Age of earth and solar system

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Age of earth and solar system.4.5-4.6 bya
(radioisotopic dating of meteorites)
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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)
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How do we define life? What steps do you need to
get evolution of life?
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• What steps do you need to get evolution of life?
  P459
• Small organic molecules (like amino acids)
• Joining of these into longer macromolecules (like
  proteins, nucleic acids)
• A packaging of some sort
• Origin of self replication

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• Small Organic Molecules like amino acids?
• Miller and Urey

Hydrogen methane and ammonia
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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!
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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 seventh-grade school dance
into a raging molecular mosh pit.http//discoverma
gazine.com/2008/feb/
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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
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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
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So what evidence do we see for early life?
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Oldest fossils of Prokaryotes Stromatolites
p440 Similar to Cyanobacteria (3.5bya) Relatives
still exist in Western Australia
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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..
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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.scien
cedaily.com/releases/2006/07/060721090947.htm
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• 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

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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
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What else do we know? We do find large spherical
organic molecules called fullerenes at meteor
impact sites. Bacteria can survive outer
space!
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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 light-years away,
and that its parent star is visible to the naked
eye. Its 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-much-for-ear
th-being-special-there-could-be-20-billion-just-li
ke-it/ixzz2mKVgqMRv
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Figure 23.10
1,100
1,000
25
900
800
20
700
600
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Total extinction rate (families per million
years)
Number of families
500
400
10
300
200
5
100
0
0
Paleozoic
Mesozoic
Cenozoic
Era Period
Q
E
O
S
D
C
P
Tr
J
P
C
N
542
488
444
416
359
299
251
200
145
65.5
0
Time (mya)
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Precambrian before about 500mya Prokaryotes Eukary
otes-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
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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)
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Paleozoic Period about 500-250mya Climate-Moist
Swampy Plants-ferns, mosses, horsetail Giant
insects
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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)
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Many Diverse Synapsids (p 441 mentioned)
A dicynodont
Thrinaxodon-cynodont
nationalgeographic.com
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More Synapsids
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Figure 23.4a
Reptiles (including dinosaurs and birds)
OTHER TETRAPODS
Dimetrodon
Synapsids
Very late (non-mammalian)cynodonts
Therapsids
Cynodonts
Mammals
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Figure 23.10
1,100
1,000
25
900
800
20
700
600
15
Total extinction rate (families per million
years)
Number of families
500
400
10
300
200
5
100
0
0
Paleozoic
Mesozoic
Cenozoic
Era Period
Q
E
O
S
D
C
P
Tr
J
P
C
N
542
488
444
416
359
299
251
200
145
65.5
0
Time (mya)
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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/feature
4/
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• Mesozoic about 250-65mya
• Since Pangaea had formedDRY
• Plants-conifers
• Dinos super diverse! Mammals around..
• Flying and pollinating insects begin to diversify
  with flowering plants

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Pterosaurs Plesiosaurs Ichthyosaurs Dinosaurs
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Figure 23.10
Cretaceous Extinction event (K/T)!
1,100
1,000
25
900
800
20
700
600
15
Total extinction rate (families per million
years)
Number of families
500
400
10
300
200
5
100
0
0
Paleozoic
Mesozoic
Cenozoic
Era Period
Q
E
O
S
D
C
P
Tr
J
P
C
N
542
488
444
416
359
299
251
200
145
65.5
0
Time (mya)
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7 miles across
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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
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• 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 camels back
  (dinos were in decline before the impact)

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Cenozoic -65mya to present Spreading apart of
continents.. Flowering plant diversity
accelerates Insects continue dramatic
diversification Mammals diversify
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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!
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Rememberthere 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

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• 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

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Species Average Lifespan years (MYA) All
Invertebrates Raup (1978) 11 Marine
Invertebrates Valentine (1970) 510 Marine
Animals Raup (1991) 4 Marine Animals
Sepkoski (1992) 5 All Fossil Groups Simpson
(1952) .55 Mammals Martin (1993)
1 Cenozoic Mammals Raup and Stanley (1978)
12 Diatoms Van Valen 8 Dinoflagellates
Van Valen (1973) 13 Planktonic Foraminifera
Van Valen (1973) 7 Cenozoic Bivalves Raup and
Stanley (1978) 10 Echinoderms Durham (1970)
6 Silurian Graptolites Rickards (1977)
2 Adapted from the book extinction rates,
edited by Lawton, J, and May, R.8 Wikipedia!!
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Figure 23.10
How long did it take for diversity to recover
after Permian extinction event? ESTIMATE!!!
1,100
1,000
25
900
800
20
700
600
15
Total extinction rate (families per million
years)
Number of families
500
400
10
300
200
5
100
0
0
Paleozoic
Mesozoic
Cenozoic
Era Period
Q
E
O
S
D
C
P
Tr
J
P
C
N
542
488
444
416
359
299
251
200
145
65.5
0
Time (mya)
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www.geol.umd.edu/.../lectures/natresources.html
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