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Course #27615
Anders Gorm PedersenAnders Gorm Pedersen
Molecular Evolution GroupMolecular Evolution Group
Center for Biological Sequence AnalysisCenter for Biological Sequence Analysis
Technical University of DenmarkTechnical University of Denmark
[email protected]@cbs.dtu.dk
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Theory of evolution as the basis of biological understanding
”Nothing in biology makes sense, except in the light of evolution.
Without that light it becomes a pile of sundry facts - some of them interesting or curious but making no meaningful picture as a whole” T. Dobzhansky
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Classification: Linnaeus
Carl LinnaeusCarl Linnaeus1707-17781707-1778
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Classification: Linnaeus
Hierarchical system
KingdomPhylumClassOrderFamilyGenusSpecies
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Classification depicted as a tree
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Classification depicted as a tree
SpeciesSpecies GenusGenus FamilyFamily OrderOrder ClassClass
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Theory of evolution
Charles DarwinCharles Darwin1809-18821809-1882
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Phylogenetic basis of systematics
• LinnaeusLinnaeus: : Ordering principle is God.Ordering principle is God.
• DarwinDarwin: : Ordering principle is shared Ordering principle is shared descent from common ancestors.descent from common ancestors.
• Today, systematics is explicitly Today, systematics is explicitly based on phylogeny.based on phylogeny.
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Darwin’s four postulates
I.I. Each generation more offspring is born than the Each generation more offspring is born than the environment can support - a fraction of offspring environment can support - a fraction of offspring dies without leaving any offspring of its own.dies without leaving any offspring of its own.
II.II. Individuals in a population vary in their Individuals in a population vary in their characteristics.characteristics.
III.III. Some differences among individuals are based on Some differences among individuals are based on genetic differences.genetic differences.
IV.IV. Individuals with favorable characteristics have Individuals with favorable characteristics have higher rates of survival and reproduction.higher rates of survival and reproduction.
Evolution by means of natural selectionEvolution by means of natural selection Presence of ”design-like” features in organisms:Presence of ”design-like” features in organisms:
quite often features are there “for a reason”quite often features are there “for a reason”
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Theory of evolution as the basis of biological understanding
““Phylogenies, or evolutionary trees, are the basic Phylogenies, or evolutionary trees, are the basic structures necessary to think clearly about the differences structures necessary to think clearly about the differences between species, and to analyze those differences between species, and to analyze those differences statistically.”statistically.”
Joseph FelsensteinJoseph Felsenstein
