each other.

There would not be enough plant life to go around. Another factor could be a globally low sea-level. If the earth had this conditions, it could leave little space for certain organism that live in depths lesser than 1000m as stated from Ellen Thomas. Another cause could be climate changes from cold to hot, or vice versa. Certain species can only survive in certain climates and would die in any other environment. An example of this would be how a penguin can only survive in cold climates. If they were to be put in a jungle, for example, they would not survive the heat.

Their fur is built to keep them warm from the cold weather and they would overheat from the jungles temperature. Another great example of this would be a frog. If you have a frog in the desert, if wouldn’t last even a day. The harsh environment of the desert is too much for it. Frogs have to stay moist constantly, and the hot sun would dry their skin at a rapid pace. Natural disasters can contribute as well, which can include volcanoes, tsunamis, and etc. The Permian mass extinction occurred at a time of an enormous volcanic eruption in what is now Siberia. This was the most extreme volcanic activity in the past half-billion years.

When a volcano erupts, it emits large amounts of sulfur dioxide. When this gas reacts with oxygen and water, it forms acid rain. Also, gases from the volcano may poison organism in the local area. Lack of oxygen can also cause organism to die, which is called anoxia. In anoxia oceans animals and algae can’t survive. These oceans even can produce gases that can escape and harm land-dwelling animals (Thomas). An example of this would be certain zones in the Black Sea In extraterrestrial causes, there are only a few factors that make it up. One of them would be an impact from a large asteroid.

They believe that a large asteroid was the cause of Cretaceous’ mass extinction. A large crater was found in the Caribbean Sea near the Yucatan Peninsula of Mexico, which is about 65 million years old. (Campell) A large impact from an asteroid like this would cause global darkness from the amounts of dust sent into the air. This dust would stop photosynthesis for plants which in all would affect every source of live in the area (Thomas). This darkness would also cause the area to cool which could also kill off organisms. Another would be an impact from a comet, such as the comet that exploded above southeastern Siberia in 1908 (Thomas).

The last factor is a Supernova explosion, which isn’t the case for earth since there is no evidence that this influenced life on earth. The consequences of mass extinctions affect biological diversity greatly. By removing large numbers species, this could reduce thriving and complex communities. These events are random and effect species greatly, permanently removing species with highly advantageous features and change the course of evolution forever. Whenever extinctions occur, a trickledown effect can occur. An example of this could be how a certain plant may go extinct, and a worm eats that plant.

That worm would eventually die out because of the food source being gone. A bird would also be affected by this since it can’t eat that worm which is his only food source. The fossil record shows that it typically takes 5 to 19 million years for the numbers of a species to return to their previous levels. It took 100 million years for marine families to recover from the Permian mass extinction (Campell). Some scientist believes that there will be a sixth mass extinction in the coming decades. They think this, because of continuous human actions in the environment (ActionBioscience).

Recently, golden frogs have begun to disappear across Panama which shows some signs of future extinctions. The things that humans indulge in cause’s climate change and modify the global environment to such extremes that species are now threatened with extinction. In the past 400 years, more than a thousand species have become extinct on a geological scale, which is a very short amount of time. Studies show that many species are declining today at an alarming rate (Campell). In conclusion, mass extinctions have a major impact on the environment and other organisms as well. Extinction is inevitable in a changing world such as ours.

Extinctions occur all the time, but have not been steady recently. It doesn’t matter if the smallest organism becomes extinct or the biggest, all will be affected because of the trickledown effect. A person can’t stop mass extinctions if it is natural, but we could try and stop an upcoming sixth extinction since the cause is human beings. Anything that can be produced while putting the environment first would be the best for every living organism. It’s “jaw dropping” to think that humans can be compared to asteroids or supernovas when taking out mass quantities of plants and animals.

Some scientist believes that extinction plays a major role in organism’s evolution. Maybe humans are a part of natural selection, being a “helper” in an animal’s evolution. Maybe we are just another tool used by nature to reduce the organisms on earth. No one really knows when the sixth extinction will happen. All we can do is try to stop it as much as we can.

Works Cited

  1. “Extinction – Credo Reference Topic. ” Credo Reference Home. Web. 29 Mar. 2011. <http://www. newyorker. com/reporting/2009/05/25/090525fa_fact_kolbert>. Reece, Jane B. “15. 9. ” Biology: Diversity in the Living World. By Neil A. Campell. 6th ed. Boston: Addison Wesley, 2009. 302-03.
  2. Print. Thomas, Ellen. “Mass Extinctions. ” Microsoft PowerPoint Presentation. Web. 29 Mar. 2011. <http://ethomas. web. wesleyan. edu/ees123/mass_extinctions. htm>.

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What Causes Mass Extinctions?. (2020, Jun 02). Retrieved from https://studymoose.com/what-causes-mass-extinctions-essay

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