ABSTRACT
Several mass extinctions have occurred during the Earth’s history. The Cretaceous – Tertiary Boundary (K-T) Extinction caused the loss of at least three-quarters of all species known at that time including the dinosaurs. The cause of this mass extinction is a controversial subject among scientists but the fossil evidence of it’s occurrence is abundant.
INTRODUCTION
The K-T Extinction occurred 65 million years ago. Many species perished in that extinction. Today evidence for this extinction can be seen in the fossil record. Biological, botanical and geological evidence at the Cretaceous – Tertiary Boundary show that some enormous event occurred that caused mass extinction of life on the Earth. Controversy about the cause of the K-T extinction exists with two main theories currently being in favour. One theory is called Intrinsic Gradualism and believes the cause of the K-T Extinction was a slow and gradual Earth generated event, caused by intense volcanic activity and the effect of plate tectonics. The second theory is known as Extrinsic Catastrophism and proposes that the K-T Extinction was caused by a sudden and violent catastrophic event such as the Earth being struck by a meteor or asteroid. The K-T Extinction supports the concept of Punctuated Equilibrium in evolution because surviving species evolved and others were exterminated. This creates the stepladder effect of evolution seen in the fossil record .
THE K-T EXTINCTION
The Cretaceous period occurred between 144 and 65 million years ago. The K-T Extinction is an event that happened at the end of this period 65 million years ago. By the beginning of the Tertiary period eighty-five percent of all species disappeared, making it the second largest mass extinction event in geological history (“The End-Cretaceous (K-T) Extinction”, accessed 2000).
Among the species that perished were the dinosaurs, pterosaurs, belemnoids, many species of plants, except ferns and seed-producing plants, ammonoids, marine reptiles and rudist bivalves. Severely affected organisms included planktic foraminifera, calcareous nannnoplankton, diatoms, dinoflagellates, brachiopods, mollusca, echinoids and fish. Mammals, birds, turtles, crocodiles, lizards, snakes and amphibians fared much better and were mostly unaffected by the End-Cretaceous mass extinction (“The End-cretaceous (K-T) Extinction”, accessed 2000...
... middle of paper ...
...pdated 1995, accessed 3 Sept. 2000), Dino Buzz – What killed The Dinosaurs ? – Current Arguments,
http://www.ucmp.berkeley.edu/diapsids/extinctheory.html
Lowood, H. 1998 (updated 7 Sept 1999, accessed 30 June 2000), Stanford Presidential Lectures and Symposia in the Humanities and Arts, Stephen Jay Gould,
http: //prelectur.stanford.edu/lecturers/gould/index.html
Smith, P.L. 1997a (updated 1997, accessed 3 Sept. 2000), Biological Evidence,
http://www.science.ubc.ca/~geol313/lecture/kt/biol/biol.htm
Smith, P.L. 1997b (updated 1997, accessed 3 Sept. 2000), The Marine Realm,
http://www.science.ubc.ca/~geol313/lecture/kt/biol/marine/marine.htm
Smith, P.L. 1997c (updated 1997, accessed 3 Sept. 2000), The Terrestrial Realm,
http://www.science.ubc.ca/~geol313/lecture/kt/biol/terres/terres.htm
Smith, P.L. 1997d (updated 1997, accessed 3 Sept. 2000), Geological Evidence,
http://www.science.ubc.ca/~geol313/lecture/kt/geol/geol.htm
“Speculated Causes of the End-Cretaceous Extinction” (accessed 3 Sept. 2000),
http://www.wf.carleton.ca/Museum/cretcause.htm
“The End-Cretaceous (K-T) Extinction” (accessed 3 Sept. 2000),
http://www.wf.carleton.ca/Museum/cretmass.htm
In this paper Martin is arguing that late quaternary or near time extinctions where caused by human activity or as he calls it “overkill”. Martin recognizes that there have been many forces that have triggered extinctions in the planet on the past but disagrees with the idea that near time extinctions where caused by some commonly believed causes like climate change, disease or nutrient shortage. He argues that the arrival of humans to different continents, islands and the subsequent excessive hunting, the introduction of diseases and other competitors and predators was the cause of extinction of a great number of species “As our species spread to various continents we wiped out their large
The question of what caused the extinction of megafauna during the Late Pleistocene period is one that archaeologists have struggled to answer for decades, but why should it matter? Discovering with certainty the cause of megafaunal extinction would simultaneously prove or disprove any of the proposed implications of each existing theory regarding this massive extinction.
