Placeholder Image

Subtitles section Play video

  • Everybody thinks mass extinctions are a bad thing.

  • And for some, yeah, they were literally the worst.

  • But they also show how nature can bounce back.

  • In fact, while extinctions are like a large scale delete button, okay, they're also a way to trigger some new amazing life.

  • A lot of speculation about the evolutionary role of mass extinctions on I think mass extinctions have been really important.

  • I think they played a really major role in opening up ecological opportunities for lineages to diversify and knocking back when it is that have been dominant for long periods of time.

  • The really big mass extinctions are the ones that show up very dramatically in the fossil record.

  • Those air fondly called the Big Five.

  • The Big Five mass extinctions are scattered through the history of life over the last 550 million years and what caused them where things like massive volcanic eruptions, climate changes and even apocalyptic asteroid's.

  • The Big Five accounted for 50% and by some estimates, up to 90% loss of all the species.

  • E think these mass extinctions are important.

  • Evolutionary agents that help shake the system loops and because they open up large amounts of ecological space.

  • They probably do allow for greater evolutionary inventiveness than might have been a potentially possible in a situation of a really crowded world.

  • Mass extinctions basically clear the decks and made room for new life, but it didn't happen overnight.

  • Way we're talking tens of millions of years before we saw life start to make a comeback.

  • But eventually, after this one happened, lots of new fish came to be.

  • And here both plants and reptiles really diversified.

  • Then the first mammals and dinosaurs here, thin after this, tons more dinosaur species.

  • And after the mass extinction that killed off the dinosaurs, there is a new sheriff in town.

  • Terror birds.

  • There's a whole lineage of large carnivorous birds that diversified after the dinosaurs went extinct through the Senate.

  • Select some workers two or 3 ft tall.

  • Some of them were six or 7 ft calls, and so those were pretty spectacular, running around for the landscape, chasing down their mammalian prey.

  • I think luckily for us, they got so dead dinosaurs met new life for them and eventually new life for us.

  • Okay, but seriously, how did anything survive?

  • One of the rules that we find looking at every single mass extinction and many other extinction events.

  • Besides, is that species that are widespread geographically preferentially survived the mass extinction species that are spatially restricted just in one little area, most preferentially go extinct.

  • What it says to me is that what really mattered was having your evolutionary eggs in many different geographical baskets.

  • So what could this mean for humans and future mass extinctions?

  • We don't really know what sort of ciel activities or ahead for the kinds of pressures that were bringing to bear on the ecosystem today.

  • Humans were almost certainly survived in some way.

  • That's because humans have spread nearly everywhere really more the question of the quality of life of those humans and who else will be left behind to occupy the planet with us?

  • And that's really an interesting question.

  • There are plenty of species that we rely on either directly or indirectly that might fall into the high extinction risk category.

  • So understanding mass extinctions and how species recovered can help us a lot.

  • Today.

Everybody thinks mass extinctions are a bad thing.

Subtitles and vocabulary

Operation of videos Adjust the video here to display the subtitles

B1 extinction evolutionary mass extinction life ecological extinct

How Apocalypses Paved the Way for Humans (and terror birds) | Nat Geo Explores

  • 15 1
    林宜悉 posted on 2020/10/24
Video vocabulary