Age of earth and solar system….4.5-4.6 bya
(radioisotopic dating of meteorites)
Early impacts were colossal
A Mars sized chunk hit earth and dislodged a chunk
of earth that became the moon
Some solid crust by about 4 bya
(some rocks in Canada are 3.96 billion years old).
Surface water by about 3.8 bya
(sedimentary rocks of that age in Greenland)
How do we define life?
What steps do you need to get evolution of life?
What steps do you need to get evolution of life? P459
1. Small organic molecules (like amino acids)
2. Joining of these into longer macromolecules (like
proteins, nucleic acids)
3. A packaging of some sort
4. Origin of self replication
1. Small Organic Molecules like amino acids?
Miller and Urey
Hydrogen methane and ammonia
2. Assembly of these building blocks into
polymers
Now we need to get them together into proteins and
nucleic acids
Drip solutions onto hot rocks evaporation borders
encourage polymerization (hooking together)
or Ice!
Miller and Bada
As an ice crystal forms, it stays pure: Only
molecules of water join the growing crystal, while
impurities like salt or cyanide are excluded.
These impurities become crowded in microscopic
pockets of liquid within the ice, and this crowding
causes the molecules to collide more often.
Chemically speaking, it transforms a tepid seventhgrade school dance into a raging molecular mosh
pit.http://discovermagazine.com/2008/feb/
3. Packaging-Acquire cellular form
We know now that membranes often form
spontaneously under certain circumstances-vesicles
Hydrophobic molecules in a mixture organize into a
bilayer at the surface of droplets like the lipid
bilayer of a plasma membranes
This will control entry and exit from the “cell”
4. Origin of self replicating polymers
RNA world
Important in protein synthesis but also can take on
enzyme like functions.
DNA probably evolved later as a safe depository
for genetic info-more stable
So what evidence do we see for early life?
Oldest fossils of Prokaryotes
Stromatolites p440
Similar to Cyanobacteria (3.5bya)
Relatives still exist in Western Australia
Chemical fingerprints-Carbon Isotope
(Harrison, Manning and Mojzis)
Remember those sedimentary rocks in Greenland
(3.85)..
Those rocks have been heated and squished so
unlikely to see fossils but…
Look at carbon isotope ratios and can detect
presence of life..
“The carbon aggregates in the rocks have a ratio of
about 100-to-one of 12C (the most common isotope
form of carbon, containing six protons and six neutrons)
to 13C (a rarer isotopic form of carbon, containing six
protons and seven neutrons). The light carbon, 12C, is
more than 3 percent more abundant than scientists would
expect to find if life were not present, and 3 percent is
very significant……..”
http://www.sciencedaily.com/releases/2006/07/060721090947.htm
Where??
Surface ponds-Primordial soup-Surface dangerous!
Why?
Deep sea vents- Interesting amino acids form there
“The worst impacts would have been 10-100 million
years apart and a handful of hardy bacterial souls
could have survived at the bottom of the
oceans….”
Science News December 2000
Other planets?
Panspermia hypothesis…
Europa (moon of JUPITER) water and active
volcanoes -hydrothermal vents in liquid ocean
capped by ice??
Mars-today is cold and dry but had liquid water
and it may have had an atmosphere that warmed
it…
What else do we know?
We do find large spherical organic molecules called
fullerenes at meteor impact sites.
Bacteria can survive outer space!
Last fall…. (Time Magazine description of article in
PLOS)
That adds up to about 20 billion Earths in our galaxy
alone, says lead author Erik Petigura, of the
University of California, Berkeley. That in turn means
that an Earth-like world is likely to be just 12 lightyears away, and that its parent star is visible to the
naked eye. “It’s really amazing when you think about
it,” Petigura says.
Read more: 20 Billion Earths in the Milky Way Alone? | TIME.com http://science.time.com/2013/11/04/so-muchfor-earth-being-special-there-could-be-20-billion-just-like-it/#ixzz2mKVgqMRv
Figure 23.10
1,100
1,000
900
800
20
700
600
15
500
400
10
300
200
5
100
0
Era
Period
E
542
Mesozoic
Paleozoic
O
S
488 444 416
D
C
359
P
299 251
Tr
J
200
Time (mya)
C
145
0
N Q
0
Cenozoic
P
65.5
Number of families:
Total extinction rate
(families per million years):
25
Precambrian before about 500mya
Prokaryotes
Eukaryotes-1.8bya is fossil date for evolution of
multicellularity but is some evidence for
much earlier
Cambrian explosion
Paleozoic
End Permian Extinction
Mesozoic
Cretaceous Extinction
Cenozoic
Cambrian explosion about 500mya (550mya)
Nearly all major “styles” or body plans of animals
appear!
Major evidence is from Burgess Shale in B.C.
