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CHAPTER 15 Tracing Evolutionary History
Modules 15.6 – 15.14
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15.6 Key adaptations may enable species to proliferate after mass extinctions
Adaptations that have evolved in one environmental context may be able to perform new functions when conditions change Example: Plant species with catch basins, an adaptation to dry environments Figure 15.6
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15.7 “Evo-devo:” Genes that control development play a major role in evolution
“Evo-devo” is a field that combines evolutionary and developmental biology Major adaptations may arise rapidly if mutations occur in genes that control an organism’s early development
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Paedomorphosis, the retention of juvenile characteristics in the adult, seems to have played a role in human evolution Chimpanzee fetus Chimpanzee adult Figure 15.7A, B Human fetus Human adult
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Stephen Jay Gould argued that there was a connection between our juvenile physical traits and our long period of dependency The youthful features of Mickey Mouse elicit affectionate, parental responses Figure 15.7C
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15.8 Evolutionary trends do not mean that evolution is directed toward a goal
Evolutionary trends may reflect unequal speciation or survival of species on a branching evolutionary tree
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Figure 15.8
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15.9 Phylogenetic trees strive to represent evolutionary history
Phylogeny is the evolutionary history of a group of organisms
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Common ancestor from South America mainland
Cactus ground finch Small tree finch Medium tree finch Woodpecker finch Medium ground finch Small ground finch Large cactus ground finch Vegetarian finch Large tree finch Mangrove finch Green warbler finch Gray warbler finch Large ground finch Sharp-beaked ground finch Seed eaters Cactus flower eaters Bud eaters Insect eaters Ground finches Tree finches Warbler finches Common ancestor from South America mainland Figure 15.9
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15.10 Systematists classify organisms by phylogeny
SYSTEMATICS AND PHYLOGENETIC BIOLOGY Systematists classify organisms by phylogeny Reconstructing phylogeny is part of systematics the study of biological diversity and classification Taxonomists assign a two-part name to each species The first name, the genus, covers a group of related species The second name refers to a species within a genus
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Genera are grouped into progressively larger categories
Table 15.10
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Taxonomists often debate the particular placement of organisms in categories as they strive to make their categories reflect evolutionary relationships
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Felis catus (domestic cat) Mephitis mephitis (striped skunk)
Lutra lutra (European otter) Canis familiaris (domestic dog) Canis lupus (wolf) SPECIES GENUS Felis Mephitis Lutra Canis FAMILY Felidae Mustelidae Canidae ORDER Carnivora Figure 15.10
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15.11 Homology indicates common ancestry, but analogy does not
Homologous structures are evidence that organisms have evolved from a common ancestor In contrast, analogous similarities are evidence that organisms from different evolutionary lineages have undergone convergent evolution Their resemblances have resulted from living in similar environments
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Example: California ocotillo and allauidia of Madagascar
Figure 15.11
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15.12 Molecular biology is a powerful tool in systematics
Systematists increasingly use molecular techniques to classify organisms develop phylogenetic hypotheses Human Chimpanzee Gorilla Orangutan Figure 15.12B
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Common ancestral carnivorans
A phylogenetic tree based on molecular data Polar bear Asiatic black bear American black bear Giant panda Brown bear Sun bear Sloth bear Spectacled bear Lesser panda Raccoon Pleistocene Pliocene Miocene Ursidae Procyonidae Oligocene Common ancestral carnivorans Figure 15.12A
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15.13 Systematists attempt to make classification consistent with phylogeny
Homologous features are used to compare organisms Cladistic analysis attempts to define monophyletic taxa
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3 2 1 TAXA Outgroup (Reptiles) Ingoup (Mammals) Eastern box turtle
Duck-billed platypus Red kangaroo North American beaver CHARACTERS Long gestation Gestation Hair, mammary glands Vertebral column Long gestation 3 Gestation 2 Hair, mammary glands 1 Vertebral column Figure 15.13A
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Cladistic analysis is often a search for the simplest hypotheses about phylogeny
Phylogenetic tree according to cladistic analysis Lizards Snakes Crocodiles Birds Phylogenetic tree according to classical systematics Lizards Snakes Crocodiles Birds Figure 15.13B, C
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15.14 Arranging life into kingdoms is a work in progress
THE DOMAINS OF LIFE Arranging life into kingdoms is a work in progress For several decades, systematists have classified life into five kingdoms MONERA PROTISTA PLANTAE FUNGI ANIMALIA Earliest organisms Figure 15.14A
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A third domain, the Eukarya, includes all kingdoms of eukaryotes
A newer system recognizes two basically distinctive groups of prokaryotes The domain Bacteria The domain Archaea A third domain, the Eukarya, includes all kingdoms of eukaryotes BACTERIA ARCHAEA EUKARYA Earliest organisms Figure 15.14B
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