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