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Lecture 18

BIOL 1F90 Lecture 18: BIOL 1F90 lecture 18 winter 2016


Department
Biological Sciences
Course Code
BIOL 1F90
Professor
Fiona Hunter
Lecture
18

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Friday, February 12, 2016
BIOL 1F90
Lecture 18
Phylogenetic Trees
-phylogeny: evolutionary history of a species or group of species
-to propose a phylogeny, biologists use the tools of systematics
-trees are usually based on morphological or genetic data
-diagram that describes phylogeny
-a hypothesis of evolutionary relationships among various species
-based on available information
-new species can be formed by
-anagenesis: single species evolves into a dierent species
-cladogenesis: a species diverges into two or more species
-monophyletic group or clade
-group of species, taxon, consisting of the mose recent common ancestor and all of its
descendants
-smaller and more recent clades are nested within larger clades that have older common
ancestors
-for larger taxa, common ancestor existed a log time ago (kingdom)
-for smaller taxa, common ancestor more recent (family or genus)
-paraphyletic group
-contains a common ancestor and some, but not all, of its descendants
-over time taxonomic groups will be reorganized so only monophyletic groups are
recognized
-reptiles were a paraphyletic group because birds were excluded
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