Natural Selection “Survival of the Fittest ” PASTPRESENT.

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Natural Selection Survival of the Fittest PASTPRESENT Slide 2 Phenotype vs. Genotype Natural selection acts on ________ rather than _________. Those best suited for their environment will ________ (taller giraffes). Those least suited for their environment ___ faster and leave ________ offspring (short giraffes). PASTPRESENT phenotype genotype survive die fewer Tt tt tt tt Tt tt tt TT Slide 3 Genetic variation is essential! ________ promote genetic variation, which helps ensure a species survival. Therefore, mutations are NATURAL and INCREASE genetic diversity Reproduction(Crossing over) promotes genetic variation which helps to ensure a species survival Mutations Slide 4 Adaptation Some phenotypic feature or trait that improves an organisms likelihood of survival and reproduction How might this adaptation have occurred and how is it beneficial? What would you expect to happen to the deer population in the next 1000 years? In Georgia, there is a popular hunting area of forest, where the hearing-deer live. This species of deer has 6 ears. Slide 5 Differential survival of groups of organisms (who is going to live?) 1.Those groups of organisms who are best adapted (fittest) to their environment will survive, while the least adapted will eventually die out (differential survival). 2. Those that survive get to reproduce 3.The trait MUST be genetic to be passed on to next generation. Slide 6 Changing Environments When the environment changes, those who are now fittest will survive and repopulate. Why is it important for a species to have variation? Slide 7 Which rabbit will survive better here? Slide 8 What about here? Slide 9 Charles Darwin 1 st credited with theory of Evolution Wrote the Origin of Species Book based on his observations during trip to Galapagos. Made detailed sketches and notes to record observations. Slide 10 Prezygotic and Postzygotic barriers Geographic isolation organisms, originally of same species (in same area) got physically separated and were no longer able to mate Reproductive Isolation organisms become genetically incompatible or offspring are not viable or offspring are not fertile. Slide 11 Squirrel A and B live on opposite sides of the Grand Canyon. Even though they are different species, dont they look similar? Geographic Isolation Slide 12 Reproductive Isolation X mule Slide 13 Speciation =process of new species formation, typically due to a favoring of certain traits. Slide 14 Speciation

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