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15-3 Evolution in Process Evidence of evolution: Living organisms display many clues to their evolutionary history 1.Homologous and analogous structures: -Homologous features: are similar features that originated in a shared common ancestor and derived from the same structures in the embryo. Ex. Beaks of finches are modifications of a feature found in an ancestor common to all birds Ex. Limbs of humans, bats, alligators and penguins are very similar in skeletal structures -Presence of homologous features indicates the sharing of a recent common ancestor -Analogous features: serve similar functions but differ in structure and derived from different structures in the embryo Ex. Humming bird and humming moth, both can hover to feed on flowers nectar using their wings that evolved independently in each animal. 2.Vestigial structures: Are useless features for modern organisms, but were useful for an ancestor Ex. Human tailbone Ex. Human appendix Ex. Sperm whales vestigial pelvic bones and leg bones An organism with a vestigial structure probably shares a common ancestor with another that has a functional version of the same feature. 3.Similarities in embryology: -The early stages of different vertebrate embryos are similar (but they fade as development proceeds) -Such similarities can be taken as an indication of sharing a common ancestor 4.Similarities in macromolecules: -The amino acid sequences in human hemoglobin and gorilla differ by one amino acid, while between humans and frogs differ by 67 amino acids The more similar homologous proteins are in different species, the more closely they are related. Patterns of evolution Coevolution: is the change of 2 species in close association with each other Ex. Some species of bats feed on flowers’ nectar Bats: have slender long tongue with a brush tip to feed and have fur on their faces and necks to pick up pollen Flowers: have a fruity nectar and bright at night to attract bats and to be easily located by them. Convergent evolution Divergent evolution Occurs when the environment selects similar When 2 species become more dissimilar phenotypes even when the ancestors are resulting in new species different from each other 1. Adaptive radiation: where many related species evolve from a single ancestor Ex. Sharks look similar to porpoises Ex. Galapagos islands finches (dolphins) while sharks are fishes and 2. Artificial selection: where the process of porpoises are mammals divergence is sped up artificially They have been selected by the Ex. Breeding dogs for certain phenotypic environment they share by their large characteristics resulting in different breeds streamlined bodies and fins with different traits.