Bio 2 Ch. 23 – Flashcards
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Understand what a phylogeny represents
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• Hypothesis about patterns of relationship among species
• Cladogram or phylogenetic tree
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What is systematics?
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Reconstruction and study of evolutionary relationships
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Explain why phenotypic similarity does not necessarily indicate close evolutionary relationship.
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• Rates of evolution vary
• Evolution is not always divergent
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Describe the difference between ancestral and derived similarities.
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• Derived characteristic: inherited from the most recent common ancestor of an entire group
• Ancestral characteristic: similarity that arose prior to the common ancestor of the group
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Explain why only shared, derived characters indicate close evolutionary relationship.
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Derived characters are determined from comparison to a group known to be closely related, termed an out group.
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Understand how a cladogram is constructed.
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Minimizes the amount of character evolution required
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Differentiate among monophyletic, paraphyletic, and polyphyletic groups.
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• Monophyletic (clade): includes the most recent common ancestor of the group and all its descendants.
• Paraphyletic: includes the most recent common ancestor of the group but not all its descendants.
• Polyphyletic: does not include the recent common ancestor of all members of the group.
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Explain the meaning of the phylogenetic species concept and why it is controversial.
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• Emphasizes the possession of shared derived characters
• Controversial: looks to the past to see if separated long enough to develop their own derived characters. And PSC can be applied to both sexual and asexual species
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Explain the importance of homoplasy for interpreting patterns of evolutionary change.
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Homologos traits are derived from the same ancestral character states, whereas homoplastic traits are not, even though they may have similar function.
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Describe how phylogenetic trees can reveal the existence of homoplasy.
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They examine the distribution of traits amoung species in a context of their phylogenetic relationships.
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Discuss how a phylogenetic tree can indicate the timing of species diversification.
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By correlating phylogenetic branching with known evolutionary events.
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Discuss how phylogenetic analysis can help identify patterns of disease transmission.
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Track the evolution of disease strains, uncovering sources and progression. Ex. HIV
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Convergent evolution
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Similar characters not derived from common ancestery.
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Synapomorphy
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Derived character shared by clade members
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Homoplasy
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A shared character state that has not been inherited from a common ancestor.
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Principle of parsimony
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The cladogram that requires the fewest number of evolutionary changes is favored.
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Classification
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How we place species and higher groups into the taxonomic hierarchy - should follow evolutionary history.
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Biological species concept (BSC)
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Focuses on reproductive isolation.
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Homologous structures
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Derived from the same ancestral source.
Ex. Dolphin flipper and horse leg
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Analogous
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Similar function due to similar selection pressures.
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Homoplastic convergence
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Evolving separately due to adaptations to the enviroment.
Ex. Plant conducting tubes
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Plesiomorphies
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Ancestral state.
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Symplesiomorphies
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Shared ancestral state.
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All organisms share many characteristics:
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Composed of one or more cells
Carry out metabolism
Transfer energy with ATP
Encode hereditary information in DNA
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Darwin envisioned that all species were descended from a single common ancestor.
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"Descent with modification"
We are constantly changing.
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Characters should exist in recognizable character states
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Presence vs. absence
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__________ may not accurately predict evolutionary relationships
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Similarity
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Looking at a cladogram what part is a derived feature?
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Is only shared by part of the cladogram.
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Looking at a cladogram what part is a ancestral feature?
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Is shared by the whole group.
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Outgroup comparison
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• Species or group of species that is closely related to, but not a member of.
• Out group may or may not exhibit ancestral form
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Simian immunodeficiency virus (SIV)
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• Found in 36 species of primates
• Does not usually cause illness
