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Honors Biology: Chapter 15 Review 1. If evolution is the change in allelic frequencies of a population over time, what causes it to happen? (There are five things!) natural selection, mutation, gene flow, genetic drift (as a result of a small population) and nonrandom mating 2. What are two causes of genetic drift? Population bottleneck and founder effect 3. Draw a picture showing a population before and after recovering from a bottleneck. Your picture should clearly show how this affects genetic diversity. Initial Population Bottleneck Population After Recovery ABCDEF GHIJKLM ABEFAB ABEF ABEFEF 4. Draw a picture showing the founder effect. Show the parent population the founders and the founding population many generations later. Be sure to how this affects genetic diversity. Parent Population ABCDEF GHIJKLM Founders AB B Founding Population Later ABABAB ABABAB 5. Why is genetic diversity important in populations? Increase the chance that some individuals will have the variations necessary to survive as environmental conditions change. Increase fitness of population. Decrease risk of extinction. Lower chance of having to inbreed and the negative effects associated with it. 6. What type of selection is occurring in each of the following examples: a. Large lizards are easily seen and captured by birds. Small lizards cannot escape predation by snakes. Stabilizing b. Male/Male competition and female choice direct this form of selection. Sexual c. Ducks with short bills are able to obtain food floating on the pond surface. Ducks with long bills can obtain food on the bottom of the pond. Disruptive d. Only the thickest bills are able to crack the nuts, the only available food source. Directional e. The most colorful male fish have the most success attracting a mate. Sexual 7. True or False. If the statement is false explain why. Most natural populations are in equilibrium. False; most are evolving Mutations arise in response to changes in the environment. False, mutations arise by random chance Genetic drift has a larger impact on small populations.True Natural selection acts on individual genotypes. False, individual phenotypes Populations evolve, not individuals. True Competition between members of the same species results in coevolution. False coevolution occurs between different species (different species evolve in response to one another) Components of the abiotic environment that act as agents of natural selection are predation and competition. False these are components of the biotic environment Low genetic diversity in elephant seals and cheetahs are the result of the founder effect. False, population bottleneck Sum total of all the alleles in a Term that describes when a population population is not evolving Gene Pool Genetic equilibrium Form of selection that acts on traits that allow an individual to acquire a mate. Sexual Changes in allelic frequencies due to random chance events Changes in the DNA that result in new variations in a population mutation The movement of genes between populations Genetic drift Gene flow Form of selection that favors the average for of a trait and selects against the extreme forms. Stabilizing Traits or characteristics that help an individual survive and reproduce. Adaptation A group of individuals belonging to the same species living in the same geographic area. population When two species evolve in response to one another coevolution Form of selection that favors one extreme form of a trait and selects against the average and other extreme. When two or more phenotypes are maintained in a population due to selective advantage of the directional When both extreme forms of a trait are favored and the average is selected against. disruptive Measured by the number of offspring an individual leaves behind fitness heterozygote. Balanced polymorphism Individuals with favorable variations have the greatest reproductive success Natural selection