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Transcript
Evolution Sec. 16.1 Darwin and Natural Selection • Evolution: Change in a population over time • Galapagos Islands: -located off the west coast of South America -Darwin studied species of animals and plants; and found that species varied between islands GALAPAGOS ISLANDS SPECIES VARIATION BETWEEN ISLANDS Mathus • Discovered that the human population growth outpaces the food supply Darwin discovered species compete for survival • Food • Space • Finding mates • Escaping predators • Shelter SURVIVAL OF THE FITTEST • ONLY THE BEST FIT FOR THE ENVIRONMENT SURVIVE TO REPRODUCE! DARWINS DISCOVERIES • EACH GENERATION OF NEW SPECIES SHOWS VARIATION IN TRAITS THROUGH: 1. ARTIFICIAL SELECTION 2. NATURAL SELECTION ARTIFICIAL SELECTION • BREEDING ORGANISMS WITH SPECIFIC TRAITS TO PRODUCE OFFSPRING WITH IDENTICAL TRAITS DOG BREEDING: EX. OF ARTIFICAIL SELECTION NATURAL SELECTION • PROCESS OF SELECTION WHICH OCCURS IN NATURE • ORGANISMS WITH CERTAIN VARIATIONS SURVIVE, REPRODUCE AND PASS VARIATIONS TO NEXT GENERATION • ORGANISMS WITHOUT THESE VARIATIONS ARE LESS LIEKLY TO SURVIVE AND REPRODUCE. NATURAL SELECTION Natural Selection: ADAPTATIONS • VARIATIONS THAT AID ORGANISMS IN SURVIVAL IN THEIR ENVIRONMENT • Ex: thorns on plants, distinct coloration of animals • Darwin believed adaptations occurred over many generations. Structural Adaptations • Changes in an organisms appearance or physical traits MIMICRY • Structural adaptation • that allows one species to resemble another Harmless species often adapt to look like harmful to protect themselves from predators CAMOUFLAGE • STRUCTURAL • ADAPTATION THAT ENABLES SPECIES TO BLEND WITH THEIR SURROUNDINGS Prevents species from being seem by predators. PHYSIOLOGICAL ADAPTATIONS • Changes in an organisms metabolic processes • Ex: penicillin-resistant bacteria; pesticide resistant insects and weeds INDIRECT EVIDENCE OF EVOLUTION • Fossils • Anatomy • Embryology • Biochemistry 1. Fossils • Provide record of early life • Ex: Camels 2. Anatomy • Homologous structures: structures with common evolutionary origin - can be similar in structure, function, or both - believed structures are evidence of evolution from an common ancestor Homologous Structures Ex: Forelimbs 2. Anatomy • Analogous Structures: features that do not have a common evolutionary origin but are similar in function. • Ex: Butterfly wing and Bird wing Analogous Structures 2. Anatomy • Vestigial Structures: structures that have no function now but did in an ancestor • A structure becomes vestigial when it is no longer needed. Vestigial Structure Appendix is no longer used in humans so it is considered a vestigial structure. (need when we ate more of a plant based diet) 3. Embryology • Easy to distinguish adult bird and mammal but difficult to distinguish embryos. • Embryo: earliest stage of growth and development of an organism • Suggest evolution of common ancestors Embryology 4. Biochemistry • Compares DNA and RNA of different species to determine evolutionary relationships MECHANISMS OF EVOLUTION SEC. 15.2 POPULATION GENETICS • GENE POOL: ALL THE ALLELES OF A POPULAITONS GENES • ALLELE FREQUENCY: PERCENTAGE OF A SPECIFIC ALLELE IN A POPULATION • GENETIC EQUILIBRIUM: WHEN THE ALLELE FREQUENCY REMAINS THE SAME OVER GENERATIONS CHANGES IN GENETIC EQUILIBRUIUM • GENETIC DRIFT • NATURAL SELECTION: – STABILIZING SELECTION – DIRECTIONAL SELECTION – DISRUTIVE SELECTION GENETIC DRIFT • ALTERATION OF ALLELIC FEQUENCIES BY CHANCE EVENTS; COMMONLY OCCURS IN SMALL POPULATIONS • Ex: Amish Settlement in PA – 1 in 14 (short arms, legs, extra fingers and toes) – 1 in 1000 in US population in general STABILIZING SELECTION • Favors average sized individuals Small cannot compete for food; large are seen by predators. SEE #1 DIRECTIONAL SELECTION • Favors extreme variation See #3 Elephants with longer trunks are able to reach food/water more easily. DISRUPTIVE SELECTION • Favors either extreme See #2 Marine Limpets with white, tan and dark brown shells. The white and brown are camouflaged as rocks while tan are easily seen. EVOLUTION OF SPECIES (SPECIATION) • SPECIES: Groups of organisms that look alike and can interbreed to produce fertile offspring • SPECIATION: The evolution of a new species – Occurs when members of a population can no longer interbreed and produce fertile offspring. Geographic Isolation • Physical barrier divides population REPRODUCTIVE ISOLAION • GENETIC MATERIAL BECOMES TO DIFFERENT TO MATE. • BEHAVIOR: MAY MATE AT DIFFERENT TIMES OF YEAR • POLYPLOIDY: INDIVIDUALS WITH AN EXTRA SET OF CHROMOSOMES CANNOT MATE SUCCESSFULLY REPRODUCTIVE ISOLATION GRADUALISM VS. PUNCTUATED EQQUILBRIUM Gradualism • Believes change will happen slowly over many generations Punctuated • Change is rapid and then long periods of equilibrium occur between PATTERNS OF EVOLUTION • Adaptive radiation – Ancestors evolve into an array of species to fit the environment • Divergent evolution – Species becomes increasingly distinct from original ancestor • Convergent evolution – Unrelated species that occupy similar environments in different parts of the world undergo similar natural selection ADAPTAVIE RADIATION DIVERGENT EVOLUTION CONVERGENT EVOLUTION