Extinction is the dying out of a species. Extinction plays an important role in the evolution of life because it opens up opportunities for new species khổng lồ emerge.
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A dinogorgon skull protrudes from a rochồng with the South African scrubland in the background.Photograph by Jonathan Blair
When a species disappears, biologists say that the species has become extinct. By making room for new species, extinction helps drive sầu the evolution of life. Over long periods of time, the number of species becoming extinct can remain fairly constant, meaning that an average number of species go extinct each year, century, or millennium. However, during the history of life on Earth, there have sầu been periods of mass extinction, when large percentages of the planet’s species became extinct in a relatively short amount of time. These extinctions have sầu had widely different causes.
About 541 million years ago, a great expansion occurred in the diversity of multicellular organisms. Paleobiologists, scientists who study the fossils of plants and animals to lớn learn how life evolved, hotline this sự kiện the Cambrian Explosion. Since the Cambrian Explosion, there have sầu been five mass extinctions, each of which is named for the geological period in which it occurred, or for the periods that immediately preceded and followed it.
The first mass extinction is called the Ordovician-Silurian Extinction. It occurred about 440 million years ago, at the kết thúc of the period that paleontologists & geologists Call the Ordovician, and followed by the start of the Silurian period. In this extinction event, many small organisms of the sea became extinct. The next mass extinction is called Devonian extinction, occurring 365 million years ago during the Devonian period. This extinction also saw the over of numerous sea organisms.
The largest extinction took place around 250 million years ago. Known as the Permian-Triassic extinction, or the Great Dying, this sự kiện saw the kết thúc of more than 90 percent of the Earth’s species. Although life on Earth was nearly wiped out, the Great Dying made room for new organisms, including the first dinosaurs. About 210 million years ago, between the Triassic and Jurassic periods, came another mass extinction. By eliminating many large animals, this extinction event cleared the way for dinosaurs khổng lồ flourish. Finally, about 65.5 million years ago, at the kết thúc of the Cretaceous period came the fifth mass extinction. This is the famous extinction sự kiện that brought the age of the dinosaurs to an end.
In each of these cases, the mass extinction created niches or openings in the Earth’s ecosystems. Those niches allowed for new groups of organisms khổng lồ thrive & diversify, which produced a range of new species. In the case of the Cretaceous extinction, the demise of the dinosaurs allowed mammals lớn thrive và grow larger.
Scientists refer to the current time as the Anthropocene period, meaning the period of humanity. They warn that, because of human activities such as pollution, overfishing, và the cutting down of forests, the Earth might be on the verge of—or already in—a sixth mass extinction. If that is true, what new life would rise up to fill the nibít that we currently occupy?