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Monday, February 13 Bell Work: Using an example how does natural selection occur? (not the elephant or the jaguar) Other Evidence for Evolution 1 Fossils Provides evidence that evolution occurred, but the record is incomplete. Give clues to the organisms age, location, and environment at that time. Scientists can still understand overall picture of how most groups evolved. Tiktaalik roseae…the missing link • 4 to 9 feet long • gills and fins of a fish • But its fins included shoulders, elbows, and wrists, like the limbs of land animals. • a crocodilestyle skull and the neck and ribs of an early land animal. • The scientists say their "fish with elbows" represents a major link in the evolutionary chain leading from ancient fishes to amphibious land 2 • Debate over whether this creature was the first bird or a dinosaur with birdlike characteristics Geography Darwin noticed that animals and plants on the islands were similiar to those on the mainland. He hypothesized that some individuals from the mainland migrated to the islands. Different ecosystems on different islands favored different traits and since the islands are too far apart for mating, interaction didn't occur. Biogeography study of the distribution or organisms around the world. 3 Embryology All embryos look similar, no matter the species, which suggests a common ancestor. -Fish, reptile, mammals and birds have pharyngeal pouches and tails. -In fish, the pharyngeal pouches become gills in the other organisms they become parts of the ears, jaw and throat. Homologous structural features that are similar in structure, but appear to have different functions suggest common descent Example Bones of forelimbs of whales, crocs and birds all are similar in structure, but different in function. Vestigial A body structure present in organisms that no longer serves a purpose. important so show evolution has occurred. Example Pelvic bones in whales, wings on ostriches, appendix in humans. (once used to digest cellulose in plants, we don't each much cellulose now) 4 Analogous body parts that do not have a common structure, but similar functions. do not suggest a common ancestor Example Bird and butterfly wings Scientists use all possible evidence to interpret evolutionary relationships between species. However, it is all subject to a scientists interpretation. Cannot observe evolution occurring because of short life span. 5 6