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Published byCaroline Barber Modified over 9 years ago
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TYPES OF NATURAL SELECTION
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Directional Selection Stabilizing Selection Disruptive Selection DEFINE IN YOUR NOTES
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A form of natural selection; occurs when individuals at one end of the distribution curve have higher fitness than individuals in the middle or at the other end of the curve. One EXTREME is favored. DIRECTIONAL SELECTION
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Example: Giraffes Selection for a long neck DIRECTIONAL SELECTION
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A form of natural selection; occurs when individuals near the center of a distribution curve have higher fitness than individuals at either end. EXTREMES are NOT selected AVERAGE is better. STABILIZING SELECTION
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Example: Human infant birth weight—it is a disadvantage to be really small or really big, and it is best to be somewhere in between. STABILIZING SELECTION
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A form of natural selection; occurs when two individuals at the upper and lower ends of a distribution curve have higher fitness than individuals near the middle. BOTH EXTREMES are selected for. DISRUPTIVE SELECTION
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DARWINS FINCHES DISRUPTIVE SELECTION
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WORD ASSOCIATIONS Directional = 1 extreme Stabilizing = Average Disruptive = 2 extremes
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Structure's that evolve because of the same environmental pressures. For example, Birds and Bats. They do not have a recent common ancestor, but have managed to both evolve wings. ANALOGOUS STRUCTURES
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THE FOUNDER EFFECT The loss of genetic variation when a new colony is formed by a very small number of individuals. (This is why incest is not good) http://www.dnalc.org/view/15184-Mitochondrial-DNA-and-the-founder-effect-Douglas- Wallace.html
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ISOLATING MECHANISMS When a new species evolves it’s because a population has become reproductively separated.
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REPRODUCTIVE ISOLATION THERE’S 3 TYPES When members of 2 populations cannot interbreed and make fertile offspring. This is why we will never have a real life CatDog. Different species CANNOT combine and reproduce.
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BEHAVIORAL ISOLATION This is when the same species are CAPABLE of reproducing but DON’T because they have different mating rituals. Like a lion and a cheetah. BOTH are felines (cats) BUT they DON’T mate with each other.
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GEOGRAPHIC ISOLATION When species are separated by a geographic barrier, like an ocean, river or mountains. Like a Brown Bear and a Polar Bear They are BOTH bears BUT they are geographically separated so they can’t mate.
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TEMPORAL ISOLATION When species reproduce at different times. For example, these 2 different types of frogs BOTH are frogs BUT one mates in the spring, while the other mates in the fall
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ISOLATING MECHANISMS Each of these could lead to the development of a new species. https://www.youtube.com/watch?v=2oKlKmrbLoU
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