The Permian-Triassic Extinction is a mass extinction that occurred between the Permian and Triassic geologic time periods approximately 250 million years ago; it is the deadliest of all extinctions that have occurred on Earth. In addition, during the Permian-Triassic extinction the continents of today existed as one supercontinent known as Pangaea. This was the first time in history where continental or land mass exceeded that of the ocean. This was also before dinosaurs of the Triassic period roamed Earth, during this time animals such as the therapsids, and Synapsids such as the Pelycosaurs, insects and amphibians also occupied Earth. Fauna that existed during the Permian period includes Gymnosperms, or seed producing plants such as the Conifers. Other animals that existed during this time include marine life such as brachiopods (clams), bryozoans (coral-like skeletons), bony fish and sharks, as well as crinoids (sea urchin like creatures). According to National Geographic, about 90 percent of all the animals and fauna of this period perished, the marine life was hit the hardest wi...
Fossil records inform us that the mass extinction occurred 65 million years ago. This landmark coincides with and marks the Cretaceous-Tertiary (K-T) boundary. There appeared to be relative consensus among scientific professionals that an asteroid impact caused the mass extinction. According to this theory, “debris from the asteroid’s impact would have superheated the atmosphere so that vegetation burst i...
“...99.9 per cent of all [species] that have ever existed are now extinct.” (Benton 1) After one hundred and sixty million years of domination, the reign of the dinosaurs ended in fire and ice. Sixty five million years ago, the largest volcanoes in the history of the Earth erupted across what is now India, effectively annihilating the dinosaurs by spewing out noxious gas and ash, that effectively blocked out the sun killing off most vegetation and breaking the food chain, leaving the dinosaurs to starve. Compared to other groups of animals the dinosaurs were the most vulnerable to such a climatic event and the result was the end of the dinosaurs’ glorious evolutionary history.
“Sex, Drugs, Disasters, and the Extinction of Dinosaurs” is written by Stephen Jay Gould, professor of geology and zoology at Harvard. This essay is one of more than a hundred articles on evolution, zoology, and paleontology published by Gould in national magazines and journals. It tells about scientific proposals for the extinction of dinosaurs – a confusing but an exciting problem that humanity tries to solve. By analyzing and describing each of the claims for the reptiles’ demise – sex, drugs, and disasters – Gould differentiates bad science from good science and explains what makes some theories silly speculations, while the other, a testable hypothesis.
Throughout Earth’s history there have been many changes. These changes have consisted of temperature fluctuations, atmospheric differentiations, extinctions of various plant and animal life, etc. Over time everything seems to have evolved in some way form or fashion. However, the Permian Era extinction was different from all the rest. This extinction affected every form of life, but especially the marine life. Researchers have stated that 93-97% of all Earths species went extinct during this period of time. This essay will explain how a once blossoming progressive era turned into Earths most catastrophic event.
Earth has gone through five fully major extinctions before. We currently are in the process of Earth’s sixth mass extinction. This mass extinction is closely related in severity to the extinction of the dinosaurs. Earth’s extinctions are broken into three different areas. The first area was the large number of animals caught by hunter-gathers. The discovery of agriculture led to the second area of extinction, wildlife habitats. These wildlife habitats were destroyed due to humans starting to stay in one area.
