Introduction When looking at any mass extinction event, there are a number of questions that will invariably need to be answered. When did it happen? How many species were affected? Which ones were they? What was the cause of such widespread death? How did some species survive while other, thriving ones were wiped out completely? For four of the “Big Five” mass extinction events, the Ordovician-Silurian, Permian, Triassic-Jurassic, and Cretaceous-Paleogene, the answers to these questions are all agreed upon, almost universally. The remaining event, known as the Late Devonian mass extinction, lacks a definitive answer as to the cause. Understanding the cause of extinctions, especially ones of such magnitude as the Big Five is incredibly important. …show more content…
It is known that this event marks the boundary between the Frasnian and Famennian ages. Beyond that, little is known with certainty. Not even the dates that it took place during are completely agreed upon. Recent radioactive dating indicates that it most likely happened around 376 million years ago (Racki, 2005, p. 11), though that date can vary by up to two million years, as is shown in the figure. This lack of a definitive date makes connecting short term and sudden events, such as an asteroid impact or volcanic eruption, nearly impossible to link to the event. What is mostly agreed upon, though, is that the Devonian extinction “event” was actually a series of smaller events that took place over the span of about a million years (McGhee Jr, 2005, p. 40). During this time, reef-builders, such as stromatoporoids and corals, were affected greatly. Many brachiopods, trilobites, and fish were also heavily impacted. In all, about 70% of invertebrate species were extinct by the end of this event, almost all of which lived in marine environments (House 2009). Land animals were left more or less unphased by this event that eliminated so many aquatic …show more content…
First of all, there must be some supporting evidence of the purported cause. Without it, a hypothesis can be quickly ruled out as a possibility; it can’t have caused such widespread deaths if there’s no proof it ever happened. The claim must also account for which species went extinct. Within that comes justification for why some species went essentially unaffected. The distribution of extinctions must also be supported, such as why some environments and locations appear to have been hit harder than others. In the case of the Late Devonian mass extinction, it would have to provide reason for why it was almost exclusively marine invertebrates that
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
“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.
On May 22, 1915, an explosive eruption at Lassen Peak devastated nearby areas and rained volcanic ash farther 200 miles to the east! This explosion was the most powerful in a series of eruptions from 1914 through 1917. ...
In order to better understand these "implications," it is necessary to define and explain the major theories regarding North American megafaunal extinction. The two most widely supported theories are those of environmental change and overkill. Two theories finding less support within the field are those of hyperdisease and "keystone herbivores."
Long-term survival of a species depends on its ability to adapt to changing environmental conditions (Murphy, 1994). Genetic diversity within a species, which has taken 3.5 billion years to evolve, makes adaptations to these changing environments possible. Unfortunately, the rate of extinction of genetically diverse organisms is rapidly increasing, thus reducing this needed biodiversity, largely due to the human impacts of development and expansion. What was an average of one extinction per year before is now one extinction per hour and extinct species numbers are expected to reach approximately one million by the year 2000 (WWW site, Bio 65). As a result governmental and societal action must be taken immediately!
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.
After I read this book, The Sixth Extinction: An Unnatural History. I realized it talks about the extinctions the Earth has confronted and the purposes behind these. In the beginning, the general concept of "extinction" was not popular yet it finally developed as an idea in the revolutionary France. This was achieved by one creature, the creature now discussed to the American mastodon and exclusive Cuvier who is alluded to as the "Father of fossil science". The reason of this book is that we can stamp with extensive precision five noteworthy "extinction" of life on this planet and the sixth is approaching. As one would imagine, the creator clarifies there is no genuine complete recognizable proof of the purposes behind the initial five, just
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...
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.
In the early nineteen hundreds, dinosaur fossils were discovered and recognized around the globe. Greedy scientists and civilians, searching for their own prize skeleton, rushed to rip bones out of the ground, destroying the fossils as they went. It was not until later in the century that scientists and paleontologists began pondering how such widespread creatures disappeared. Currently, paleontologists debate the two main hypotheses of how the classic dinosaurs died: from volcanic activity or an asteroid impact. Although they result in the same outcome, the volcanic and asteroid hypotheses differ in key elements: the actual event, the environment's stress, and the impact on life.
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.
Almost 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species went extinct (Beaz). Although the cause of this mass extinction is debatable, many speculate that global warming was the killer. Because Pangea was breaking up into Laurasia and Gondwanaland, there was widespread volcanic activity caused by the rifting, increasing atmospheric carbon dioxide. The massive release of this greenhouse gas increased global air temperatures and resulted in acidified oceans along with rising sea levels. If this is the case, the life in the ocean would have died at a significant rate. Many families of brachiopods, gastropods, bivalves, and marine reptiles became extinct (Rafferty). An important trace fossil known as the phylloceratid ammonoid was able to survive, and they gave rise to the explosive radiation of cephalopods later in the Jurassic Period, as well as evolved into many different forms during the later Cretaceous (End Triassic Extinction). This extinction event ranks fourth in severity of the five major extinction events over geologic history
The prominent theory is that dinosaurs died in a fiery death due to an asteroid crash on Earth, but is that really what caused their mass extinction? Every scientist has a theory, and with so many out there it was hard to just pick one, they all made sense. It is completely possible for a volcano to have killed the dinosaurs, or even an asteroid. Another popular theory was the ice age. These were all plausible reasons for the extinction of dinosaurs, and that’s when the combination theory was discovered. It is a theory that states there were several factors that played into the extinction of the dinosaurs. The dinosaurs died due to the environmental factors that are included in the combined theory.
The Permian Period commenced 298.9 million years ago and ended 252.2 million years ago, ranging from the close of the Carboniferous Period and the beginning of Triassic Period. About 250 million years ago, at the end of the Permian period, something killed some 90 percent of the planet's species. The species of animals in the seas survived no more than 5 percent. On land less than a third of the large animal species made it; nearly all the trees died (Hillel J. Hoffman, 2015). Marine life was devastated, with a 57% reduction in the number of families (Sepkoski, 1986). Oceanic life suffered the most, but terrestrial life forms were also greatly affected. All major groups of oceanic organisms were affected with the crinozoans (98%), anthozoans (96%), brachiopods (80%) and bryozoans (79%) suffering the greatest extinction (McKinney, 1987). The world, today, is alive because of the remaining 10 percent. The events that took place were in phases and some of the causes were an asteroid hitting the earth, sea level fluctuations flood basalt eruptions, a drop in oxygen levels from the acid rain caused by volcanic ash, calamitous methane release, etc.