Ch. 25: The Origin of Life on Earth

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What were the atmospheric conditions of the Early earth?
water, carbon dioxide, nitrogen, methane, ammonia, hydrogen, and hydrogen sulfide
What was the 1st stage of the hypothesis for the origin of life on Earth by chemical evolution?
the abiotic synthesis of small organic molecules
What did the abiotic synthesis of small organic molecules include?
amino acids and nitrogenous bases
What was the 2nd stage of the hypothesis for the origin of life on Earth by chemical evolution?
the joining of small molecules into macromolecules
What were the macromolecules that formed in the 2nd stage of the hypothesis of life on Earth by chemical evolution?
proteins and amino acids
What was the 3rd stage of the hypothesis for the origin of life on Earth by chemical evolution?
the packaging of protocells
Protocells
droplets with membranes that maintained internal chemistry different from that of their surrounding
What was the 4th stage of the hypothesis for the origin of life on Earth by chemical evolution?
the origin of self replicating molecules that eventually made inheritance possible
What did Miller and Urey do?
they tested a hypothesis by creating lab conditions comparable to those that existed on early Earth
What did the Miller and Urey experiments yield?
a variety of organic acids found in organisms today, along with other organic compounds
Where did the chemical reactions that Miller and Urey tried to simulate most likely occur?
near volcanoes in early Earth
What was most likely the first genetic material on Earth?
RNA
What evidence is there that RNA was the first genetic material on Earth?
1. RNA can carry out a number of enzyme like catalytic functions
2. There were RNA molecules that carry genetic information and are able to replicate and store information about the vesicles that carried them
Ribozymes
RNA with catalytic function
How do ribozymes work?
they can make complementary pieces of short pieces of RNA, provided they are supplied with nucleotide building blocks
Why does the fossil record provide an incomplete chronicle of evolutionary change? (3)
1. many of Earth's organisms didn't die in the right place at the right time to be preserved
2. some were destroyed by later geological processes
3. only a fraction have actually been discovered
Radiometric Dating is based on
the decay of radioactive isotopes
What happens in Radioactive decay?
a radioactive parent decays to a daughter isotope at a fixed rate
The rate of decay is expressed by a
half life
Half Life
the time required for 50% of the parent isotopes to decay
The first single celled organisms were
bacteria and archaea
What happened during photosynthesis and the oxygen revolution?
gradual rises in oxygen levels were broth about by ancient cyanobacteria
Stromatolites
layered rocks that form when certain prokaryotes bind thin films of sediment together
Put these in order: aerobic metabolism, oxygenic photosynthesis, oxygen, aerobic cells
1. Aerobic Cells
2. Oxygenic Photosynthesis
3. Oxygen
4. Aerobic Metabolism
Endosymbiotic Theory
mitochondria and plastids were formerly small prokaryotes that began living within larger cells
What is evidence for the endosymbiotic theory?
1. Inner membranes of both organelles have enzymes and transport systems homologous to those found in the plasma membrane of living prokaryotes
2. Each organelle contains a single, circular DNA molecule like the chromosomes of bacteria
About how old is Earth?
4.6 Billion Years Old
What were the energy sources to drive reactions in early Earth?
1. Frequent storms with much lightening
2. Frequent volcanic eruptions
3. Frequent meteor impacts
4. UV light from the sun