CANADA (also from China and Greenland)
Are earlier fossils of animals but are soft and
squishy (see Fig 25.2 p483 bottom right
Ediacaran)
Paleozoic Period about 500-250mya
Climate-Moist Swampy
Plants-ferns, mosses, horsetail
Giant insects
Many diverse amphibians were large! 9ft
And scary fish
Science Daily
Tiktaalik roseae, an early
tetrapodomorph (late Devonian period,
~380 M. y. ago) (Credit: Arthur Weasley,
GNU Free Documentation licence)
Many Diverse Synapsids
(p 441 mentioned)
A dicynodont
Thrinaxodon-cynodont
nationalgeographic.com
More Synapsids
Figure 23.4a
Reptiles
(including
dinosaurs and birds)
†Dimetrodon
Cynodonts
Therapsids
Synapsids
OTHER
TETRAPODS
†Very late (nonmammalian)
cynodonts
Mammals
Figure 23.10
1,100
1,000
900
800
20
700
600
15
500
400
10
300
200
5
100
0
Era
Period
E
542
Mesozoic
Paleozoic
O
S
488 444 416
D
C
359
P
299 251
Tr
J
200
Time (mya)
C
145
0
N Q
0
Cenozoic
P
65.5
Number of families:
Total extinction rate
(families per million years):
25
End Permian-250mya
Effect 90-96% of all species
Who Extinct?
Synapsids, many Amphibians!
Giant insects-dragonflies,
cockroaches
Horsetail trees, Tree ferns (some)
Why?
Huge amounts of lava oozing out of
the earth Siberia
Formation of Pangaea
Mixing of oceans slows-anoxic
http://www.nationalgeographic.com/ngm/
0009/feature4/
Mesozoic about 250-65mya
•Since Pangaea had formed===DRY
•Plants-conifers…
•Dinos super diverse! Mammals around..
•Flying and pollinating insects begin to diversify
with flowering plants
Pterosaurs
Plesiosaurs
Ichthyosaurs
Dinosaurs
Cretaceous Extinction event (K/T)!
Figure 23.10
1,100
1,000
900
800
20
700
600
15
500
400
10
300
200
5
100
0
Era
Period
E
542
Mesozoic
Paleozoic
O
S
488 444 416
D
C
359
P
299 251
Tr
J
200
Time (mya)
C
145
0
N Q
0
Cenozoic
P
65.5
Number of families:
Total extinction rate
(families per million years):
25
7 miles across…
Cretaceous (K/T)
Effect 50% of all species
Who? Dinosaurs, Pterosaurs, Plesiosaurs, many
small marine species
On land nothing bigger than 25 kgs survived-all
survivors were small
Why? Impact
There is debate about the precise role of the impact
on Dinosaur Extinctions..
Opinions range from….
•Impact was the cause
•Impact was one of the causes
•Impact was the straw that broke the camel’s back
(dinos were in decline before the impact)
Cenozoic -65mya to present
Spreading apart of continents..
Flowering plant diversity accelerates
Insects continue dramatic diversification
Mammals diversify
More Mass Extinction…
Catastrophism
So.. Although classic “Darwinian” slow adaptive
evolution is important….
we now appreciate the role of catastrophic events
(chance events) in the evolution of the diverse forms
of life on the planet!
Remember…there is a creative side.. Extinctions
open up new space for “adaptive radiations”
•Ex. Mammals after Cretaceous extinction
event
•Ex. Dinos diversified after End-permian
extinction when Synapsids extinct
The species alive today are only a tiny fraction of
all those that have ever lived.
•The vast majority of all species in the history of
the planet have gone extinct.
•So extinction is normal
•Average lifespan of a species from its origin to its
extinction is between 1 and 5 million years
Species Average Lifespan years (MYA)
All Invertebrates
Raup (1978)
Marine Invertebrates
Valentine (1970)
Marine Animals
Raup (1991)
Marine Animals
Sepkoski (1992)
All Fossil Groups Simpson (1952)
Mammals
Martin (1993)
Cenozoic Mammals Raup and Stanley (1978)
Diatoms
Van Valen
Dinoflagellates
Van Valen (1973)
Planktonic Foraminifera Van Valen (1973)
Cenozoic Bivalves Raup and Stanley (1978)
Echinoderms
Durham (1970)
Silurian Graptolites Rickards (1977)
11
5–10
4
5
.5–5
1
1–2
8
13
7
10
6
2
Adapted from the book “extinction rates”, edited by Lawton, J,
and May, R.[8] Wikipedia!!
How long did it take for diversity to recover after
Permian extinction event? ESTIMATE!!!
Figure 23.10
1,100
1,000
900
800
20
700
600
15
500
400
10
300
200
5
100
0
Era
Period
E
542
Mesozoic
Paleozoic
O
S
488 444 416
D
C
359
P
299 251
Tr
J
200
Time (mya)
C
145
0
N Q
0
Cenozoic
P
65.5
Number of families:
Total extinction rate
(families per million years):
25
www.geol.umd.edu/.../lectures/natresources.html