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Lectures 11 & 12: Genome Evolution and History of Life (Similarities…
Lectures 11 & 12: Genome Evolution and History of Life
Earth is 4.5 byo; life is 3.8 byo; eukaryotes evolved 1.5 bya
Cambrian Explosion: 540 mya. Many major groups of animals appeared
Multicelular organisms 800mya
Oxygen
At first little or no free oxygen; then, photosynthetic bacteria appeared 2.5 bya.
Ability to metabolize oxygen 2bya
Large vascular plants further increased Oxygen.
Anaerobes
Aerotolerant Anaerobes: Not damaged by oxygen, but don't use it
Facultative Anaerobes: Can shift metabolism between anaerobic and aerobic
Obligate anaerobes: Can't tolerate oxygen
Aerobes
Obligate Aerobes: need oxygen
All Prokaryotes
Adaptive Radiation: Process by which organisms diversify rapidly from an ancestral species to many new species, following introduction to a novel environment or evolution of a new trait
Large genomes, large gene number likely evolved via drift
Three Domains of Life: Bacteria, Archaea, Eukarya
Similarities among all organisms
Have DNA that encodes proteins
Semi-conservative DNA replication
Have cell membranes and ribosomes
Conduct Glycolysis
Variation among domains
Eukaryotes are only domain to use Sexual reproduction as well as asexual; also have membrane-bound organelles and nucleus
Archaea use methanogenesis
Prokaryotes Use diversity of metabolic pathways
Energy Use
Photoheterotrophs: Light as energy source, carbon from compounds made from other organisms
Chemolithotrophs: Energy from oxidizing inorganic compounds, energy used to fix CO2.
Photoautotrophs: Light as energy source, Carbon from inorganic sources
Chemoheterotrophs: Obtain both energy and carbon from complex organic compounds
Evolution of eukaryotes: Acquisition of eukaryote organelles by endosymbiosis
Happened as environment changed from anaerobic to aerobic
Horizontal gene transfer makes creating lineages more difficult- this can even happen across domains
Evolution of morphological diversity through conserved and novel genes
"Genetic Toolkit" - small changes in highly conserved genes
Novel genes thru gene duplication or orphan genes