Evolution of Earth

Question 1

What are two theories for the origin of life?

Answer 1

• Abiogenesis

- Panspermia/exogenesis

Question 2

What is abiogenesis?

Answer 2

• The primordial soup
• Energy input from hydrothermal vents/electrical storms
• The Urey-Miller experiment: produced amino acids required for life using products found on early Earth

Question 3

What is panspermia?

Answer 3

Life seeded from outer space on meteors

Question 4

What are the types of fossils?

Answer 4

• Moulds and casts (of organisms)
• Trace fossils (of footprints and burrows)
• Chemical fossils (chemicals e.g. petroleum)

Question 5

How are boundaries in the time scale determined?

Answer 5

By events such as mass extinctions

Question 6

How are layers dated?

Answer 6

• Radiometric dating: radioactive isotopes used to measure geological ages
• Magnetic reversals: Earth’s magnetic field flips and magnetic material in rocks align

Question 7

What are the ages of Earth’s evolution?

Answer 7

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Precambrian (4.5bya):
- Cambrian explosion
Palaeozoic (545mya):
- Cambrian
- Ordovician
- Silurian
- Devonian
- Carboniferous
- Permian
Mesozoic (250mya):
- Triassic
- Jurassic
- Cretaceous
Cenozoic (65mya):
- Paleogene
- Neogene
- Quaternary: Pleistocene, Holocene (200,000ya)

Question 8

What happened during the Precambrian?

Answer 8

4. 5bya
   - First life on Earth
   - Origin of prokaryotes and eukaryotes
   - Ediacaran fauna: first multicellular organisms
   - Did not survive long

Question 9

What happened during the Cambrian explosion?

Answer 9

• Remarkable change in the fossil record
• Proliferation of shelled fossils
• First sign of most modern animal groups
• Most modern body plans appeared

Question 10

What caused the Cambrian explosion?

Answer 10

Unclear:

• Increase in oxygen?
• Change in ocean chemistry?
• Predator-prey arms race?

Question 11

What happened during the Palaeozoic era?

Answer 11

545mya
Cambrian
Ordovician, Silurian, Devonian:
- Rise in diversity of marine life
- First fish and amphibians evolve
- Devonian: age of fishes
Carboniferous:
- Plants colonised the land and insects diversified
- Amphibians on land
- First reptiles
- Atmosphere had high oxygen
- Fossil fuels formed
Permian:
- At the end of the permian a massive extinction even occurred
- 96% of all marine species went extinct

Question 12

What happened during the Mesozoic era?

Answer 12

250mya
Triassic:
- First dinosaurs and mammals
Jurassic:
- Age of the reptiles: flying and marine
- Cycads and conifers
- First birds
Cretaceous:
- First flowering plants which diversified and replaces a lot of earlier vegetation: mosses, ferns, gymnosperms
- Ended with massive extinction event: asteroid impact/volcanic activity?

Question 13

What happened during the Cenozoic era?

Answer 13

65mya
Paleogene, Neogene:
- Radiation of flowering plants and mammals

Quaternary:
Pleistocene:
- Climatic events that shaped flora and fauna
- Mega fauna
- Ice ages
Holocene:
- Humans expanded in range

Question 14

What happened with plate tectonics during Earth’s evolution?

Answer 14

• 3bya: supercontinent Vaalbara
• Palaeozoic: Pangaea
• Mesozoic: Laurasia and Gondwana
• Cenozoic: as we know it

Question 15

What is the Gondwanan legacy?

Answer 15

Fossils and species across continents show they were once joined e.g. Glossopteris across all continents

Question 16

Why are the ratite birds important?

Answer 16

• Relationships predicted by plate tectonics don’t match DNA analysis
• Tinamou suggests ancestor was able to fly but re-emergence of flight is unlikely

Question 17

What is biogeography?

Answer 17

The study of the distribution and abundance of organisms based on climatic factors and continental drift

Question 18

Why is the Wallace Line important?

Answer 18

Asian and Australian flora and fauna are very different and the line corresponds closely to the boundary of tectonic plates

Question 19

What are biogeographic regions?

Answer 19

Regions inhabited by unique forms of life

Question 20

What is adaptive radiation?

Answer 20

Organisms diversify rapidly due to a change in environment which leads to new resources, challenges and niches