exam3 - Reasons for similarities Ancestral (primitive)...

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Reasons for similarities Ancestral (primitive) similarity: traits inherited from a common ancestor. Paraphyly Ex: all vertebrates have an internal skeleton - so relationships among verteb- rates to be determined Convergent similarity: structures look similar because of similar functions but they originated independently - can’t determine relationships. Polyphyly Shared derived similarity: single origin. Monophyly Shared: defines the monophyletic group Derived: distinguish group from ancestral form Homology: characteristic shared by two species that were present in their common an- cestor and inherited by both Analogy: characteristic shared by two species that were not present in their common ancestor but rather evolved independently Monophyletic group: ancestor + descendants Paraphyletic group: ancestor + some descendants Polyphyletic group: don’t share recent common ancestor To make a phylogeny Identify derived similarities Use an outgroup- a group known to be ancestral to the group you’re studying Quotes on trees = paraphyletic group Parsimony: tree with fewest # of steps A node on a tree represents a more recent common ancestor Chimps, humans and gorillas- which 2 are more closely related? Use a closely re- lated mammal, like an orangutan as an outgroup. Find a characteristic shared by 2 but not the third- like opposable toes. Since apes have opposable toes, this is probably a primitive similarity of chimps and gorillas that was lost in humans- they’re more closely related Self- replication is the key to life - permits evolution. Mistakes allow some molecules to replicate faster and use energy more efficiently RNA was the first genetic material: contains info to make itself Can evolve to copy itself if given a primer and random mutations - can self-cata- lyze and produce ribozymes RNA store info and can work as an enzyme. Selection can act on RNA directly and change the info content as it acts on the function of the RNA (like replicating). This means that selection can lead to evolution without already requiring special- ized proteins Ribozyme --> other life forms - took a long time Precursor to cell membrane: lipids that can spontaneously form vesicles Viruses Can’t self-replicate - use cell machinery to make a lot of viruses in cell and then burst it, or integrate into host genome and replicate when it does Evidence for nonliving: can’t generate ATP, are acellular, do not reproduce like other living organisms, and lack multi-enzyme systems
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Evidence for living: contain genetic info, can survive and reproduce, info is passed from one generation to the next Prokaryotes: dominant on earth - 10x biomass of eukaryotes. Bacteria and archaea Evolved photosynthesis and aerobic metabolism No nuclear envelope or organelles Circular DNA Paraphyletic - united by primitive similarities Bacterial metabolism: anaerobic
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This note was uploaded on 12/01/2010 for the course BSCI 106 taught by Professor Porter during the Spring '08 term at Maryland.

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exam3 - Reasons for similarities Ancestral (primitive)...

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