chapter 3 opener diverse adaptations to a dry environment patterns of evolution
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Chapter 3 Opener Diverse adaptations to a dry environment
Patterns of Evolution
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Figure 3.1 Tracing the path of evolution to Homo sapiens from the universal ancestor of all life
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Figure 3.2 Monophyletic, paraphyletic, and polyphyletic groups
Goal: classification should reflect evolutionary historyCladistic approaches best
Sister groups
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Figure 3.3 Two possible histories of change of a character in the Hominoidea
Inferring the history of character evolution: Occam’s razor
What are the monophyletic groups
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Figure 3.4 A phylogeny of strains of human immunodeficiency virus and simian immunodeficiency viruses
Cladistic analysiscan have practicalapplications; e.g.,inferring the originof a pathogen
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• General Evolutionary Pattern 1
• Most of the attributes of organisms have evolved by modification of preexisting attributes.
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Figure 3.5 The forelimb skeletons of some tetrapod vertebrates
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• General Evolutionary Pattern 2
• Homoplasy is common.
• Convergent evolution– Resemblance between distantly related
organisms.
• Parallel evolution– Resemblance between closely related
organisms.
• Character state reversals– e.g., from derived to ancestral condition
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Figure 3.6 The eyes of (A) a vertebrate and (B) a cephalopod mollusc are an extraordinary example of convergent evolution
Convergent evolution
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Path of light Path of nerve impulsetransmission
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Figure 3.8 Convergent evolution based on mutations of the same gene, Mc1r
Perognathus intermedius Aspidoscelis inornata
Mc1r product: a signal protein for melanin production
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Figure 3.7 Parallel evolution
Modified developmental pathway: accessory mouthparts from legs
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Figure 3.9 Phylogeny, based on DNA sequences, of part of the salamander family Plethodontidae
Character reversal
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Figure 3.10 Four bird groups in which similar bill shape has evolved independently as an adaptation for feeding on nectar
Differentfamilies