Transcript Nov 27 - University of San Diego

I.
Phylogeny and Systematics
A.
Cladistics
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Analysis of phylogenetic relationships based
on shared characters
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Characters may be primitive or derived
Clade = Group of species that includes
ancestral species and all descendents
Cladogram – Diagram that illustrates
evolutionary relationships among clades
Outgroup – Used to distinguish primitive from
derived characters
I.
Phylogeny and Systematics
B.
Relationships among Taxa
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Taxa may be categorized according to how
they reflect evolutionary relationships
Fig. 26.10
I.
Phylogeny and Systematics
C.
Traits in Classification
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Establishing relationships among taxa
requires careful examination of characters
Ancestral characters = plesiomorphies
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Shared ancestral characters (symplesiomorphies)
unite descendants of a single ancestor into a
monophyletic clade
Ex: Vertebral column in vertebrates
Derived characters = apomorphies
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Shared derived characters = (synapomorphies) unite
derived clades and separate them from ancestral
clades
Ex: Amniote egg and feathers in reptiles/birds and
birds
Fig. 26.11
II.
Ecology
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“Ecology” from Greek “Oikos” (house)
Interactions among groups of organisms
and between organisms and physical
environment
Includes abiotic and biotic components
Fig. 52.17
• Physiological
• Behavioral
• Evolutionary
Fig. 52.2