Evolution of Earth Flashcards
What are two theories for the origin of life?
- Abiogenesis
- Panspermia/exogenesis
What is abiogenesis?
- 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
What is panspermia?
Life seeded from outer space on meteors
What are the types of fossils?
- Moulds and casts (of organisms)
- Trace fossils (of footprints and burrows)
- Chemical fossils (chemicals e.g. petroleum)
How are boundaries in the time scale determined?
By events such as mass extinctions
How are layers dated?
- Radiometric dating: radioactive isotopes used to measure geological ages
- Magnetic reversals: Earth’s magnetic field flips and magnetic material in rocks align
What are the ages of Earth’s evolution?
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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)
What happened during the Precambrian?
- 5bya
- First life on Earth
- Origin of prokaryotes and eukaryotes
- Ediacaran fauna: first multicellular organisms
- Did not survive long
What happened during the Cambrian explosion?
- Remarkable change in the fossil record
- Proliferation of shelled fossils
- First sign of most modern animal groups
- Most modern body plans appeared
What caused the Cambrian explosion?
Unclear:
- Increase in oxygen?
- Change in ocean chemistry?
- Predator-prey arms race?
What happened during the Palaeozoic era?
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
What happened during the Mesozoic era?
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?
What happened during the Cenozoic era?
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
What happened with plate tectonics during Earth’s evolution?
- 3bya: supercontinent Vaalbara
- Palaeozoic: Pangaea
- Mesozoic: Laurasia and Gondwana
- Cenozoic: as we know it
What is the Gondwanan legacy?
Fossils and species across continents show they were once joined e.g. Glossopteris across all continents
Why are the ratite birds important?
- Relationships predicted by plate tectonics don’t match DNA analysis
- Tinamou suggests ancestor was able to fly but re-emergence of flight is unlikely
What is biogeography?
The study of the distribution and abundance of organisms based on climatic factors and continental drift
Why is the Wallace Line important?
Asian and Australian flora and fauna are very different and the line corresponds closely to the boundary of tectonic plates
What are biogeographic regions?
Regions inhabited by unique forms of life
What is adaptive radiation?
Organisms diversify rapidly due to a change in environment which leads to new resources, challenges and niches
