7.1. House of the Rising Mammals

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來自 University of Illinois at Urbana-Champaign 的課程

Emergence of Life

57 個評分

University of Illinois at Urbana-Champaign

Emergence of Life

57 個評分

How did life emerge on Earth? How have life and Earth co-evolved through geological time? Is life elsewhere in the universe? Take a look through the 4-billion-year history of life on Earth through the lens of the modern Tree of Life! This course will evaluate the entire history of life on Earth within the context of our cutting-edge understanding of the Tree of Life. This includes the pioneering work of Professor Carl Woese on the University of Illinois Urbana-Champaign campus which revolutionized our understanding with a new "Tree of Life." Other themes include: -Reconnaissance of ancient primordial life before the first cell evolved -The entire ~4-billion-year development of single- and multi-celled life through the lens of the Tree of Life -The influence of Earth system processes (meteor impacts, volcanoes, ice sheets) on shaping and structuring the Tree of Life This synthesis emphasizes the universality of the emergence of life as a prelude for the search for extraterrestrial life.

從本節課中

Week 7 - Cenozoic Mammals and Global Environmental Change

With the demise of the dinosaurs, mammals rapidly radiated and diversified during the Cenozoic. The combination of abundant food sources and significant fluctuations in global climate fostered extreme variations in morphology, body size, and interaction with the environment. You'll learn why mammals had a distinct advantage over previous groups, and you'll also have the opportunity to explore multiple theories on primate and hominoid evolution in the context of global conditions during this period.

7.1. House of the Rising Mammals4:54

7.2. Mammals Conquer the Earth7:31

7.3. Big is Beautiful6:05

7.4. Sophistication of Mammal Skulls8:16

7.5. Mammalian Dentition: My, What Big Teeth You Have!11:25

7.6. Mammals: Taxonomy is in the Eye of the Beholder12:19

7.7. Mammal-Marsupial Exchange: There Goes the Neighborhood7:56

7.8. The Primates11:38

7.9. The Rise of Humans: Getting a Leg Up on the Competition9:37

7.10. Early Hominids: Trees versus Savannahs8:17

與講師見面

Bruce W. Fouke, Ph.D.
Director of the Roy J. Carver Biotechnology Center
Department of Geology, Department of Microbiology, and Institute for Genomic Biology

[SOUND]

[MUSIC]

I'm Bruce Fouke from the University of Illinois Urbana-Champaign.

The rise of the mammals wasn't just coincidence.

It was an Earth that was ready to have a new breed, a new type of very diverse,

sophisticated, and capable set of organisms evolve and

radiate into new Earth eco-space that was opened up

dramatically by the KT Impact at 65.5 million years before present.

So, let's look at the history from the KT Impact to the modern

as a broad brush overview of what the earth was like at that time period.

The place to start that I think is really, really important here is

the idea that the earth was extremely warm in the age of the dinosaurs.

So as you can see in this diagram at the left-hand side,

you'll see the vertical axis, the y axis is temperature, and

the x axis is time, that the average temperatures of the Earth at the time of

the dinosaurs were approaching 26 to 29 degrees celsius.

Now that is fully another 10

to 15 degrees celsius warmer than what it is in the modern day earth.

So, the average temperature of the modern day earth is approximately 14 degrees

celsius.

So the earth was a very warm place.

And one of the things to keep in mind when you take a look at the concepts of

a modern day warming earth, it's not the question of magnitude or how much warming

is taking place because we've had an Earth that was a lot warmer than it is now.

And we've had an earth that was a lot colder.

We had ice sheets even at the equators.

So it's not the magnitude or

the amount of warming, it's the rate over which the warming is taking place.

And I think that's really well emphasized by taking a look at a graphic like this of

how warm the Earth used to be, especially in the age of the dinosaurs.

Well coming off the KT Impact, the Earth cooled a little bit, but not much.

Went back up and hit another high at the end of the Paleogene, and

then the Earth started a dramatic history of cooling, which we are still a part of.

And you can see, then, the rapid drop in temperature as we move into the Eocene.

Now, the Eocene is marked by another fundamentally critical event in Earth's

history, and that was the rise and the development of the Antarctic ice sheet.

So from the age of the dinosaurs in the Cretaceous through the Eocene,

it was a planet without ice sheets, and

then the Earth cooled again to the point where ice could be developed on the poles.

So the Antarctic,

the onset of Antarctic glaciation in the Eocene, nicely shown on this diagram.

And from that Eocene time period, then we've seen an Earth where the relative

rates of some of the warming or cooling have increased, but

not nearly as rapidly as what we're seeing in the modern day Earth.

Over the last 100 years the average rise in

Earth temperature has been about 1 degree Celsius.

But from about 2000 up until 2100, the estimates are that the rise in

Earth's temperature could be as great as 8 degrees Celsius over 100 years.

And 8 degrees Celcius is dramatically steeper and faster than any of

the types of temperature rises or drops that we see on these diagrams.

Was we go from the Eocene now were into a glacially dominated earth.

We have rises and falls, rises and falls, with an overall drop in temperature,

especially after we reach the end of the Oligacene and into the Miocene.

And so those drops continue until we get into the age of the ice, or

the Ice Ages in the Pleistocene.

So on the lower right-hand part of this diagram, you'll see we move into

the glacial episodes with high frequency, in a relative sense, change in

temperature, but nothing even close to what we're recording in modern-day Earth.

So this is the template we need to remember,

an incredibly warmer Earth at the age of the dinosaurs.

The KT Impact opening up ecosystem space, both in the terrestrial and

marine environments, and then a slow trend toward cooling,

then the onset of the Antarctic glacial sheets.

And then moving fully into the age of the ice.

So we are now coming out of the most recent cold time period on

planet Earth and then tracking the advance and

the acceleration of warming as we move up into the modern.

So this template of a warm earth that's cooling,

that's going into then a high frequency changing earth of temperature

is a template over which especially the mammals have evolved.

And that would be the stage on which we'll evaluate mammalian evolution throughout

the Cenozoic.

[MUSIC]

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