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Transcript
Evolution Ch 15 G1-2 I. Darwin A. General Facts 1. 1831 – 22 yr. old Charles Darwin set sail on 5 yr. voyage on HMS Beagle 2. Job – a. record plants and animals b. mapping of S. America and S. Pacific 3. Observations a. Marine fossils 14,000 ft above sea level b. land lifted by earthquakes c. living sloths and bones of much larger sloths d. 13 similar, but separate species of Galapagos Island finch (distinctive bills for particular food sources). e. Many of Galapagos Island’s organisms similar to mainland with slight differences. 4. Galapagos Island Species 1. Cormorants – fly on mainland/ flightless on island. 2. Iguana – leaf eating on mainland with sm. Claws/ sea weed eating with lg. claws on island. 5. Publication of “Origin of Species” a. worked with Alfred Wallace (species collector) b. Hypothesis – natural selection c. Presented hypothesis in 1858 B. Darwin’s Theories 1. Descent with Modification a. newer forms in fossil record are modified descendants of older species. b. All species descended from one or a few original types of life. 2. Modification by Natural Selection a. Adaptive Advantage – favorable traits – allow greater adaptation/ greater likelihood of surviving descendants – pass on traits. b. Unfavorable traits – less likelihood of offspring – traits are not passed on c. Selection conditions change as the environment changes d. Rapid changes in environment lead to extinction. B. Evidence of Evolution 1. Homologous and Analogous Structures a. Homologous features – similar features that originated in common ancestor (finches’ beak) b. Examples – homologous features: penguins, alligator, bats and humans all have very different arms – all share a humerus, radius, ulna, carpals, metacarpals, and phalanges. c. Analogous Structures – Serve identical functions, but have very different anatomy and embryologic development *Theory – traits evolved independently – not related (example: humming birds and bees both hover over flowers). 2. Vestigial Structures – a. Serve no useful function (example: humans have a tailbone and appendix/ some snakes have tiny pelvic bones and limb bones/ whales have pelvic bones and 4-chambered stomaches/ sm. Percentage of sperm whale have tiny leg bones.) 3. Embryology – a. Many different vertebrates look very similar in early fetal development (fish, rabbit and gorilla) p291 4. Similarities in Macromolecules – a. Amino acid sequences of homologous proteins (example: hemoglobin are similar among different species). b. The more closely related, the more similar the amino acid sequence (human and gorilla hemoglobin differ by one amino acid/ human and frog hemoglobin differ by 67 amino acids). II Patterns of Evolution A. Coevolution 1. Predators and their prey often coevolve 2. Plant-eating animals and plants often coevolve (example: bats feed on nectar, flowers are light in color to see at night) B. Convergent Evolution – 2 unrelated organisms evolve similar traits 1. Some organisms look similar, but are not related (shark and porpoise). 2. Occurs when environment selects similar phenotypes (streamlined bodies and similar fins). C. Divergent Evolution – 2 related organisms become more dissimilar 1. Changes in environment lead to different adaptations. 2. Adaptive Radiation – many species evolve from single ancestral species (different food sources, climate, etc.). 3. Artificial selection – selective breeding in domestic plants and animals (much quicker than natural selection).