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.
4.6. Paleozoic Fauna
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From the course by University of Illinois at Urbana-Champaign
Emergence of Life
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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.
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 second great fauna that we have seen arise in the geological record as a result
of evolutionary biology experiments through time is called
the Paleozoic Fauna.
The Paleozoic fauna replaced and came on board after the Cambrian fauna.
It originated, it started really doing fairly well in the Ordovician, and
there was overlap between the end of the Cambrian fauna and
then the beginning of the Paleozoic fauna and the reason for
that overlap is some of the organisms are very similar.
They're in the same group of sea floor organisms.
That were invertebrates, the corals and the bivalves and
the trilobites all these organisms were coexisting at the same time.
But then the Cambrian fauna we saw
a replacement of some of these with other related organisms.
So the Paleozoic fauna rose in the Ordovician and then really zenith and
did extremely well through the run of the Dovonian.
The Mississippian, and the Pennsylvanian time periods going into the Permian.
And, they continue doing well,
until a natural disaster took place at the end of the Permian.
A major meteor hit the planet, caused about 85% of everything living,
in both the oceans and on land, to go extinct.
And that 85% drop then in the diversity of life on the planet
is shown in the fossil record.
And, again, remember kind of the invisible guiding hand behind the structure of how
we understand geological time to have been parsed out through the millenia.
Is the idea that a lot of geological time in the Phanerozoic
is based on the radiation and then extinction of fossils.
So, the Paleozoic fauna is the second of the great faunas, and
we're going to see that there were organisms that were familiar to us and
organisms that were not.
One of the advents of the Paleozoic fauna is the idea that plants actually began to
take hold and radiate and evolve on the land's surface.
So, we had some plants in the oceans, algae and other forms of plants.
But then, especially in the Ordovician, we see the first example of plants leaving
the seawater environment and going into the terrestrial land environment.
So we got a small foothold in the Ordovician], and
some of these early plants they were very simple in their structure.
They had a very rudimentary root system, and
the root system actually gave them stability and the ability to pump water.
And move water and actually hold water, because
moving from the ocean into the land means that you're able to store water and
carry it with you so you don't dehydrate.
And another thing that happens is you're able to
solve the riddle of how to reproduce without water.
When you're in water, reproduction
has lower hurdles of difficulty than if you live in the land environment.
There's multiple things, the ability to gain food,
and other types of nutrient sources.
But the invasion of the land happened with the plants,
that marked the beginning of the Paleozoic fauna.
Now, some of these early plants, they looked a lot like ferns, or
they looked almost like, in a small types of tropical trees, that we can think of.
They had various shapes, but they were very bushy and fern like.
And they started to colonize this land environment.
Now in terms of the geological response to this colonization,
we saw that river systems, before we had plants,
rivers could just flow and meander and cut through landscapes unconstrained.
They was just based on how much water there was and
the ability to cut into mobile landscape.
As soon as plants came aboard, we saw fundamentally that the ability of
river systems to erode is constrained by plants.
We see all the time in the modern day environment,
plants living along the edge or river systems and on lobbies and
those plant root systems bind the soil and they actually attenuate and
control and determine some of the erosion that goes on.
So the whole dynamic of eroding a natural landscape
was altered by the invasion of the land plants.
Now, another thing that is accompanied in the Paleozoic
with the advent of the land plants is that provides a major source of food.
So we see that a gigantic food source became available and
of course the way that nature responds, the way evolutionary biology
responds to a new food source is new things evolve to eat that food source.
So, the land plants provided food and then we had another
major explosion in the organisms that could live on land as well as in the sea.
So, everything changed.
Now at that same time period then as we were having the evolution
of the fish in the seawater,
then we started having fish that develop capabilities to come on land, and
we'll be seeing this evolution from fish then eventually into amphibians, the ones
that can live both in and out of the water, and eventually into the reptiles.
We'll see how the great radiation of the three groupings of reptiles,
one of which we've evolved from, all came about because of the proliferation
of the food source in these land based environments.
Now, [COUGH] one of the things that we need to remember is,
globally, every place has fossils.
Every country on the planet has got fossils.
And every country on the planet has got a template or a basic sweet of
basic rock types that everyone runs around on and everyone ignores on a daily basis.
But, something that's really important to recognize in the course of evolutionary
biology is that these great discoveries have happened all over the planet.
And when these discoveries take place it is very common for people to name
the fossils after the geographic locations in which the fossils were found.
