Origin of Life (overview )
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Transcript of Origin of Life (overview )
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Origin of Life (overview)1. Chemical evolution2. Replicators- RNA or DNA?3. Individuality: Protocells --> cells4. Prokaryotes: Earliest true cells (~3.5 bya)5. Endomembrane system: Increase in
cellular complexity6. Endosymbiosis: Further increase in
eukaryote complexity and expansion of biochemistry
7. Multicellularity: Cooperative grouping of differentiated, clonally related cells
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Logic of Origin of Life
1. Diverse environment2. Lots of Time --> perhaps hundreds of
millions of years3. Non-oxidizing atmosphere --> without
lots of O2 around, organic molecules are much more stable
4. Organic molecule stability without O2 allowed life to evolve slowly from nonliving material
5. Organic Molecules
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Logic of Origin of Life1. Energy - volcanoes, deep-sea vents,
lightning, sun light, chemicals from space
2. natural selection:
• Stuff that is durable and easily made tends to accumulate
• Chemicals that are stable, and can duplicate themselves, naturally increase in abundance
3. Little Early Competition
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Oparin’s hypothesisEarly Earth needed
•Water vapor
•Carbon dioxide
•Methane
•Nitrogen
•ammonia
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Miller & Urey Experiment (1953)
Miller and Urey
devised the experiment
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Extraterrestrial Energy Sources
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Terrestrial Energy Sources
oceanic geothermal
vents (underwater geysers and hot springs)
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Laboratory Protobionts
Shown is some degree of abiotic individuality
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Relative Vs Absolute Dating
Relative dating:• Geological time scales• Relative position in
rock strata• Index fossils- trilobites Absolute dating:• Actual “clock”• E.g., radioactive decay
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Radiocarbon Dating
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The Carbon 14 Dating Process
1 atom of C14 for every 1013 C12 atoms in the atmosphere
Once an organism dies, the C14 is trapped and decays. Half-life is about 5800 years
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1. Bacteria and Archea diverge- 2-3 bya2. Photosynthetic bacteria produce
oxygen- 2.5 bya3. Eukaryotes emerge- 2 bya4. Plants emerged from green algae ~700
mya5. Fungi and animals emerge from uni-
cells ~ 700 mya 6. First terrestrials- 450 mya
Geologic Record
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Permian (250 million years ago): 90% of marine animals; Pangea merge
Cretaceous (65 million years ago): death of dinosaurs, 50% of marine species; low angle comet or meteor ( ~10 km across)
Mass Extinction
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Snowball Earth (latest ~650 mya)
Severe ice ages covered the entire planet
Multicellular organisms survived deep in oceanic thermal vents and clustered together for protection
Meteor impact could cause another
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