Developments & Extinctions of Life on the Geological Time Scale

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  • 0:00 Extinction & Development
  • 0:42 K-T Extinction Event
  • 2:15 Great Permian Extinction
  • 4:08 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Is extinction all that bad? In some ways, it might be. But out of the rubble new developments always arise. This lesson shows you how this is so with a couple examples.

Extinction and Development

As you have aged, things that were once part of you may no longer be there. Yet this has allowed for the development of better stuff.

For example, maybe you used to love to play soccer but no longer do. That may seem kind of sad, but it's actually ok. Because now you have the time and space to play another sport you might like more, like basketball.

As the Earth has aged, it too has had to let go of plants and animals as they have gone extinct. But that's actually ok too. Because the extinction of one group of living creatures gave time and space for the development of others.

Let's see how with a couple of examples.

K-T Extinction Event

Roughly 65-66 million years ago, at the end of the Cretaceous period, a period of the geologic timescale lasting from 145.5 million years ago to 65.5 million years ago, the age of the dinosaurs came to an end.

This is called the K-T Extinction, or Cretaceous-Tertiary Extinction event as well as the K-Pg Extinction, or Cretaceous-Paleogene Extinction event.

What happened? Well, at the tail end of the cretaceous period we know that an asteroid impact occurred at this time.

While some believe the asteroid impact is indeed what killed off basically all of the dinosaurs, others believe it was simply the straw that broke the camel's back, as dinosaurs may have already been in decline well before then as a result of other factors, like climate change.

Either way, the beloved T-Rex, the spectacular flying reptiles called pterosaurs, and other dinosaurs all disappeared from the Earth forever and entered Hollywood lore instead.

The end of the Cretaceous period, however, opened up a whole new world, starting with the Paleogene period. It was one of countless possibilities for birds and mammals to fill the niches left open by the now largely extinct dinosaurs.

Larger, more powerful animals developed on land and in water thereafter. And it was thanks to this slow development in the rise of the mammals that humans were able to evolve.

Great Permian Extinction

While 80% of the world's species of animals died out in the K-Pg extinction event, almost all of life on Earth was killed off in the Great Permian Extinction, an event that killed off over 90% of marine species and at least 70% of land species.

This occurred around 250 million years ago and it's known as the 'Great Dying'. The problem is, no one really has a good grasp of what led to this mass extinction. Some claim it was an asteroid impact, some claim it was crazy volcanism that killed everything off; maybe a nearby supernova, or exploding star, is what did it. We simply don't know for sure what caused the Great Dying.

And although most insects, animals, and plants were wiped out, the Permian-Triassic, P-Tr extinction, as it's otherwise known, led to the restructuring of life forms, ecosystems, and communities.

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