Transcript EVOLUTION
EVOLUTION the CHANGE in populations over time. CHARLES DARWIN – English biologist who proposed the theory of evolution – Wrote The Origin of Species in 1859 (20 years after voyage); very controversial Darwin on HMS Beagle (a 5 year voyage) Darwin explains natural selection: 1. VARIATION exists among members of a population Recall lab: the species of finch that varied in their beak shape! Fish, for example, may differ in color, size, and speed. What causes variation? • Mutations (initially) • Sexual reproduction makes different combinations of traits possible Adaptations: • A variation that helps an organism to survive 2. Those with adaptations survive and reproduce AND pass on the adaptation to the offspring • Ex. Speedy fish survive Recall lab: the spoon and fork varieties were more successful than the knife ones At getting pasta food. The survive and offspring inherit this successful variation. 3. Over time, successful variations make up most/all of the population •The population may look quite different from their ancestors Recall lab: After five generations, the knife variation was almost nonexistant, Whereas the fork and spoon numbers climbed. Evidence For Evolution: 1. Direct Evidence for evolution: (we can see it happening in a short period of time). In bacteria, antibiotic resistance How it happens: (p. 399) Non-resistant bacterium Antibiotic Resistant bacterium The bacteria in a population vary in their ability to resist antibiotics. When the population is exposed to an antibiotic, only the resistant bacteria survive.— natural selection! The resistant bacteria live and produce more resistant bacteria. • Today, penicillin no longer kills as many species of bacteria because some species have “evolved” into penicillin-resistant populations. 2. Indirect Evidence for Evolution: (we can’t see it happening in a short period of time) a. Fossils • they provide a record of early life and how it is different from species today • The fossil record is incomplete (most things decompose rapidly and do not fossilize)!) Camel Evolution Age Organism Skull and teeth Limb bones Paleocene 65 million years ago Eocene 54 million years ago Oligocene 33 million years ago Miocene 23 million years ago Present b. Anatomy • Structural features with a common evolutionary origin are called homologous structures. • Homologous structures can be similar in arrangement, in function, or in both. Crocodile forelimb Whale forelimb Bird wing Anatomy (cont.) •Analagous structures: no common ancestor, but have common function • For example, insect and bird wings probably evolved separately when their different ancestors adapted independently to similar ways of life. Anatomy (cont.) • Many organisms have vestigial structuresstructures that no longer have a function. • they show structural change over time. • Vestigial structures, such as pelvic bones in the baleen whale, c. Embryology • the shared features in the young embryos that suggest evolution from a distant, common ancestor. Pharyngeal pouches Fish Reptile Pharyngeal pouches Bird Mammal • The embryos of a fish, a reptile, a bird, and a mammal have a tail and pharyngeal pouches. d. Biochemistry If the makeup of certain molecules is more similar, that would suggest a closer evolutionary relationship. Percent Substitutions of Amino Acids in Cytochrome c Residues Comparison of Organisms Biochemical Similarities of Organisms Two orders of mammals 5 and 10 Birds vs. mammals 8-12 Amphibians vs. birds Fish vs. land vertebrates 14-18 18-22 Insects vs. vertebrates 27-34 Algae vs. animals 57 Convergent Evolution = different species evolve in similar ways Divergent Evolution: same ancestral species evolve different adaptations over time due to different environments Some Structural Adaptations: Mimicry: One species resembles another species The viceroy (Limenitis sp.; right) and monarch (Danaus sp.) butterflies look very similar but may differ in their taste to avian predators. Camouflage= kind of mimicry in which a species blends in with its surroundings • NPR Too Big to Publish http://www.npr.org/templates/story/story.php?storyId=100542500&ps=rs NPR interview • http://www.youtube.com/watch?v=XV8h6J H8zVw&safety_mode=true&persist_safety _mode=1&safe=active • http://www.youtube.com/watch?v=PvAi8m 7EUgc&safety_mode=true&persist_safety _mode=1&safe=active Darwin’s finches • http://www.youtube.com/watch?v=l25MBq 8T77w&safety_mode=true&persist_safety _mode=1&safe=active