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Ch 25: History of Life
“There is nothing permanent but change.” (Heraclitus) “Chaos always defeats order because it is better organized.” (Terry
Pratchett)
Louis Pasteur:
Disproving spontaneous generation
Universe forms ~13.8 bya
Early solar system formation ~ 4.5 bya
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Earth’s 1st 1 billion years
Moon formed by a collision
Radiometric Dating
Half-lives 14C: 5,730y 40K: 1.25 by 238U: 4.5 by
Index fossils
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Arrhenius & Mojzsis
organic trace fossils ~3.8 bya
Some of the oldest fossils ~3.4 bya (Strelley Pool, Australia)
http://physicsforme.files.wordpress.com/2011/08/astrobiology3.jpg
JBS Haldane
Abiogenesis: First step- compounds of life from non-living
1920s
AJ Oparin
Harold Urey
Fig 4.2
Miller-Urey experiment (1952/publ 1953)
Stanley Miller 10–15% of the carbon now in the form of organic compounds
2% of the carbon had formed amino acids, with glycine the most abundant (all 20 common ones were found) (In 2008, his student J. Bada reexamined some of the vials.)
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proteinoid microspheres
vesicles
Protobionts
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Thomas Cech
Sidney Altman
Other possibilities for early genetic material: PNAs (Miller)
Which came first?
Where do the materials come from?
Earth
“panspermia”
molecules on space rocks
Note: moves some of the origin question off earth but still have the question…
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Where did life begin?
One hypothesis - deep, hot water
Early microfossils: stromatolites
Shark Bay, Australia (present day)
early O2 production
Banded Iron Formations
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SBMFig. 20.06!
Low
er a
tmos
pher
e!
3(O2)!
2(O3)!U
pper
atm
osph
ere!
Ultr
avio
let r
ays!
Sun!O2 production ->
Ozone (O3) shield protects us from UV
Eukaryotes
-> multicellularity formation of organelles
endosymbiosis
Grypania spiralis (filaments)
Lokiarchaeota discovery 2015 http://phenomena.nationalgeographic.com/2015/05/06/new-loki-microbe-is-closest-relative-to-all-complex-life/
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Current trees of life (largely based on rRNA)
old26.21
26.21
How are organisms related?
Ring of life? (old26.23)
Horizontal gene transfer (26.23)
But may not be a straightforward tree
Snowball Earth
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Tour:
Proterozoic Era: 2.5 bya -> 542 mya
Ediacaran fauna
Paleozoic Era
Cambrian Period 542 -> 488.3 mya all current major animal phyla have appeared
Cambrian Period 542 -> 488.3 mya
Burgess shale fossil animal embryos
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Ordovician Period 488.3 -> 443.7 mya first plants?
Silurian Period 443.7 -> 416 mya
Devonian Period 416 -> 359.2 mya “Age of Fishes”
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Carboniferous Period 359.2 -> 299 mya (large amounts of forest -> major coal deposits)
Permian Period 299 -> 251 mya
Fig. 20.13!
Mesozoic Era “Age of Reptiles”
Triassic Period 251 -> 199.6 mya
Jurassic Period 199.6-> 145.5 mya
Cretaceous Period 145.5 -> 65.5 mya
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Cenozoic Era (Age of Mammals, Insects, Birds, Flowering Plants)
Paleogene Period Paleocene Epoch 65.5 -> 55.8 mya
Eocene Epoch 55.8 -> 33.9 mya
Oligocene Epoch 33.9 -> 23 mya
Cenozoic Era
Neogene Period Miocene Epoch 23 -> 5 mya
Pliocene Epoch 5 mya -> 1.8 mya
Pleistocene Epoch 1.8 mya -> 10,000 ya
Holocene Epoch 10,000 ya -> present? Anthropocene?
Land changes: continental plates and plate tectonics
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“Recent” continental drift
Mass extinctions: 5 – 8 events (note: appear different at different taxonomic levels)
Q: Is one happening now?
Opportunities & changes
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Development changes can change bodies
Timing changes
allometric growth
Development changes can change bodies
Timing changes
paedomorphosis
axolotl
Number of Hox genes
How Hox genes are used
Development changes can change bodies
Changes in genes
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Evolution does not work toward a “goal”
eg: mollusk eyes – all useful
squids & octopi
limpets
Nautilus
snail
snail
Tree of Life video clip with D. Attenborough http://www.wellcometreeoflife.org/video/ Interactive http://www.wellcometreeoflife.org/interactive/