The EBSCOHost article looked very accurate it provided the source, author, the document type, subject terms, summary, author affiliations, and etc. The Google article didn’t provide any of that. The EBSCOHost article was error free and it also, stated that none of the information from the University of Texas at Austin School of Law Publications content cannot be copied or used on multiple websites because it’s content is copyrighted. That shows that the content from EBSCOHost is authentic and directly from the source. Where as, the Google article looked error free didn’t provide me with anything that said it was copyrighted. Which means the article can be one’s opinion or some made up nonsense. Therefore, the Google is not as credible or accurate as the EBSCOHost article. Both articles doesn’t have an editor or someone who verifies the information. The only difference is that EBSCOHost owns all rights to it’s content and all of content is copyrighted. Where as, the article from Google more so resembles a
The most significant event of the Cretaceous era came at its end. Nearly 65 million years ago, the second most severe mass extinction in earth’s history occurred. This resulted in the loss of around 80% of species living at the time. Though nowhere near as severe as the end-Permian mass extinction, the end-Cretaceous extinction is the most well known mass extinction event. This is due to the violent event that caused it the extinction, as well as the chapter of earth’s history that it closed: the Dinosaurs. The Cretaceous Event ( often shortened to K-T event) Of the animals that were killed off were the flying reptiles (pterosaurs) and the last few mosasaurs and plesiosaurs, both early marine reptiles. Many mollusks and species of microscopic plankton were killed. Terrestrial plants suffered mass extinction as well. Almost 60% of terrestrial plants were lost. This led to high extinction rates among insect populations, especially insects that were highly specialized to feed on just a few types of plants had it the worst. It took approximately 9 million years for the global insect populations to recover from the Cretaceous extinction. Immediately after the extinction, the earth saw an explosion of short term species who respond well to fire, or other external disturbance. Evidence of the catastrophe comes from a thin rock layer deposited worldwide just after the impact. It is dominated by fossil plants whose descendants recover quickly after fires of other disturbances, such as Fire Weed in Alaska. The causes of the Cretaceous extinction are still being debated by paleontologists. Scientists agree that the main cause of the extinction was a...
seems like it happened so sudden, as geologic time goes, that almost all the dinosaurs
The Jurassic period is known as one of the most interesting periods of time in earth’s history, mainly for the awe-inspiring creatures many of which have gone extinct, the most remarkable being the dinosaurs. Life in the ocean during this time was also extremely diversified and amazing for the creatures it beheld. The Jurassic occurred from 199.6 to 145.5 million years ago, following the Triassic Period and preceding the Cretaceous Period within the Mesozoic Era. The supercontinent of Pangea began to drift apart during this time. Right before the Jurassic period began, a major extinction event occurred wiping out much of the life on earth. The events that unfolded afterwards gave life to a new planet.
Sutter, John D. “Should scientists ‘Jurassic Park’ extinct species back to life”, www.cnn.com 5 May 2014, 22 May 2014
Many different theories exist as to why the dinosaurs went extinct. We know for sure most dinosaurs died out around 65 million years ago. The majority of scientists agree on a number of theories as to what brought the end of the dinosaurs. The most popular theory is that an asteroid ended the reign of the dinosaurs. Another theory, massive climate change in the pre-historic atmosphere, caused all the dinosaurs to die. Some scientists believe that mammals out competed dinosaurs for food and other resources. The last theory that dinosaurs died due to a large amount of volcanism comes up in scientists list of theories as well. Many different theories of why dinosaurs went extinct include extinction by asteroid, mammals outcompeting dinosaurs, climate change and volcanism.
...rgest extinction of all time; destroying almost all species including life on land as well as life in the ocean. The PT extinct in comparison to the KT extinction was very quick, only taking place over 160,000 years. This extinction divided the Permian period from the Triassic period. This took place during the formation of Pangea. After this extinction, new plants and animals emerged; specifically the animals that came before the dinosaurs. The KT extinction, although not as large as the PT extinction, created the largest known volcanic eruption known. This extinction killed off all of the dinosaurs as well as half of the species that lived during that time period because of a giant meteor the size of Manhattan. Even though much of the plant life died out during this time because of the lack of sunlight, it did not become extinct, but died and eventually came back.