6. Mass Extinction Found

Mass Extinction Discovered
Mass Extinction Discovered - The findings may also offer insight into how humans are endangering aquatic life. As a result of various agricultural and wastewater applications that cause nutrients such as phosphorus and nitrogen to enter the marine and river ecosystems, the number of algae that decomposes in the water and absorbs oxygen has increased. Modern animals may face similar challenges as "dead zones" spread, where the oxygen level in the water is too low to support life. According to Xiao, "this study helps us understand the long-term ecological and geological effects of oxygen deficiency events." Scientists have found a 6th mass extinction hidden in Earth's ancient past Dickinsonia (centre) and the smaller, anchor-shaped Parvancorina (left) are impressions of fossilized Ediacaran sandstone found in South Australia's Nilpena Ediacara National Park. (Photo courtesy of Scott Evans; image credit)

According to recent research, the first mass extinction documented on Earth occurred 550 million years ago as a result of the global decline in oxygen levels. The Ediacaran period, which culminated 550 million years ago, was a golden age for marine life. In the ocean, feather-shaped petalonamides were absorbing nutrients, slug-like Kimberella grazing on microbial mats, and jellyfish ancestors were starting to cause waves.

But after that, 80% of life on Earth disappeared, leaving no evidence in the fossil record.

According to a recent study, these lost fossils are evidence of Earth's oldest major extinction disaster.

These lost fossils are evidence of Earth's oldest major extinction, according to a new study. A sharp global decrease in oxygen caused the extinction of these first large, complex animal groups; this result could have implications for present-day ocean ecosystems, which are threatened by human activities.

According to the study's lead author Scott Evans, a postdoctoral fellow at Virginia Tech, this is the first known major extinction event, according to the animal's fossil record. Its connection to climate change makes it consistent with all major mass extinctions.

Mass extinctions have served as an evolutionary testing ground for animals at least five times. During the Ordovician-Silurian and Devonian extinctions (440 million and 365 million years ago, respectively) many sea creatures disappeared. Then came the Permian-Triassic and Triassic-Jurassic extinctions, also called the "Great Dying", which affected both terrestrial and oceanic vertebrates and occurred 250 million and 210 million years ago, respectively. At the end of the Cretaceous period, about 66 million years ago, the most recent mass extinction wiped out about 75% of all plants and animals, including the nonavian dinosaurs.

Paleontologists have been debating for some time whether to add another catastrophic extinction to this list. For a long time it was unclear whether the sudden decline in fossil diversity that occurred 550 million years ago was the result of a rapid global extinction event.

One explanation is that the Ediacaran fauna was destroyed by competition from early trilobites, armored and often helmeted marine arthropods. Another possibility is that the fauna of the Ediacaran period still exists, but the conditions for preserving Ediacaran fossils did not exist until 550 million years ago. According to Evans, people were aware that the biota was changing during this period. But there were serious concerns about what the possible causes might be.

To address these issues, Evans and colleagues created a database of Ediacaran fossils that other researchers had previously documented in the academic literature and categorized each item according to factors such as location, body size, and diet. Of the 550 animal species that scientists categorized from 70 million years ago, only 14 were still alive 10 million years later. They found neither a change in dietary strategy that would imply the extinction of Ediacaran species as a result of competition with early Cambrian animals such as trilobites, nor a significant change in the conditions required for the preservation of fossils.

But all surviving species had one thing in common: body designs with a high surface area-to-volume ratio that could help animals adapt to low-oxygen environments. Based on this finding, and geochemical evidence that oxygen declined 550 million years ago, a mass extinction catastrophe may have occurred due to limited oxygen availability in the ocean towards the end of the Ediacaran. On November 7, the scientists published their findings online in the journal Proceedings of the National Academy of Sciences.

Shuhai Xiao, professor of geobiology at Virginia Tech and one of the study's co-authors, explained that they looked at the selectivity model, which includes what disappeared, what survived, and what evolved after extinction. It turns out that organisms that could not survive in low-oxygen environments were deliberately destroyed.

It's still unclear why oxygen levels dropped in the Ediacaran's final years. Less dramatic explanations are also possible, such as changes in ocean recharge levels, such as volcanic eruptions, tectonic plate movements, and asteroid impacts, according to Evans.

Whatever the cause, this mass extinction has undoubtedly had an impact on the future evolution of life on Earth, and it could have implications for researchers studying the origins of animal life.

According to Evans, the majority of Ediacaran species do not resemble any of the animals we are familiar with. It is possible that this early extinction event opened the door for more modern life forms, as we began to observe more and more creatures after this event.

The findings may also provide insight into how humans are endangering aquatic life. As a result of various agricultural and wastewater applications that cause nutrients such as phosphorus and nitrogen to enter the marine and river ecosystems, the number of algae that decomposes in the water and absorbs oxygen has increased. Modern animals may face similar challenges as "dead zones" spread, where the oxygen level in the water is too low to support life.

According to Xiao, “this work helps us understand the long-term ecological and geological effects of oxygen deficiency events.”

source: livescience

 

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