CH 25.1: Origin of Life on Earth

Question 1

What is the four stage hypothesis?

Answer 1

1. abiotic synthesis of small organic molecules (monomers)
2. linking of monomers into polymers
3. formation of “protobionts” or vessicles ( protection for polymers)
4. self-replication

Question 2

What is the Miller-Urey experiment?

Answer 2

tested the hypothesis that organic molecules were abiotically synthesized under atmospheric conditions or the primordial Earth (results: amino acids were produced)

Question 3

What are protobionts?

Answer 3

the first formed cells or the aggregate of abiotically produced organis molecules surrounded by membranes

Question 4

Why is RNA an autocatalyst?

Answer 4

because it can accomplish any biochemical reaction by itself without any additional requirements

Question 5

What is the evidence that life may have in association with deep-sea hydrothermal vents?

Answer 5

molecular data suggests that ancestors of modern prokaryotes were thermophilic, may have oxidized organic sulfur compounds as an energy source, and precursors of organic compounds used in metabolism are abiotically produced in association with hydrothermal vents

Question 6

What does sedimentary strata tell us?

Answer 6

gives relative ages of fossils (used for really old fossils that can’t be determined by radio-carbon dating)

Question 7

How does Radio-carbon dating work?

Answer 7

dating relies on the rate of decay of a “parent” isotope to a “daughter” isotope. The ratio of C14:C12 gives the age of a fossil. Can be used to date fossils up to about 62,000 y/o.

Question 8

What are stromatolites?

Answer 8

fossilized remnants of bacterial colonies that indicate early life

Question 9

What is the Serial Endosymbiosis model?

Answer 9

the prokaryotic ancestors of mitochondria and plastids probably gained entry to the host cell as undigested prey or internal parasites

Question 10

What is the evidence that supports the endosymbiotic model?

Answer 10

1. Enzymes and transport systems of organelle membranes are similar to prokaryotes
2. Replication by splitting (binary fission)
3. Circular DNA, with an absence of histones
4. Passes independent cellular machinery to transcribe their DNA into proteins
5. Ribosomes of mitochondria and chloroplasts are more similar to prokaryotic ribosomes than sytoplasmic ribosomes of eukaryotis cells

Question 11

What was life prior to the Cambrian era?

Answer 11

referred to as Ediacaran and the fauna was mainly soft organisms which didn’t leave many fossils

Question 12

What was the Cambrian Explosion?

Answer 12

refers to the “sudden” appearance of fossils resembling modern phyla in the Cambrian period and provides the first evidence of predator-prey interactions