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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/