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The Galapagos mockingbirds differ only slightly in size, shape, and coloration.

The Galapagos mockingbirds differ only slightly in size, shape, and coloration. Nesomimus melanotis. Nesomimus macdonaldi. Nesomimus parvulus. Nesomimus trifasciatus. Darwin reasoned that they are similar because they share a common ancestor. N. melanotis. N. macdonaldi. N. trifasciatus.

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The Galapagos mockingbirds differ only slightly in size, shape, and coloration.

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  1. The Galapagos mockingbirds differ only slightly in size, shape, and coloration. Nesomimus melanotis Nesomimus macdonaldi Nesomimus parvulus Nesomimus trifasciatus Darwin reasoned that they are similar because they share a common ancestor. N. melanotis N. macdonaldi N. trifasciatus N. parvulus

  2. Evidence for Evolution • Evidence that Species are Related • Geographic proximity of similar but distinct species. • Homologies: structural, developmental, and genetic.

  3. Structural homology Humerus Radius and ulna Carpals Metacarpals Phalanges Bird Bat Turtle Human Horse Seal

  4. Developmental homology Both the chick and the human have gill pouches and tails Gill pouch Tail Chick Human

  5. Present-day sloth Fossil sloth

  6. Evidence for Evolution • Evidence that Species Change over Time: • Law of succession • Evidence of extinctions in the fossil record • Vestigial traits

  7. Human coccyx Capuchin monkey tail (used for balance, locomotion)

  8. Erect hair on chimp (insulation, emotional display) Human goosebumps

  9. Box 21.2 Figure 1a Analogy: When similarities result from convergent evolution 1m 1m Ichthyosaur Common dolphin Whales and dolphins Monotremes Ichthyosaurs Pterosaurs Elephants Marsupials Synapsids Dinosaurs Primates Rodents Lizards Birds The members of lineages between the dolphins and ichthyosaurs do not have adaptions like: - streamlined bodies - long jaws filled with teeth - fins and flippers The dolphin and ichthyosaur lineages are far apart on the evolutionary tree, suggesting that they are not closely related

  10. Box 21.2 Figure 1b Homology: When similarities are inherited from a common ancestor Fruit fly HOM complex Human Hox complex abdAabdB lab pb Dfd Antp b-1 b-2 b-3 b-4 b-5 b-6 b-7 b-8 b-9 Ubx Molluscs (snails, clams, squid) Echinoderms (sea stars, sand dollars) Chordates (vertebrates) Arthropods (insects, spiders, crustaceans) Annelids (segmented worms) Flatworms As shown in the two boxes above, the loci found in the Hox and HOM complexes of fruit flies and humans have similar sequences and are in the same order on their chromosomes

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