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Lecture

BIOL 111 Lecture Notes - Big Bang, Bipedalism, Ordovician


Department
Biology (Sci)
Course Code
BIOL 111
Professor
Irene Gregory- Eaves

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06/09/12
Origin and evolution of life
1. Origin of life
- life arose once diversify to present
Evolution: genetic alteration and resulting phenotypic change in populations of
organisms occuring across generations
Evolutionary relationships can be tracked through:
- fossil record (changes over time)
- when organisms evolved/environment in which they lived
- morphological comparisons (compare over time and btw organisms)
- evolutionary artifacts (eg human pharynx) enable understanding of
relationships between now and before
- development
- embryotic development patterns allow for comparison
- molectular analysis (DNA)
-Similarities in genome and genetic artifacts
-eg Neanderthal DNA is in human genome = interbreeding
- behavior
Origin theories:
Extraterrestrial source: compounds common inside meteors form building blocks of
life
Chemical evolution:
Miller/Urey (1950) experiment: mimic early atmosphere (CH4, N2, NH3, H2, H2O,
CO2)
- Struck with fake lightning
- Result condensed for analysis
- Found monomers: 4 bases in DNA/RNA
- 17-20 amino acids
- 3- and 6-carbon sugars
- In replicated experiments, sulfur compounds found
- Life necessities:
- monomers join by condensation synthesis reactions requiring energy:
- eg. clay, shores, hydrothermal vents, hot pools polymers
- RNA: pre-DNA
- simpler, catalytic (facilitates replication of through ribosomal action)
- lipids naturally form bilayered spheres
- RNA trapped for more stable environment
- Self-replicating structure nucleic acid inside
2. History of life
If earth’s timeline were a 30 day calendar:
- life arose on the 4th day
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