Transcript Some thoughts on the origins of life

Winston Churchill
Vioxx
Conspiracy, and dirty little secrets
“Scientific facts” don’t always give us
clear answers to important questions.
Who decides what to do
with “scientific facts”?
What is “life” or “living”
Something that has order ?
What is “life” or “living”
Something that has order ?
What is “life” or “living”
Something that reproduces ?
What is “life” or “living”
Something that reproduces ?
What is “life” or “living”
Something that grows and develops ?
What is “life” or “living”
Something that utilizes energy ?
3Fe + 4H2O <-===->
Fe3O4
+ 4H2
Iron water
iron (II,III) oxide hydrogen
What is “life” or “living”
Something that responds to the environment ?
What is “life” or “living”
Maintains status quo (homeostasis)?
Farmer fixing his fence (life)
vs
Buffered lake (non-living)
Definition of life:
“I can not define it, but I’ll know it when I see it”
-Supreme Court Justice Stewart
Life on Mars?
Life on Mars?
Martian
romantics
Life on Mars? Happy face!
Life on Mars?
Life in extreme Earth environments
A novel thermophile isolated from
>300°C, 1500m deep, geothermal
water pool
Bacillus living at 55°C (131°F)
Life on Mars fossils ?
From Martian meteroite
Bacteria (on Earth)
Size: 1 µm vs 0.1 µm
Are Martian fossils biological ?
Martian
fossils:
-Too small?
-biological?
acid etches
Definition of life:
“I can not define it, but I’ll know it when I see it”
-Supreme Court Justice Stewart
Maybe not so easy after all!
Symptoms of life:
Order, reproduction, growth, development,
energy utilization, response to environment
But what distinguishes “life” from
non-living chemical reactions?
The physical properties of living things
can change, and these changes can be
inherited by offspring
The physical properties of living things
can change, and these changes can be
inherited by offspring
This is possible because the physical properties of “life”
are determined by a program.
This program can be copied, and when it is copied, it can
be changed (mutated)
The physical properties of living things
can change, and these changes can be
inherited by offspring
This is possible because the physical properties of “life”
are determined by a program.
This program can be copied, and when it is copied, it can
be changed (mutated)
Life is unique because it is a
set of chemical reactions that can EVOLVE
So, we know what makes “life” unique
But there are still many questions about how all the diversity
of life came to be…
Life is different from “non-living”
things because life can Evolve
Evolution inevitably results in Natural Selection and
Descent with Modification.
What’s that, and what’s the result?
Natural selection
1. The members of a population have heritable variations.
2. The population produces more offspring than the resources
of an environment can support.
3. There is competition for resources; as a result, the better
adapted individuals survive and reproduce more than the
poorly adapted.
4. Across generations, a larger proportion of the population
becomes adapted to the environment.
Natural Selection leads to
Descent with Modification
Once you have life, and competition for resources,
natural selection will lead a population to change
over time.
Birds. Fig 1.11, page 9
Dogs (artificial selection)
Descent with modification can lead to new species
How much of life’s diversity
can be explained by
descent with modification?
How many different times was life created from
non-life in order to get all this diversity?
All modern life on Earth is related by
descent from a common ancestor
(evolution). Why do we believe this?
Same 4 nucleotides in DNA
Same central dogma
Same 20 amino acids in protein
Because all life is descendent from one original life-form
through an evolutionary process, we can work backward
through time to modern life’s earlier and more simple form.
All life descended from
one common ancestor
Figure 1.4, page 6.
Three main branches (Domains)
When did this occur? And how do they know that?
Stromatolites:
like microfossils of early life
Modern stromatolites
Ancient fossils (?)
How old is the oldest fossil?
Tape measure:
25 feet = 2.5 billion years
1 foot = 0.1 billion = 100 million years
1 inch ~ 10 million years
1/8 of inch ~ 1 million years
width of hair (~1/1000 inch) = 10,000 years
When did all this happen?
And what does it mean?
Earth forms
Carbon isotope (first evidence of life)
First fossil microbes
Oldest eukaryotic fossil
Animal diversity begins
Period of heavy
bombardment
4
dinosaurs
hominids
Oxygen accumulates in atmosphere
3
2
Time - billions of years ago
1
today
When did all this happen?
Geological timeline
Billion years ago
15
4.5
4.0
3.85
2.0
0.5
0.05
0.005
0.0001
0.00001
0.000005
0.0000005
0.00000005
What was happening
universe formed in Big Bang
Earth formed
Heavy bombardment stops
Fossils evidence of life (?)
Fossils of eukaryotes (?)
multi-cellular life becomes abundant
dinosaurs go extinct
chimp/human diverge
firs modern humans
humans colonize Americas (Indians)
ancient Egypt, Greece, Rome, etc
dark ages of Europe
your parents were born
Life started quickly (~200 my), but intelligent life came so late it might
have missed the party all-together (human intelligence arrived after 4 by
of evolution, with only another 1 or 2 by left before all life on Earth ends)