4.4. Burgess Shale Experiment

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From the course by University of Illinois at Urbana-Champaign

Emergence of Life

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University of Illinois at Urbana-Champaign

Emergence of Life

56 ratings

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.

From the lesson

Week 4 - Paleozoic Life After the Advent of Skeletons

This week, you'll learn more about the Cambrian Explosion, which led to the development of external hard skeleton components at 542 million years before present. The initial successes of the invertebrates were shortly followed by the appearance of vertebrates with internal skeletons. Life then utilized these newfound evolutionary capabilities, beginning distinct cycles of radiation, diversification, and extinction, which define the three great Eukarya faunas of the Phanerozoic.

4.1. Cycles of Radiation and Extinction7:33

4.2. Cambrian Explosion3:43

4.3. Cambrian Fauna: Origin of Vertebrates14:40

4.4. Burgess Shale Experiment5:38

4.5. Invertebrates: Successes of Life Without a Backbone18:26

4.6. Paleozoic Fauna12:06

4.7. Vertebrates: Successes of Life With a Backbone3:28

4.8. Evolution of Jaws and Perfecting Predation13:15

4.9. Heavily Armored Fish Without Jaws6:44

4.10. Fish Evolution: Hook, Line, and Sinker10:16

Meet the Instructors

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

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The Burgess Shale format is an example another experiment that was run during

the course of evolutionary biology.

Where nature selected for and provided the constraints, and

the environmental setting, and the ecological foundations for

the evolution of a new type of organism.

The Burgess Shale is named after an outcrop of rock that occurs in

the Rocky Mountains of Canada.

And the Burgess Shale itself was deposited in marine environments,

shallow ocean deposits.

They're very fine grained, so it would've been a muddy,

relatively moderately shallow water depth.

And these were organisms that lived on the sea floor and

did very well in this Cambrian time period.

Now, we have an example of another evolutionary experiment that

took place in the, with the Evanachan farm.

And that also did extremely well on a global scale and

then went completely extinct soon after it originated.

This is another example then, and so

the Burgess Shale fauna has provided us with an amazing assortment of organisms.

We see, first of all, crabs that look like some kind of an alien type of life form.

These crabs have these large,

spine-like projections that came around from the head and then it protected

a whole series of segments that made up the body going back into the tail.

So it had all these multiple parts that were moving forward, some of these were

swimmers and some of these were benthic dwellers that lived on the sea floor and

were able to crawl and move forward.

As one example, we had crabs that were part of this assemblage,

and because they are so intricate, we call them a lace crab.

Another completely bizarre organism again we have nothing like this right now,

we call Hallucigenia.

And Hallucigenia looked like a,

maybe a centipede with extremely long legs that had gigantic spikes coming off if it.

And it's appropriately named because you try to describe this to someone and

they'd assume that you were hallucinating.

Again, we have nothing like this on the modern day sea floor,

with all these multiple appendages and legs that allowed them to move forward.

And then this very elaborate system for,

we assume protecting them from predation.

We also had a group of maybe less dramatic organisms but one's,

organisms that lived both on the sea floor and up in the water.

And they again made lifestyle success in ways that we've seen previously

with some of the other organisms that came up in the Cambrian.

But these Burgess Shale are explicitly different from any of the other

ones we saw before.

Another one of the ideas of the Burgess Shale is that we

have a group of predators, that extremely well.

And again that probably, because the predators were so successful,

again help lead to the demise of these organisms.

And one of the major types of predators,

again it's just absolutely bizarre, we call it Opabinia.

And Opabinia looked like some kind of a combination of, If you will.

Some kind of maybe floating crab but then it had a very insect like head and

then coming out from the front of the head it had one long projected

appendage that had a big claw on the front.

And that claw would move the prey that it attacked and devoured into its mouth.

So again, the group of the Burgess Shale is really important.

Now, all the factors that came into playing for the Burgess Shale,

again it's the same group of looking at the origination, radiation and

extinction eventually of organisms.

There were changes in the ecosystem that then began to allow opening of

different parts of the ecosystem to new types of organisms.

These organisms came in quickly, they started evolving and

radiating very successfully and then they'd drop off.

And the drop off was, again, some kind of combination between predation,

environmental change, and other factors that took place in the environment.

The important thing for us is that it's the second example of nature running

a very explicit and specific experiment,

creating organisms that haven't been seen before or seen again.

They were successful for a very short period of time, and

then therefore they went extinct.

The Cambrian fauna includes this group of the Burgess Shale fauna.

And again, towards the end of that time period, as we move from the Cambrian into

the Ordovician and then eventually into the Devonian,

we see that all these faunas dropped off simultaneously.

And they were probably all affected then by the same suite than included biological

pressures on them, competition and predation.

Reproductive strategies, other things that they been evolving and trying to use in

the environment, along with changes in the environment in which they were living.

Like the chemistries that were present, the, ocean water flows,

if there were volcanic events.

If there were ice sheets that were forming and of course,

our old friend the meteor impacts.

Always possible that these would come in randomly at different times,

to reset the stage of evolution, on the sea floor at any given time.

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