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Published byMorris Crawford Modified over 9 years ago
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Evolution How Gene Pool Change Occurs
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What exactly is a SPECIES? Species: Group of similar organisms that can breed and produce fertile offspring Example: Labrador and Pitt Bull Non-example: Horse and Donkey
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The formation of a new species from a preexisting population is called: SPECIATION.
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Changes in the gene pool can cause the population to evolve Changes in the gene pool may be a result of many different causes Causes of Change
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Standard 8d Students know reproductive or geographic isolation affects speciation.
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Causes of Change 1.Mutations in the genes (DNA) of individuals causing new adaptations. Are mutations always bad? 2.Reproductive Isolation: individuals unable to breed together: behavior or physical characteristics
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Types of Reproductive Isolation 1.Geographic Isolation- population is split by some physical barrier: river, mountain, ocean i.e. Albert & Kaibab squirrels of the Grand Canyon 2.Behavioral Isolation- two populations are capable of interbreeding but have different mating rituals or routines. i.e. eastern & western meadowlarks
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3. Temporal Isolation- two or more species reproduce at different times. i.e. three types of rain forest orchids
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Standard 8c Students know the effects of genetic drift on the diversity of organisms in a population.
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Sometimes the gene pool just changes…… Genetic Drift is cause of evolution by random chance No Natural Selection Happens in small populations
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2 types of Genetic Drift 1. Bottleneck Effect- a high percentage of a population is killed by a random act reducing variation in the gene pool. 2. Founder Effect- change in allele frequencies as a result of the migration of a small subgroup of a population
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