Ch15. The Origin Of Life

Question 1

4 main stages of the origin of life

Answer 1

1. Synthesis of small organic molecules
2. Joining of small molecules into macromolecules
3. Origin of self-replicating molecules
4. Assembly of protocells

Question 2

Stage 1

Answer 2

Nucleotides and amino acids were produced prior to the existence of cells
- spontaneous soup
- prebiotic soup

Question 3

reducing atmosphere hypothesis

Answer 3

early atmosphere
- water vapor, nitrogen, carbon dioxide, hydrogen gas, ammonia
the atmosphere was a reducing environment
others suggest the environment was neutral

Question 4

Miller Urey experiment

Answer 4

Electrodes passed sparks through heated gasses, which cooled into liquids before another round of heating. The process generated organic compounds, including amino acids.
-Proved that the conditions that existed on primitive Earth were capable of leading to organic compounds
- chemicals used: Water, H2, CH4 and NH3 gases, UV Rays and electricity

Question 5

Deep sea vent hypothesis

Answer 5

Cracks in the earth’s surface: superheated water rich in metal ions and hydrogen sulfide mixes with cold seawater.
Organic molecules may have been formed in a temperature gradient.

Question 6

Stage 2

Answer 6

Simple molecules polymerize to form RNA
- RNA synthesis can occur spontaneously
- organic molecules formed on the surface of clay

Question 7

stage 3

Answer 7

Origin of self-replicating molecules
- RNA first macromolecule
- Ribosomes

Question 8

RNA (first macromolecule)

Answer 8

1. store information
2. capacity for self-replication
3. perform enzymic functions
4. It is more versatile than DNA

Question 9

Ribosomes

Answer 9

act as a catalyst to synthesize macromolecules
- can make copies of short pieces of RNA

Question 10

RNA evolution

Answer 10

1. RNA performs two roles – DNA takes over the information storage
2. RNA can serve as a template to make DNA
3. Proteins have greater catalytic ability than RNA
4. RNA can catalyze peptide bond formation

Question 11

Stage 4

Answer 11

polymers enclosed by a boundary

protocells

Question 12

Protocells

Answer 12

• Cluster of molecules surrounded by a boundary
• Chemically separate from the environment
  -ex: coacervates, liposomes
  1. boundary
  2. information
  3. enzymic function
  4. self-replication

Question 13

History of life on Earth

Answer 13

4.55 billion years ago (6,000ish years)
- Genetic Changes of Evolution
- Environmental Changes

Question 14

Geological time scale

Answer 14

4 eons
- phanerozoic
- proterozoic
- archaean
- Hadean
eras (phnaerozoic eon)
- cenozoic
- mesozoic
- paleozoic

precambrian vs cambrian

Question 15

Prokaryotes (first cell)

Answer 15

1.8 billion years ago
endosymbiosis theory

Question 16

Oxygen boom (2)

Answer 16

-little oxygen at first
-began with little photosynthesizers
-evolution of cellular respiration

Question 17

Evolution of Mitochondria and Chloroplasts

Answer 17

-Enveloped by a double membrane
-Contain free ribosomes and circular DNA molecules
-Grow and reproduce somewhat independentlyin cells
-Replicate by a splitting process similar to prokaryotes

Question 18

Endosymbiosis Theory

Answer 18

some ancient organisms engulfed bacterial cells. rather than digesting them as food, the host cells kept them on as partners in mitochondria and chloroplasts

Question 19

Cambrian explosion

Answer 19

535-525 million years ago
marine invertebrates, arthropods, vertebrates, rising oxygen levels

Question 20

Diversification?

Answer 20

-hard shell in marine species to find new habitats
-increase oxygen levels
-an arms race between predator and prey

Question 21

Triassic and cretaceous period

Answer 21

-first mammals and dinosaurs appear
-reptiles are dominant land animals

Question 22

first hominins

Answer 22

-Sahelanthropus tchadensis dated between 6 and 7 mya
-Australopithecus afarensis “Lucy” about 3.85 and 2.95 mya
-Modern Homo sapiens about 170,000 years ago

Question 23

Consequences of Continental Drift

Answer 23

Formation of the supercontinent Pangaea about 250 million years ago had many effects
- A deepening of ocean basins
- A reduction in shallow water habitat
- A colder and drier climate inland