Origin of Life

004b

When space turned around, the earth heatedWhen space turned over, the sky reversed

When the sun appeared standing in shadowsTo cause light to make bright the moon,

When the Pleiades are small eyes in the night,From the source in the slime was the earth formedFrom the source in the dark was darkness formed

From the source in the night was night formedFrom the depths of the darkness, darkness so deep

Darkness of day, darkness of nightOf night alone

Did night give birthBorn was Kumulipo in the night, a maleBorn was Po'ele in the night, a female

Born the coral polyp

Born of him a coral colony emerged....

pp. 3-4, Johnson, R.K., 1981. The Kumulipo: Hawaiian hymm of creation. Vol. 1. TopgallantPublishing Co., Ltd., Honolulu, Hawai'i

• Universe formed 15 billion years ago (Big

Bang)

• Galaxies formed from stars, dust and gas

• Earth formed 4.6 billion years ago

Earth 3.5 bya

• Suns energy stripped away 1st atmosphere

• 2nd atmosphere formed from volcanic outgassing

• Primitive atmosphere: CO2, water vapor, lesser

amts of CO, N2, H2, HCl, and traces of NH3 and

CH4 (3.5 bya)

• O2 came in 3.2-2 bya

• Autotrophic Organisms: photosynthesis

• Another environmental change

• Result in evolution

Earth’s Atmosphere

OxygenEvidence for O2 production:

Banded Iron Formations (BIF) BIF found in ocean sediments red

bands are high in Fe2O3 and Fe3O4 (red bands)- forms when reduced iron reacts with O2

“Oxygen revolution”

Time (billions of years ago)

4 3 2 1 0

1,000

100

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0.001

Oxygen

Evolution of Ozone• Accumulation of free O2 in the atm also led to

the accumulation of ozone– Ozone important for blocking incoming UV

radiation

• Even small amounts of atm O2 leads to enough ozone to provide some protection against UV– Partial screen likely to have formed ~ 1.9 bybp– Presence of this UV filter allowed life to move out

of the oceans and onto land– Consistent with the timing of evolution of

eukaryotes and higher plants

• 0.5 billion years ago

• Atmosphere O2 to 1% current

• Compare to present: 78% N2, 21% O2, 0.04% CO2, + trace gasses

• Relatively small, most single cell

• Start of multicellularity

• Increase in cell complexity

Formation of Earth’s Oceans(4 bybp):

Rain

Condensation

Off gassing of water vapor from volcano

Life began~ 3.5 bya

Organic molecules (C H O N P S) swimming in shallow seas

Stage 1: Abiotic synthesis of organic molecules such as proteins, amino acids and nucleotides

Stage 2: joining of small molecules (monomers) into large molecules

Stage 3: origin of self-replicating molecules that eventually made inheritance possible

Stage 4: packaging these molecules into pre-cells, droplets of molecules with membranes that maintained an internal chemistry

Thomas Huxley- Search for origin of life

Wyville Thompson: HMS Challenger (1872-1876) found it was actually diatomacous ooze reacting with seawater and ethyl alcohol

Bathybias heckali- primordial ooze

Miller and Urey’s Experiment

ELECTRICITY!!!

Organic molecules like amino acids

Produced:• 20 amino acids• Several sugars• Lipids• Purine and pyrimidine bases (found in

DNA, RNA & ATP)

RNA worldRNA world

• The first genetic material was probably self-replicating, catalytic RNA not DNA;

• In “RNA world”, RNA could have provided the template on which DNA was assembled

• Once DNA appeared “RNA world” gave way to “DNA world”

• The first organisms were not photosynthetic; they were probably heterotrophic

Protobionts, collections of abiotically produced molecules surrounded by a membrane-like structures

Liposomes can form when lipids or other organic molecules are added to water.

- Have a bilayer- Can undergo osmosis- Can “reproduce”

Protocell (Protobiont)Fatty acid membrane with ribozymes inside

OxygenEarliest Evidences: oldest fossilsOldest photosynthetic microbes 3.5-3.2 B.Y.

- Bacterium-like- Unicellular- Evidence for breakdown products of photosynthesis

Cyanobacteria, 3.5 B.Y.

Stomatolites, 3.5- 0.7 B.Y.

Three-domain systemExtremophilesProkaryotes Eukaryotes

Look at how this evolution happened!

chemosynthetic bacteria (extremophiles)

Chemosynthesis:

02 + 4H2S + C02 CH20 + 4S +3H20

Stromatolites (bacteria & cyanobacteria)

Oldest fossils found in western Australia and southern Africa ~ 3.5 byo

Photosynthesis:

6H2O + 6CO2 + nutrients + light energy C6H12O6 + 6O2

Stromatolites from Shark’s Bay Australia

mostly cyano

Early prokaryotes may have arisen near hydrothermal vents

Hydrothermal vents are rich in sulphur and iron-containing compounds needed for ATP synthesis. Temperatures can reach 120 C.

