(ORDO NEWS) — During its long history, the Earth has experienced several periods when many species of living organisms disappeared in a geologically short period of time.
The reasons for this were very different – from volcanic eruptions to an asteroid impact. Now scientists have determined what caused the very first mass extinction, which happened 550 million years ago.
Environmental changes, such as global warming or a reduction in oxygen, can lead to mass extinction of animals, as well as profound disruption and reorganization of the ecosystem.
However, this was not the first and not even the most serious attempt by the planet to “strangle” the creatures living on it, because a quarter of a billion years before that, about 550 million years ago, the Earth experienced the first mass extinction in history.
His victims were primitive animals, representatives of the so-called Ediacaran biota : some of them looked like creeping leaves, others – like sessile jugs, others – nothing at all.
Researchers from the Virginia Polytechnic Institute (USA) analyzed the composition of the mass extinction victims (only 20 percent of the species can be found in later geological layers) and found that it did not “mow down” everyone indiscriminately.
On the contrary, it acted surprisingly selectively: mainly those species whose structure and behavior (for example, large size with a relatively small body surface and a sedentary lifestyle) showed a strong dependence on the level of oxygen dissolved in water suffered.
In other words, the cause of the first mass extinction was most likely suffocation: for some reason, which the researchers are not yet able to name, sea water lost a significant part of the oxygen dissolved in it.
Perhaps this was due to global warming (warm water loses oxygen more easily, in addition, microorganisms that absorb this gas during breathing multiply more actively in it), caused by the movement of tectonic plates, volcanic eruptions, a collision with an asteroid or something else.
Despite the sad consequences for the animals of those times, the mass extinction served to “clear the foothold”, after which the marine ecosystems began to be dominated not by bizarre “drafts”, but by slightly more familiar animals, among which are quite modern-looking sponges, jellyfish and ctenophores .
Scientists also warn that in the situation of the current climate crisis, the data of 550 million years ago look alarming: who knows if the warming of the World Ocean will lead to a new attack of terrestrial suffocation?
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