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Origin and Diversity of Life

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Biology (Sci)
BIOL 111
Irene Gregory- Eaves

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 (CH , N , N4 , 2 , H3O, 2 2 CO 2 - 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 4 day 06/09/12 - recorded humans arose during the last 5 minutes of 30 dayth Timeline: 4.5 bya: earth forms 3.8 bya: origin of life 2.5 bya: photosynthesis 1.5 bya: eukaryotic life 700 mya: multicellular life 542 mya: Cambrian explosion 420 mya: life on land 200000 ya: humans Physical changes: - Continental drift - Oceanic changes, sea level changes - Volcanic activity, meteorite collisions - Change in temp - Increase in O2 - no O2 to start, bacterial mutations to photosynthesize  Energy from light splits 2 O, reduces CO 2ith O a2 waste - allow evolution of aerobic respiration - cyanobacteria, photosynthetic prokaryotes form stromatotlites Precambrian (largely unicellular): 4.5bya -life confined to oceans -unicell
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