Hot springs in Yellowstone National Park – pigmented bacterial mats

1st dinosaur

end of dinosaurs

1st reptiles1st amphibians

1st land plants1st fish

1st invertebrates

Millions of YearsGeologic Time Scale

Extinctions• Habitat Disruption

– Volcanic Eruptions– Asteroid Impacts– Sea Level Change

• Habitat Modification– Climate Change– Mountain-Building– Sea Level Change– Precipitation Change– Toxic Materials

• “Exotic” Species Introductions– Continental Drift

The Big Five

• Ordovician-Silurian extinction - 439 million years ago, 60% extinct

• Late Devonian extinction - 364 million years ago, 70% extinct

• Permian-Triassic extinction - 251 million years ago, 90% extinct

• End Triassic extinction, - 199 million to 214 million years ago, 44% extinct

• Cretaceous-Tertiary extinction, about 65 million years ago, 85% extinct

Life during Ordovician488-443 mya

Graptolites, trilobites, conodonts, algae, fish, coral, crinoids, gastropods

All known metazoan life confined to the seas and oceans

The Ordovician Extinction Event

• 450 Ma - 440 Ma, two bursts of extinction occurred, separated by one million years

• > 60% of marine invertebrates died;

• Gondwana moves south

• Sea level falls

• Atmospheric CO2 drops

• Global cooling

Middle Ordovician

Life in Devonian416-359 mya

The Devonian Period

• 416-359 mya• Pangeae forms• Extensive reef building• Age of Fishes• Plants & insects colonize land• First vertebrates colonize land

The Devonian Extinction Event

• Possibly two to as many as seven related bursts of extinction centered on 365 Ma to 440 Ma, over as little as one half to as many as 25 million years

• Marine life most affected

• Jawed vertebrates unaffected by the loss of reefs, while agnathans in decline.

The Devonian Extinction Event

• Leading theories include changes in sea level and ocean anoxia, possibly triggered by global cooling or oceanic volcanism

• The widespread oceanic anoxia prohibited decay and allowed the preservation of sedimented organic matter as petroleum

Late Devonian / Early Carboniferous

Life in Permian290-245 mya

The Permian Period• 290-245 mya• The south was cold and arid.• Northern areas suffered

increasingly from intense heat and great seasonal fluctuations between wet and dry conditions.

• Dinosaurs dominate.

The Permian Period• The Earth's most severe mass extinction

event, – 96% of all marine species – 70% of terrestrial vertebrate species – mass extinction of insects– Some 57% of all families and 83% of all genera

were killed

• recovery of life on Earth took significantly longer than other extinction events

The Permian Extinction Event

• There were from one to three distinct pulses of extinction that occurred about 245-251 million years ago

• Several proposed mechanisms for the extinctions:– earlier phase - gradual environmental

change– latter phase - catastrophic event

The Permian Extinction Event• Suggested mechanisms for the latter

extinction pulse include: – large or multiple bolide (meteor/comet) impact

events– increased volcanism and sudden release of

methane clathrate from the sea floor– gradual changes include sea-level change,

anoxia, increasing aridity, and a shift in ocean circulation driven by climate change

– Excess CO2 acidified oceans, contributing to the decline of shelled organisms

The Permian Extinction Event

Late Permian

The Triassic Period250-200mya

The Triassic Period• Low oxygen levels• New respiratory systems developed:

air sacs and diaphragms• Early Triassic- high CO2 & CH4

• Many land reptiles returned to the sea

• 80% of the land was arid or semiarid• Late Triassic- Pangea breaks up

The Triassic Extinction Event• The extinction occurred around 208

million years ago and happened in less than 10,000 years just before Pangaea started to break apart

• This extinctions struck marine life and terrestrial life profoundly

• At least 50% of the species now known to have been living at that time went extinct

• In the seas, a whole class (conodonts) and 20% of all marine families disappeared– Conodonts were early eel-like chordates

The Triassic Extinction Event• On land, all large crurotarsans (non-dinosaurian

archosaurs) other than crocodilians, some remaining therapsids, and many of the large amphibians were wiped out

• This event vacated terrestrial ecological niches, allowing the dinosaurs to assume the dominant roles in the Jurassic period

The Triassic Extinction Event• Several explanations for this event have been

suggested, but all have unanswered challenges:

–Gradual climate change or sea-level fluctuations

–Asteroid impact

–Massive volcanic eruptions

Late Triassic / Early Jurassic

Late Cretaceous Extinction Event

• a relatively rapid extinction event dated to 65.5 million years

• K–T boundary

• a thin band of iridium-rich sedimentation found in various parts of the world

Late Cretaceous Extinction Event• The event marks the end of the Mesozoic Era and the

beginning of the Cenozoic Era• Essentially all non-avian dinosaurs, mosasaurs,

plesiosaurs, pterosaurs and many species of plants and invertebrates became extinct

• Once dinos gone, mammals dominate in next period

The Late Cretaceous Extinction Event

• The Chicxulub impact, a 10km diameter meteorite, leaving a crater ~200 Km in diameter

Impact caused acid rain, ash that blocked out the sun for months, severe global cooling (nuclear winter). Increase in atmospheric CO2, resulting in global warming, final blow to dinosaurs & many other Cretaceous species.

The Late Cretaceous Extinction Event

• Other possibility: increased volcanic activity (India’s Deccan Traps)

The Deccan basalt traps of India were then antipodal to the Chicxulub impact

What Happened to the Dinosaurs?

The Late Cretaceous Extinction Event

• Before the end of the Cretaceous, flight evolved independently three times:– Insects, flying reptiles, birds (avian dinosaurs)

• By the end of the Cretaceous 65 Mya, most dinosaurs along with other large marine reptiles and various invertebrates died out

• No land vertebrate larger than a large dog survived the KT boundary event

• The angiosperm radiation was well underway during the Cretaceous, but the shift from gymnosperm to angiosperm dominated forests may have been triggered by the Late Cretaceous Extinction

Late Cretaceous

6th Major Extinction

Golden toad1989

Yangtze River dolphin 2006

Stellar’s sea cow1768 Tasmanian Tiger

1936Quagga1883

Passenger PigeonMartha 1914

Hawaiian Honey Creepers

Kauai O'O (extinct); Kauai Akialoa (extinct); Kauai O'u (extinct) ; Kauai Nukupu'u (extinct); Puaioho (less than 200 left); Kamao (extinct)

Hawaiian Monk Seal

Not Extinct

California Condor

Sea otterGreen Turtle