Chapter 25. Phylogeny & Systematics - Explore...
Transcript of Chapter 25. Phylogeny & Systematics - Explore...
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Chapter 25.Phylogeny & Systematics
An unexpected family tree. What are theevolutionary relationships among ahuman, a mushroom, and a tulip?Molecular systematics has revealedthat—despite appearances—animals,including humans, and fungi, such asmushrooms, are more closely related toeach other than either are to plants.
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Phylogeny & Systematics Phylogeny
evolutionary history of a species based on common ancestries inferred
from fossil record morphological & biochemical resemblances molecular evidence
Systematics connects classification
system to phylogeny bycategorizing & namingorganisms
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5000 year old ice mummy found on an Alpineridge dividing Austria from Italy at 10,500 feetabove sea level.
Fossil record Sedimentary rock are richest source of
fossils fossil record is a substantial, but
incomplete, chronicle of evolutionaryhistory spotty historical documents of biology
history of life of Earthis punctuated bymass extinctions
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Paleontology Study of fossils
fossils provide the strongestevidence of change
links past & current organismsWoolly mammoth tusks
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Fossils
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Building phylogenies Morphological & molecular homologies
similarities based on shared ancestries bone structure DNA sequences
beware of analogous structures convergent evolution
marsupial mole
placental mole
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Evaluating molecular homologies Aligning DNA
sequences more bases in
common =more closelyrelated
analyzed bysoftware
beware of molecular homologies
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Systematics Connecting
classification tophylogeny hierarchical system Linnaean system binomial system
genus species
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Connectionbetweenclassification& phylogeny
Tracing possible evolutionaryrelationships between someof the taxa of the orderCarnivora, a branch of theclass Mammalia.
Building trees
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Illustrating phylogeny Cladograms
patterns of shared characteristics
Classify organismsaccording to theorder in time atwhich branchesarise along aphylogenetic tree
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Molecular Systematics Hypothesizing phylogenies using molecular
data apply principle of parsimony
simplest explanation fewest evolutionary events
hypothetical birdspecies
3 possiblephylogenies
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Parsimony Choose the “tree” that explains the
data invoking the fewest number ofevolutionary events
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Parsimony & analogy vs. homology
Phylogenetic trees are hypothesesWhich is the most parsimonious tree?
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Modern Systematics Shaking up some trees!
Crocodiles arenow thought tobe closer tobirds thanother reptiles
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Of Mice and Men… Evolving genomes
now that we can compare the entiregenomes of different organisms, we find… humans & mice have 99% of their genes in
common 50% of human genes have a close match with
those of yeast the simplest eukaryote
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Molecular clocksTrace variationsin genomes todate evolutionarychanges
Rate of change iscalculated andthen extrapolateback
What does thisassume?
HIV-1M samples were collected frompatients between early 1980s & late1990s. The gene evolved at a relativelyconstant rate. Concluded that HIV-1Mstrain first infected humans in 1930s.
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Universal Tree of Life 3 Domains
Bacteria Eukarya Archaea