BIOL 1004 Lecture Notes - Lecture 10: Phylogenetic Tree, Paraphyly

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11 Feb 2016
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Lecture 10 Systematics and Evolutionary Trees
Organizing life
Systematics: scientific discipline focusing on classifying organisms and determining
their evolutionary relationships
Taxonomy: the scientific discipline of concerned with naming and classifying organisms
All groups are formed based on evolutionary relationships. Such as homologies, traits inherited
from common ancestors.
Tetrapod: All species that share the same kind of bones in their arms and legs.
Molecular Homologies: Similarity in the DNA sequences.
Phylogenetic Tree:
Phylogeny: the evolutionary history of a group of organisms
Phylogenetic tree: a branching diagram illustrating an hypothesis about the evolutionary
history of a group of organisms (syn. Cladogram, evolutionary tree)
All trees provide the same basic information: an historical pattern of ancestry, divergence,
and descent
Anatomy of a phylogeny:
Topology: the sequence at which the branch is splitting.
The tips are the living family members.
They are related through common ancestors (the nodes)
Tips are not themselves ancestors of one another
Establishing relatedness:
You establish relatedness in a tree based on the number of shared common ancestors.
Clades:
A common ancestor = all and only its descendant = a clade
Clade = monophyletic group
Doesn’t produce a clade = Paraphyletic group
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