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Intro to Natural Selection Sept 2008 “Survival of the fittest” Get set: What have you learned? • Survival depends on: – Being able to obtain adequate amount of food and water. – Being able to protect one’s self from predation. – Having characteristics to deal with the environment (climate, soil, plants, other animals.) – Being able to reproduce to keep the species alive. What happened to the animals in round 1 of the Staying Alive simulation? • Toothpickta could not obtain enough food when • climate changes affected their natural food source. Toothpickta became extinct. What happened to the animals in round 2 of the Staying Alive simulation? • Tweezarian had slight variations in their pinchers. • Variations (mutations) are random – some are helpful, some are not. • Those with the helpful variation thrive and the tweezarian population eventually all display the “improved” variation. What happened to the animals in round 3 of the Staying Alive simulation? • Non-native species can be invasive. • Native plant/animals can be affected when non-native species are introduced. • Over-feeding can cause a disaster for the entire ecosystem. A scientific Explanation • A theory is based on a number of observations or experiments. • A theory attempts to explain natural phenomenon. Natural Selection • the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less welladapted individuals do. Variations happen by chance Some variations are helpful; some harmful What does the theory say ? helpful variations = survival Those who survive, pass traits to young Charles Darwin • An English naturalist • studied animals on Galapagos Island • Wrote the famous book: On the Origin of Species by Means of Natural Selection. • Had a major impact on scientific community. SPECIATION • THE FORMATION OF NEW SPECIES • AS NEW SPECIES DEVELOP, POPULATIONS BECOME REPRODUCTIVELY ISOLATED • REPRODUCTIVE ISOLATION – MEMBERS OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE OFFSPRING. Table 23.1a These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation. Table 23.1b Fig. 23.6 Four species of leopard frogs: differ in their mating calls. Hybrids are inevitable. Hawaiian Honeycreepers An example of adaptive radiation – these species all diverged from a common ancestor (founder species) FOUNDER SPECIES SPECIATION IN DARWIN’S FINCHES • SPECIAITON IN THE GALAPAGOS FINCHES OCCURRED BY: - FOUNDING OF A NEW POPULATION, - GEOGRAPHIC ISOLATION which led to - REPRODUCTIVE ISOLATION and CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION. Can species combines in new and different ways today? http://www.nps.gov/archive/chis/r m/IslandFox/index.htm Tigon Result of male tiger and female lion mating in captivity. Offspring are infertile. Separated both geographically and ecologically. Liger Result of male lion and female tiger mating in captivity. Offspring are infertile. Closure: Summarize What you’ve learned: • Name 4 parts of Natural Selection. • Explain how speciation can occur.