BIOL108 Lecture Notes - Lecture 3: Convergent Evolution, Symplesiomorphy, Monophyly
21 Jun 2018
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Lecture 3
Systematics Cont.:
oSynapomorphy: is a shared, derived state (useful for reconstructing phylogenetic
relationships)
oSymplesiomorphy: shared, ancestral state (nothing new)
oHomologous character states: look the same and have the same evolutionary origin
oAnalogous character states: appear the same but actually evolved independently
(convergent evolution)
Ex: wings or fins – similar functions but different inheritance / ancestors
Convergent evolution: independent evolution of similar traits in different
lineages
oMonophyletic: contains a common ancestor and ALL of its descendants AND NO OTHER
unrelated taxa (mono = one)
A monophyletic group = clade
oPolyphyletic group: taxa get clumped together even though they do not share recent
ancestors
More than one common ancestor
OR lacking common ancestry that unites members in the group
OR incorrectly grouped by superficial similarities – not due to common ancestry
Bats and birds being in the same group (DO NOT share a recent
common ancestor)
oWings on bats and wings on birds are analogous
oParaphyletic Group:
Groups that do not contain ALL descendants of a common ancestory
Often result of the excluding taxa that are highly divergent from the rest of their
clade
find more resources at oneclass.com
find more resources at oneclass.com
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BIOL108 Full Course Notes
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Document Summary
Ex: wings or fins similar functions but different inheritance / ancestors. Convergent evolution: independent evolution of similar traits in different lineages: monophyletic: contains a common ancestor and all of its descendants and no other unrelated taxa (mono = one) A monophyletic group = clade: polyphyletic group: taxa get clumped together even though they do not share recent ancestors. Or lacking common ancestry that unites members in the group. Or incorrectly grouped by superficial similarities not due to common ancestry. Bats and birds being in the same group (do not share a recent common ancestor: wings on bats and wings on birds are analogous, paraphyletic group: Groups that do not contain all descendants of a common ancestory. Often result of the excluding taxa that are highly divergent from the rest of their clade. Evolution accounts for the unity and diversity of life. All life on earth is related because it evolved from a common ancestor.
