Why Is Extinction Important To Evolution?

Extinction: A Radical History is a book published by writer, professor and activist Ashley Dawson. It was published on the 22nd of April 2016. Dawson talks about multiple broad subjects in his book like how Capitalism is the main source of mass extinction. By doing so, he takes into account the lengthy history of the Homo Sapiens species, their activities and their discoveries and how us, humans, have affected today’s biodiversity, and probably the future of our planet Earth. He also offers solutions but are they realistically possible? Today, we no longer face natural risks like asteroids and comets. As Dawson states we now face anthropogenic risks like climate change and biodiversity loss which leads to a change in the earth’s ecosystem.

There have been 5 mass extinctions in Earth’s existence. The names of these are (from most recent to least recent): Cretaceous–Paleogene, Triassic–Jurassic, Permian–Triassic, Late Devonian, and Ordovician–Silurian. The most well known mass extinction, Cretaceous-Paleogene, was theorized to have occurred through a massive comet or asteroid impact. A cold winter created by the impacting object forbid any plants and plankton to carry out photosynthesis. During this time, about three quarters of all life went extinct. This happened approximately 66 million years ago. Most life forms went extinct, with some ectothermic species and tetrapods weighing less than 25 pounds. Although everything seemed to look hopeless, adaptive radiation caused evolution

Extinction is defined as: the state or situation that results when something, such as plant or animal species, have died out completely (Merriam-Webster). The World Wildlife Foundation, otherwise known as the WWF, says that experts estimate that the loss of animals is estimated to be between 1,000 and 10,000 times higher than the natural extinction rate. Experts calculate that between 0.01 and 0.1% of all species become extinct each year. Although this may seem like quite low numbers it reality is it quite large. If the lower estimate is correct, then out of the estimated two million species on the planet, then an estimated two-hundred and two thousand species will become extinct each year. If the larger estimate is correct and that there are an estimated 100 million different species on the planet, then that results in ten thousand and one-hundred thousand species who become extinct each year (WWF). Experts say that of all the species that existed on this planet, 99.9% are now extinct (PBS). However, what if they could be brought back?

Throughout the lifetime of the Earth, there have been various scientists who have hypothesized various extinction events. The following essay will cover the five major extinction events, otherwise known as the “Big 5 Mass Extinction Events”. According to Wikipedia (2016), a mass extinction is “a widespread and rapid decrease in the amount of life on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms”.

Mass extinction is defined as the global decrease in diversification during a period of time reasons due to any events that occurred in history of earth. Mass extinction occurs when a great number of species goes into extinction globally.

Natural selection was a Natural selection is the micro evolutionary process where certain species develop certain traits that help them adapt and survive

The earth has been around for 4.6 billion years, and over this time 99.9% of all of the species that have existed on earth have gone extinct. (Barnosky, et al) Palaeontologists characterize mass extinctions as times in Earth’s history when the Earth loses more than three-quarters of its species in a geologically short period of time. This has occurred 5 times over the past 540 million years, and scientists are now suggesting it is happening a 6th time. We are in the midst of a sixth mass extinction that has the potential to wipe out many species of importance, and humans have a profound impact on it.

Are we on the brink of a sixth mass extinction? Many say yes, but there is also hard evidence saying no. Nonetheless, scientists can prove five mass extinctions in history. The first mass extinction happened roughly around 445 million years ago. It was named the Ordovician Extinction. The species affected were known as Graptolite, which are different types of sea creatures. Their demise on Earth lasted around only one million years. Around sixty to seventy percent of the species disappeared, and now the remaining species have evolved into something new. The extinction was likely because of a short and dangerous ice age, or the formation of the Appalachian mountains. It was likely that glaciers formed over the oceans and caused the sea levels to rapidly drop, killing the species.

One reason a mass extinction can be plausible is because a lot of the previous periods have also been caused by mass extinctions. A lot of these extinctions were triggered by some change in the weather or atmosphere. Earth’s climate today, is becoming increasingly warmer and carbon dioxide levels are increasing which might potential be too much for humans and animals to take.

Since the beginning of life itself, some species have lived and prospered while other species have gone extinct never to be seen again by mankind. Because of this, some would claim that extinction is natural and not significantly problematic to the world that we live in. Others, however, understand that due to climate change, habitat loss, and poaching, more and more species are becoming endangered which leads to a chain reaction that can be devastating to ecosystems. Species such as the Chinook salmon, gorillas, tropical sharks, and polar bears are all directly affected by climate change, species such as northern spotted owls, Sumatran tigers, and lemurs are greatly harmed due to habitat loss, and species such as the sea turtle, Javan rhinoceros, African elephant, and the Red-Fronted Macaw are all affected by poaching driving them all closer and closer to becoming extinct.

An endangered species face a huge risk of extinction in the coming years. This could be due to habitat loss, natural occurring disasters, pressure from other species and climate change. Sometimes the biggest factors due to population decrease are Human Beings themselves. Some species that are facing a threat to extinction are Chimpanzees, Amur Leopard, African Wild Dog and of course the Mountain Gorilla.

Dinosaur extinction could arguably be the most important event that contributed to world history. Without the extinction of dinosaurs, the human race would not exist let alone world history. These beautiful creatures appeared during the Triassic period about 231.4 million years ago. These creatures lived everywhere in the world including Antarctica. During the Triassic period all of the continents were morphed together into one called the Pangaea making travel a lot easier. Since the climate was different Antarctica had forest and was able to inhabit life. The dinosaurs disappeared at the end of the cretaceous period about 65 million years ago to an unknown source.

There have been five well known extinctions on this earth. The one most well known is the mass extinction that ended the dinosaurs. Mass extinction is often described as the elimination of a large number of species in a short period of time. Despite what many think, the elimination of species is almost commonplace at this point. The Earth is currently in the middle of a sixth mass extinction, and it’s been caused by the human race.

Habitat destruction, deforestation, ozone depletion, global warming, and poaching. These actions and ecological happenings are creating a world where animals are going extinct at rapid rates. Our world is on the brink of what scientists believe is the sixth mass extinction. Unlike the five previous mass extinction, the latest one killing a majority of the dinosaurs, the main causes for this current extinction are anthropogenic reasons, not natural events.

Over 98% of all organisms that have lived on Earth are now extinct. A mass extinction event occurs when a large number of species die out within a small time frame (relative to the age of Earth). Mass extinctions are intensively studied for both cause and effect, as there is usually room for debate regarding catalysts that precede the extinction and the massive influx of new biological species that follows. There have been five major mass extinctions, dubbed the “Big Five,” that have wiped out at least 50% of the species living at those times. The most well known mass extinction of the Big Five, with the decimation of every species of non-avian dinosaur, is the Cretaceous-Paleogene