Chapter 3 Opener Diverse adaptations to a dry environment Patterns of Evolution
Dec 19, 2015
Chapter 3 Opener Diverse adaptations to a dry environment
Patterns of Evolution
Figure 3.1 Tracing the path of evolution to Homo sapiens from the universal ancestor of all life
Figure 3.2 Monophyletic, paraphyletic, and polyphyletic groups
Goal: classification should reflect evolutionary historyCladistic approaches best
Sister groups
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
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
• General Evolutionary Pattern 1
• Most of the attributes of organisms have evolved by modification of preexisting attributes.
Figure 3.5 The forelimb skeletons of some tetrapod vertebrates
• 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
Figure 3.6 The eyes of (A) a vertebrate and (B) a cephalopod mollusc are an extraordinary example of convergent evolution
Convergent evolution
Path of light Path of nerve impulsetransmission
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
Figure 3.7 Parallel evolution
Modified developmental pathway: accessory mouthparts from legs
Figure 3.9 Phylogeny, based on DNA sequences, of part of the salamander family Plethodontidae
Character reversal
Figure 3.10 Four bird groups in which similar bill shape has evolved independently as an adaptation for feeding on nectar
Differentfamilies