And we'll see this occurring over and over through time.
Well, in this Paleozoic fauna,
as we had this whole succession of fish into amphibians, into reptiles,
and, then the land plants blossomed, we also had the emergence of the insects.
And some of the insects that we know of, the dragonflies, and the butterflies,
flies themselves, all kinds of organisms, that are very, very diverse.
All did very well in that Paleozoic fauna.
And again, it's all related directly to the relationship of the insects to
the diversification of the different types of plants.
And one of the most striking fossil assemblages we have on planet Earth for
this time period actually takes place here in the state of Illinois.
And we have a very unique kind of fossil that we find, and
indeed it's the state fossil.
Every country, every state, every place, depending on what fossils
are abundant there, they name one of those fossils a state or a country fossil.
The state of Illinois,
the fossil here is called a Tully Monster, and a Tully monster.
It looks something like a segmented worm
that has some jaws on the end with a mouth.
And it's very bizarre looking because it had a very small mouth and
jaw system and then it had a very long neck.
And then it kind of inflated out to be a segmented worm like central body
that had a bit of a flipper on the end.
So, the Tully Monster is a weirdo, but it's extremely common in the state
of Illinois and the reason it's common is that during the Paleozoic,
one of the time periods of that is called the Pennsylvanian and
when you're in Europe and other places the Mississippian and
Pennsylvanian are combined into a time period called the Carboniferous.
And the Carboniferous is the great age of the coals.
And so, the Carboniferous in Europe was split into two divisions.
The earlier one is called Mississippian and
the later one is called the Pennsylvanian here in the United States.
And so this great time period of the age of coals, the coals were formed from
having incredibly well developed forests that grew out into marshy areas.
And it was also a time period of having the oceans be relatively high because
we had little to no ice on the planet.
So all the ice that's normal bound up in the oceans,
release back into the water and sea level becomes very high.
So all the conditions were right to have a lot of organic matter deposited quickly
along the margins of the oceans and especially in deltaic systems and marsh
systems that were right on the borderline between the coastal regions of the world.
These very thick coal deposits were very important at the time period.
And in coal swamps you have a suite of environmental constraints that are just
right to preserve very fragile organisms if they die and fall to the water.
And these waters are very low in oxygen and because they're
low then they have a unique suite of microbes that live in the waters.
And then you have the ability to have very high rates of sedimentation,
very quick burial of something that dies and falls into the water.
So the coal swamps are a great place to make fossils.
The Tully monster is an example of that.
The Tully monsters lived in these coal swamps and when they died and
their bodies hit the bottom of the swamp before they could be eaten by
something else it wasn't uncommon for them to be buried very quickly.
And they were buried in environments where the oxygen levels were very low and
it allowed to have this very unique, beautiful,
perfect preservation of the organism.
Now, another reason that it gets preserved is in these swampy, muddy environments and
as the organisms dies it's tissue breaks down and releases different chemicals.
And some of these are organic acids, and some of them,
there's just a whole suite of different chemicals that come out and
those chemicals radiate away from the body concentrically.
So they start at the body that's decaying and then moves out.
And so we see these chemical reactions that go from
where the actual organism has died and is in the sediments, and moves out away.
And those chemical reactions actually make the sediments,
transition chemically into becoming a solid rock.
And so the solid rocks that we have that preserve these, we call them Concretions.
They look like small eggs but they're kind of flattened and so
these flattened egg-like structures are very common in coal swamp
areas around the world, and again, especially here in the state of Illinois.
If you take those concretions and you put them outside in the wintertime and
then put them outside in the summertime, let them heat up to high temperatures
naturally in the summer, freeze down the cool temperatures in the winter.
They're actually naturally crack open and the crack open along that flat part
of the flattened egg, and it pops into two pieces, and you open it up, and
inside is a beautifully preserved organism.
One of them is the Tully monster.
But everything that lived in the coal swamps
were also preserved in this fashion.
So the concretions have given us a fantastic fossil record of butterflies,
where individual patterns and beautiful shapes of the scales on the leaves,
they're all perfectly preserved down to a single cell level.
We have plant material that looks like it was growing yesterday.
Perfectly preserved in this.
And another great example is the Tully monster.
So, the Paleozoic was diversification at a level that the planet hadn't seen before.
It involved not only the invertebrates, but
then the simultaneous evolution of the vertebrates.
And it included great success in marine environments,
but then full on invasion of the terrestrial land environments.
And those are the characteristics of the Paleozoic fauna.
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