NATS 1880 Lecture Notes - Lecture 6: Cambrian Explosion, Clay Minerals, Silicate Minerals
8 Jan 2017
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Chapter 6: origin & evolution of life on earth. Fossils: tell us particular age of fossil/life, but have not discovered the oldest fossils. Stromatolites: living rocks containing layers of sediment & living microbes (upper most microbes use photosynthesis) - giving evidence of existence of microbial colonies as far back as 3. 5 b years & the existence of photosynthetic life. Meaning a simpler form a life (non-photosynthesis) must have existed even earlier! Microfossils: individual fossilized cells (rare) but give evidence of life 3. 4 b years ago. Isotopic evidence: carbon isotope data date rocks back to 3. 85 b years ago. Conclusion: life arose earlier than 3. 85 b years ago. Mapping evolution: dna species comparison determines a timeline of species. Tree of life: species near the root (archaea) are more similar to common ancestor. High-energy radiation: without the ozone layer, radiation would"ve killed organisms on earth"s surface.
