BIOL 2112 Chapter Notes - Chapter 15: Radiometric Dating, Neoteny, Phanerozoic
4 Jun 2018
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1.Describe the conditions on the surface of the early Earth. Describe the evidence that life on
Earth existed at least 3.5 billion years ago.
The first atmosphere was probably thick with water vapor and various compounds
released by volcanic eruptions, including nitrogen and its oxides, carbon dioxide, methane,
ammonia, hydrogen, and hydrogen sulfide.
Lightning, volcanic activity, and UV radiation were much more intense than today. This
is proven by the fossils in the stromatolites.
2.Describe the four stages that might have produced the first cells on Earth.
1. The abiotic (nonliving) synthesis of small organic molecules such as amino acids and
nitrogenous bases
2. The joining of these small molecules into polymer, such as proteins and nucleic acids
3. The packaging of these molecules into protocells, membrane-enclosed droplets that
maintained an internal chemistry differently from that of their surroundings.
4. The origin of self replacing molecules that eventually made inheritance possible.
3.Describe the experiments of Stanley Miller and others in understanding how life might have
first evolved on Earth.
Miller was testing the Oparin- Haldane hypothesis.
Present day conditions on Earth do not allow the spontaneous synthesis of organic
molecules because the atmosphere is now rich in oxygen which tends to disrupt chemical
bonds.Before the early photosynthetic prokaryotes added O2 in the air, Earth may have had a
reducing (electron adding) atmosphere.The energy for this may have been from UV radiation and
lighting.
4.Describe the significance of protocells and ribozymes in the origin of the first cells.
Protocells- membrane enclosed droplets, formed when lipids mix with water
Ribosomes-help carry out self-replicating processes
5.Describe the key events in the history of life on Earth.
Archaean eon- Prokaryotes formed and changed atmosphere.
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Document Summary
1. describe the conditions on the surface of the early earth. Earth existed at least 3. 5 billion years ago. The first atmosphere was probably thick with water vapor and various compounds released by volcanic eruptions, including nitrogen and its oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide. Lightning, volcanic activity, and uv radiation were much more intense than today. This is proven by the fossils in the stromatolites. 3. describe the experiments of stanley miller and others in understanding how life might have first evolved on earth. 4. describe the significance of protocells and ribozymes in the origin of the first cells. Protocells- membrane enclosed droplets, formed when lipids mix with water. 5. describe the key events in the history of life on earth. Proterozoic eon- towards the end of the archaean eon atmospheric oxygen formed. Then single- celled eukaryotes and then multicellular eukaryotes.
