2.3. Revolution of the Tree of Life

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En provenance du cours de University of Illinois at Urbana-Champaign

Emergence of Life

60 notes

University of Illinois at Urbana-Champaign

Emergence of Life

60 notes

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.

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Week 2 - The Tree of Life and Early Earth Environments

The advent of life on Earth came about as a result of a remarkable confluence of physical, chemical, and biological processes, all of which were intrinsically linked to rapidly changing early Earth environments. Within this context, cutting-edge approaches in molecular phylogeny by Professor Carl Woese revealed new understandings of the emergence of life and the possible distribution of life within the cosmos. All this and more will be explored in this week's lessons!

2.1. The Scientific Inquiry of Carl Woese8:00

2.2. The Place of Carl Woese in Evolutionary Biology8:24

2.3. Revolution of the Tree of Life7:41

2.4. Evolution of the Tree of Life6:42

2.5. How Did Life Emerge?5:25

2.6. The Genetic Code and Evolutionary Theory7:23

2.7. Throwing Rocks at Earth: The Martian Meteorite10:46

2.8. Microbial Mats and Stromatolites: Laying Down On the Job6:49

2.9. Oxygenation of the Atmosphere5:15

2.10. Snowball Earth; It Did Freeze Over!8:31

Rencontrer les enseignants

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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My name is Jan Sapp.

I'm a professor in the history of biology at York University in Toronto.

And I write about the history and philosophy of biology.

So Woese thought, writes a book in 1967 called The Genetic Code.

But it's very unusual book, because that book was embedded in evolutionary biology.

It was all about how the code evolved.

Molecular biologists ignored evolution.

Molecular biologists weren't concerned with evolution.

Molecular biology turned into primarily an engineering discipline.

What can we do with this stuff?

It was just sort of something we had to know about the secret of life.

But it itself didn't want to understand it's own evolution.

Thought it was off, to speculate about the origin of life was merely that,

it was speculation.

Let's get serious and do real science.

>> That was around the time I said to myself, this is biology,

you study biology, you have to study evolution.

And so I set up the system.

It could do it, it was the first system that could do it.

That was the oligonucleotide cataloging.

>> Well, Wells wanted to do that with respect to the origins of the genetic

code, to say well how can I study the genetic code without speculation.

How can I have an empirical study of the evolution of the translation apparatus?

So his answer was, well if I can make a deep phylogeny, that is,

if I can order simple organisms, say bacteria and

eukaryotes, back to some ancient

forms perhaps I'll find organisms, that have a different apparatus and

then I can order them in terms of the way in which the translation evolved.

So he starts to do that and he picks a molecule that is part of the ribosome.

The ribosome's at the heart of the translation machine.

He thought it was all organisms that we know have ribosomes, organisms and

not viruses, but other, all organisms that have DNA and RNA and

that have both have DNA and RNA and that can synthesize proteins have ribosomes so

use a universal characteristic is an essential characteristic just like

Darwin's essential characteristic,

just like Lamarck's essential characteristic's even though he

broadsided the field knew nothing about the classical evolutionary biology.

So he begins to work on ribosomal RNAs with the idea that, if he could

look at the sequences, and in those days you could have very short sequences up to

about 13 nucleic acid units base pairs, right?

So the first thing he did was let's see what what sequences within these RNAs and

these ribosomes are universal to all bacteria, for example.

And so he finds patterns that all bacteria have,

find other patterns that all eukaryotes have.

The idea of molecular evolution was that it was a clock, and

this was the clock that Linus Pauling and

Emile Zuckerkandl published in 1965, that the genetic code, or nucleic acids,

information molecules, will change like a clock, as a steady beat like that.

And that is to do with random mutations, it's neutral,

selection doesn't act on that.

It's like a car with the engine going before you put it into gear.

And you're going to have lots of variations before you actually change

the and evolution will only see that That's the theory.

So through studying the pattern of these changes in the nucleic acids,

in information molecules, whether they'd be amino acids or nucleic acids,

one is studying in part as a clock, as a evolutionary clock.

Woese thought, that the RNA molecule was the ultimate,

the universal chronology.

Well, when he arrives at the University of Illinois in 1964

the program of microfiber genetics gets up certainly by the late sixties.

He has about 15 years where nobody knows really what he's doing.

By 1990 everything breaks because Woese makes a formal proposal.

A formal proposal.

The evolution is tolerated.

Because before he's sort of invisible.

Okay everybody knew there was this guy that was cranky.

Making all these remarks about what they take to be iconic concepts in evolutionary

biology, pretending now that he can order life through one molecule.

And he teamed up with really, he didn't have much support in the United States.

Great support in Germany, with Otto Canner and Wolfram Zillig and Karl Statta.

And these are really important for the story.

But in 1990, fast forward in 1990,

when they make the formal taxonomic proposal there are three domains.

The archae bacteria he wants to redefine now as the archaea.

And the reason he did that is that genomics, full blown genomics comes about.

Human genome project emerges by 1990,

around that time, that one could now sequence all the genes in an organism.

This is amazing.

This is amazing.

Well, Woese and Gary Olsen here at University of Illinois put on a proposal

to sequence I think it was an archaebacteria and

they were turned down on the grounds that they all ready had a sequence of e

coli [LAUGHS] And one didn't need to sequence any more of these things.

You've seen one you've seen them all.

I mean, that was the attitude about bacteria.

They're all the same aren't they, I mean gimme a break.

It was the old joke there's two kinds of bacteria,

E coli and the other one,

and that was basically the view of things, especially from the part of.

You say come on, these things are all the same,

Woese wants to analyze these things in terms of molecules, this is absurd.

You can't compare the difference between bacterium and and archain, and

compare that distinction to a kangaroo and a giant sequoia, it's absurd

to think that that's a distinction, you know, that would make a new domain.

So, Woese made three higher uuu, proposed three higher above the kingdoms.

So, the argument was, there'd be three fundamental domains,

three fundamental lineages of life.

The eukaria, the bacteria and the archaea.

And the reason he called them the archaea was because he didn't want the word

bacteria associated with them for

the reason of people thought that all bacteria were the same.

So, it set up a biopolitical argument.

He called them domains, because he didn't want militaristic concepts in biology.

Before, we were in the Middle Ages.

It was all kingdoms,

and we still use these Middle Age kind of expresses kingdoms of nature, you know?

What does that mean and why are we still living in kingdom's?

I mean, you know, we're in democracies now, we don't need royalty.

I mean, who are these people?

But we still have these noble kingdoms, pretty bizarre, right?

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