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EVOLUTION

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Students know and understand the characteristics and structure of living things, the processes of life, and how living things interact with each other and their environment. Benchmark 3.18: Organisms change over time in terms of biological evolution and genetics.

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Darwin, the Beagle and Finches: 3:59 Darwins Discoveries: 10:10 Gene frequency, natural selection, speciation: 29:00 What do you get when you cross a mouse with a mango? 4:15 Why did the woolly mammoth become extinct? 2:17 Total time: 49:41 min. (approximately)

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The modern theory of evolution began when Charles Darwin presented evidence that evolution happens and offered an explanation of how evolution happens. Darwin, the Beagle and Finches (3:59)

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In natural selection, individuals that have traits that better suit their environment are more likely to survive. Artificial selection occurs when humans breed offspring to promote desirable traits like different breeds of dogs. QuickLab pg. 378. Darwins discoveries (10:00)

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In Darwins time, the science of geology was born. By studying fossils in rock formations such as the Burgess shale formation in Yoho Park, Canada, scientists eventually deduced that species evolve gradually over long periods of time. Gene frequency, natural selection, speciation (29:00)

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1. Overproduction: Every population is capable of producing more offspring than can possibly survive. 2. Variation exists within every population. Much of this variation is in the form of inherited traits. 3. Selection: In a given environment, having a particular trait can make individuals more or less likely to survive and have successful offspring. So, some individuals leave more offspring than others do. 4. Adaptation: Over time, those traits that improve survival and reproduction will become more common.

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The link between microevolution and macroevolution is speciation. Speciation is the formation of a new species as a process of genetic change or as a pattern of change in the form of organisms. QuickLab pg. 387 What do you get when you cross a mouse with a mango? (4:15)

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Natural selection Causes an increase or decrease in certain alleles in a population. Migration The movement of individuals into, out or between populations. Changes the types of alleles in a population. Mate Choice Random pairing of mates increases the assortment of traits. Mutation Changes the numbers and types of alleles from generation to generation. Genetic Drift Random effects of everyday life can affect the survival and reproduction in populations, thus some alleles can become more or less prevalent.

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Convergent evolution is strongly directed by environment species living in the same type of environment should evolve similar adaptations.

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Coevolution: Species that live close together can affect one anothers evolution. Species that live in close contact often have clear adaptations to one anothers existence. Coevolution between the yucca moth and the yucca plant. A female yucca moth (Tegeticula yuccasella) pushing pollen into the stigma tube of the yucca flower while visiting the flower to deposit her eggs.

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Over time, species may split into two or more lines of descendants or lineages. As the splitting repeats, one species can give rise to many new species. Darwins finches Adaptive Radiation (13:04)

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If all members of a lineage die off or fail to reproduce, the species is said to be extinct. Evolution and Sexual Reproduction Evolution and Sexual Reproduction Why did the Wooly Mammoth become extinct? (2:17)

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Gradualism is a model used to describe the formation of a new species through small, gradual changes as opposed to large-scale changes. Punctuated equilibrium is where new species suddenly appear in response to environmental changes. Chapter 16 Lab pg. 391