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Warm Little Pond Theory
Uri Miller - simulated early earth environment (methane, ammonia, hydrogen) formed amino acids
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Volcanic Underground Theory (Hydrothermal Theory)
life that can surive in extreme environments, high temperatures, anaerobic, no sunlight, lived off chemicals
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Colonisation Theory
life arrived on a meteorite -ALH84001 - possible microfossils- carbonate globules (found only in organisms) - Mars -stratigraphy and precipitation indicate hydroactivity
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Prokaryotes
first organisms, appeared 3.5 ya, <10 microns, DNA loose in cytoplasm, no nucleus and organelles, reproduce via fission (cloning), have not evolved, no variation
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Eukaryotes
2.5 yo, >10 microns, DNA bound in chromosomes, have nucleus and organelles, reproduction involves recombination, variation
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Endosymbiotic theory- origin of eukaryotes
- One prokaryote partially consumed another - evolves into eukaryote
- Evidence - organelles have their own DNA and 2 membranes
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Earliest known fossils
- Warrawoona, Australia 3.5 Ga - Stromolites - soft bodied, accretionary structure, growth layers single cells tied together
- Common in Pre-Cambrian
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Acritarchs
- 1.8 Ga
- secrete proteinacious cyst
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Ediacaran fauna
Earliest Metazoans (late Pre-Cambrian) - soft bodies not preserved, impressions in sandstone. Similar body structures to later fossils
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Burgess Shale
In BC, Canada - MidCambrian explosion- hard bodies, fossils easily preserved in a low oxygen environment - Shows a rapid diversification of shapes and taxa, some unique to own phyla- first appearance of fauna (Chengjiang has similar fauna)
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Darwin's gradualism
increasing cone of complexity, diversification from one source, slow gradual change (later too much competition for unique new life)
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Punctuated Equilibrium
periods of evolutionary inactivity, then extinction at times of drastic environmental change, rapid biological change
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Decimation and Diversification
high degree of diversity in the past, many forms died out, only few continued to evolve
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