|Of the many spectacular occurrences that have happened to the Earth in its more than 4 billion years of existence, mass extinctions of its species are perhaps the most fascinating / Photo by: Serge VILLA via 123RF|
Of the many spectacular occurrences that have happened to the Earth in its more than 4 billion years of existence, mass extinctions of its species are perhaps the most fascinating. Currently, scientists are warning that we are on the brink of a sixth mass extinction, as our planet has undergone five mass extinctions over the past millions of years.
Mass Extinctions: Good and Bad
According to ThoughtCo., a premier reference site with a 20+ year focus on expert-created education content, mass extinction refers to a period where a large percentage of living organisms goes extinct or is completely wiped out. It is caused by different events, such as geologic catastrophes, climate change, or even meteor strikes on the Earth’s surface.
There was a time when more than 75 percent of species on Earth disappeared. Scientists were able to spot the occurrence by sifting through global fossil record.
Mass extinction events cause a very rapid period of speciation among the few that have survived. Surviving species can freely spread out since there is so much room for them. Many habitats during these periods need to be filled. Eventually, these species adapt to the new environmental conditions and reproduce away from their original populations. At this point, they can be considered a brand new species and biodiversity expand rather quickly.
After mass extinction events, there has been an increased biodiversity on Earth. This is because the species don’t have to compete for food, shelter, resources, and even mates. These events are nothing new because according to scientists, species go extinct all the time for various reasons. Previous reports estimated that at least 99.9 percent of all species of plants and animals that ever lived are now extinct.
Scientists have discovered at least five different mass extinctions that referred to as the Big 5. They have significantly reshaped the levels of life on Earth.
|There was a time when more than 75 percent of species on Earth disappeared. Scientists were able to spot the occurrence by sifting through global fossil record / Photo by: Thanarak Worakandecha via 123RF|
Ordovician-Silurian Extinction: More than 440 million years ago
Scientists suspected that the Ordovician-Silurian Extinction was caused by a continental drift and subsequent climate change, eliminating up to 85 percent of all living species. According to National Geographic, the official magazine of the National Geographic Society that primarily contains articles about science, geography, history, and world culture, this mass extinction involved massive glaciations that locked up much of the world’s water, causing sea levels to massively drop. Some of the species that were largely affected were the trilobites, the eel-like conodonts, and shelled brachiopods.
Devonian Extinction: 365 million years ago
Studies suggested that around 75 percent of species were lost in the Devonian Extinction. For instance, trilobites, which survived the first mass extinction, were nearly exterminated during this time. It was caused by the quick cooling of air temperatures, lack of oxygen in the oceans, volcanic eruptions and/or meteor strikes. There are several theories as to why the Devonian Extinction occurred. One of them was the quick colonization of aquatic life of the land. Many aquatic organisms adapted to live on land. As a result, there were fewer autotrophs to create oxygen for all of sea life were left, leading to mass death in the oceans.
Permian-Triassic Extinction: 250 million years ago
Scientists considered the Permian-Triassic Extinction as the deadliest of all the mass extinctions. They believe that a comet or asteroid triggered the massive die-off, wiping out more than 90 percent of all species on the planet. It nearly ended life on Earth. During this period, global temperatures increased while oceans acidified and stagnated. This was caused by an enormous volcanic eruption that filled the air with carbon dioxide. After this extinction, marine life developed a complexity not seen before. Some of the new species that emerged were snails, urchins, and crabs.
|Scientists considered the Permian-Triassic Extinction as the deadliest of all the mass extinctions / Photo by: serpeblu via 123RF|
Triassic-Jurassic Extinction: 210 million years ago
The Triassic-Jurassic Extinction was caused by massive floods of lava erupting from the central Atlantic magmatic province, wiping about 20 percent of all marine families, including all non-dinosaur archosaurs, many large amphibians, and most mammal-like creatures. Other causes were flooding basalt eruptions, climate change, and asteroid impact. Scientists said that this extinction paved the way for the evolution of dinosaurs.
Cretaceous-Tertiary Extinction: 65 million years ago
Scientists refer to this as the K-T extinction because it brought on the extinction of dinosaurs. This is caused by a combination of climate change, asteroid impact, and volcanic activity, ending 76 percent of life on Earth. The Cretaceous-Tertiary Extinction allowed for the evolution of mammals on land and sharks in the sea.
New Analysis Showed a Total of Six Mass Extinctions
Scientists need to record the number of mass extinctions that occurred millions of years ago to determine their causes. For so long, we believed that there have been only five of them. A recent study conducted by researchers from the New York University concluded that Earth experienced a previously underestimated severe-mass extinction event. They referred to it as the Guadalupian Extinction, which lasted from 272 to about 260 million years ago.
According to an article by Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, the researchers found out that the Guadalupian Extinction occurred at the same time as the Emeishan flood basalt eruption. Michael Rampino, a professor in New York University's Department of Biology and a co-author of the analysis, said, "Massive eruptions, such as this one release large amounts of greenhouse gases, specifically carbon dioxide and methane, that cause severe global warming, with warm, oxygen-poor oceans that are not conducive to marine life.”
The researchers reported that the end-Guadalupian event is a mass extinction due to the losses in the number of species and overall ecological damage.