Chapter 22 The Origin and History of Life on Earth

Question 1

Hypotheses on the origins of organic molecules typically posit that these molecules originated in the oceans forming what is now called

Answer 1

Prebiotic Soup

Question 2

One hypothesis on the origin of cells proposes the origination of cells from structures which are vesicles surrounded by a lipid layer.

Answer 2

Liposomes

Question 3

One hypothesis on the origin of the diversity of organic macromolecules present on earth today proposes a mechanism similar to natural selection in which the population of molecules changes over time.

Answer 3

Chemical Selection

Question 4

Most scientists propose the origin of life on Earth proceeded through these stages.

Answer 4

1. Organic monomers arise. (Prebiotic soup)
2. Organic polymers arise. (Probiotic soup accumulation of organic molecules.
3. Biochemical pathways for synthesis of organic polymers arise.
4. Cells Arise.

Question 5

Origin of organic Monomers

Answer 5

Reducing atmosphere hypothesis
Extraterrestrial Hypothesis
Deep-sea Vent Hypothesis

Question 6

Reducing Atmosphere hypothesis

Answer 6

Miller and Ury–Demonstrated synthesis of some amino acids, monosaccarides, lipids, and nitrogenous bases from inorganic compounds in a simulation of Early Earth’s atmosphere. c-c-c-c Lightning strike/Primordial ooze.

Question 7

Extraterrestrial Hypothesis

Answer 7

Demonstrated presence of amino acids and nitrogenous bases on meteorites that have landed on Earth. Astrobiology or Exobiology

Question 8

Deep-Sea Vent Hypothesis

Answer 8

Wachterhauser–Demonstrated synthesis of NH3 from N2 at gradient between sea water and materials emitted at hydrothermal vents. Pre-monomer
NH3 necessary for nucleic acids and amino acids.

Question 9

Origin of Organic Polymers

Answer 9

Most likely occured on clay surfaces.
Amino acids will polymerize to polypeptides (short proteins).
Nucleotides will polymerize to nucleic acids.

Question 10

Chemical Evolution

Answer 10

Spontaneous self-assembly of polymers into larger functional units and/or biochemical pathways.

Question 11

Cells Arise

Answer 11

Most likely origin of plasma membrane.

• Liposome
• Structure spontaneously formed by phospholipids in an aqueous environment.
• Experimentally catalyzed on clay.