Mutation and sexual reproduction produce the genetic variation that makes evolution possible. [2]

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1 GUIDED READING - Ch. 23 POPULATION EVOLUTION NAME: Please print out these pages and HANDWRITE the answers directly on the printouts. Typed work or answers on separate sheets of paper will not be accepted. Importantly, guided readings are NOT GROUP PROJECTS!!! You, and you alone, are to answer the questions as you read. You are not to share them with another students or work together on filling it out. Please report any dishonest behavior to your instructor to be dealt with accordingly. Get in the habit of writing legibly, neatly, and in a NORMAL, MEDIUM-SIZED FONT. AP essay readers and I will skip grading anything that cannot be easily and quickly read so start perfect your handwriting. Please SCAN documents properly and upload them to Archie. Avoid taking photographs of or uploading dark, washed out, side ways, or upside down homework. Please use the scanner in the school s media lab if one is not at your disposal and keep completed guides organized in your binder to use as study and review tools. READ FOR UNDERSTANDING and not merely to complete an assignment. Though all the answers are in your textbook, you should try to put answers in your own words, maintaining accuracy and the proper use of terminology, rather than blindly copying the textbook whenever possible. Remember: INDIVIDUALS DO NOT EVOLVE! POPULATIONS EVOLVE. As in the last chapter, first read each concept to get the big picture, then go back to work on the details in these questions. Don t lose sight of the conceptual understanding by getting lost in the details! Define the term microevolution. a. What are the three main mechanisms that can cause changes in allele frequency? [2] 3. b. Which is the only mechanism that is adaptive, meaning they improved the match between organisms and their environment? [2] Mutation and sexual reproduction produce the genetic variation that makes evolution possible. [2] 3. Because Darwin did not know about the work of Gregor Mendel, he could not explain how organisms pass heritable traits to their offspring. a. In looking at genetic variation, what are Discrete Characters? [2] b. How are these discrete characters often genetically determined? Why?

2 c. What are Quantitative Characters? [2] d. How are these discrete characters often genetically determined? Why? 4. a. Using the techniques of molecular biology, what are the two ways of measuring genetic variation in a population? b. What does it mean if a certain population has an average heterozygosity of 20% but a nucleotide variability of 5%/ 5. What do we mean by when we say that two separate populations may show geographic variation? 6. a. Geographic variation may be shown in a graded manner along a geographic axis known as a. [2] b. Geographic variation may or may not be caused by natural selection. Explain. c. Why does the existence of a cline, however, suggest natural selection? [2] 7. a. What is the ultimate source of new alleles?

3 b. When do these mutations become a part of the next generation s gene pool, part of the genotypes of the offspring? Why? 8. Let s see if you understand. Why is genetic variation within a population a prerequisite for evolution? [1] 9. a. Mutations are any change in the nucleotide sequence of an organism s DNA. These mutations provide the raw material from which new traits may arise and be selected. What occurs in a point mutation? b. Why do most point mutations have no or a negative effect on organisms? c. When is a point mutation beneficial and does it spread among a population s members? 10. a. What is a translocation mutation? b. Though usually harmful, how could it be beneficial? [2]

4 1 a. What three events could lead to gene duplication? 3. b. Importantly, how might gene duplication play a role in evolution?! {2] 1 Much of the genetic variation that makes evolution possible comes through sexual reproduction. Explain the three mechanisms by which sexual reproduction shuffles existing alleles? If a sexually reproducing population suddenly started reproducing asexually only, how would its genetic variation be affected over time? Explain. [1] The Hardy-Weinberg equation can be used to test whether a population is evolving [2] 14. To review, define the term population? 15. What is a population s gene pool? 16. a. The greater the number of fixed alleles, the lower the species diversity. When do we say that an allele is fixed within a population s gene pool?

5 b. Suppose a population of organisms with 500 loci is fixed at half of these loci and has two alleles at each of the other loci. How many different alleles are found in its entire gene pool? Explain. [1] 17. The Hardy-Weinberg Principle is used to desire a population that is NOT evolving! What does the Hardy- Weinberg Principle state? 18. In reference to the frequencies of the alleles and genotypes in a population, what does it mean when a population is in Hardy-Weinberg equilibrium? 19. What are the five conditions for Hardy-Weinberg Equilibrium. Explain each one. (It is very important for you to know and understand these five!)

6 20. It is very unlikely that all five of these conditions will occur and that the allelic or genotypic frequencies will stay the same for every single gene loci in a population, though one loci may be in Hardy-Weinberg Equilibrium while other are evolving. Allelic frequencies do often change. Populations do evolve. The data can be tested by applying the Hardy-Weinberg Equation. Lets look at how to do this next. [2] a. Lets try a problem. Show your work in full below. Suppose in a plant population that red flowers (R) are dominant to white flowers (r). In a population of 500 individuals, 25% show the recessive phenotype. How many individuals would you expect to be homozygous dominant and heterozygous for this trait? [2] b. Show your work in full below. In a population of plants, 64% exhibit the dominant flower color (red), and 36% of the plants have white flowers. What is the frequency of the dominant allele? (There are a couple of twists in this problem, so read and think carefully.) [2] c. Show your work in full below. For a locus with two alleles (A and a) in a population at risk from an infectious neurodegenerative disease, 16 people had a genotpye AA, 92 had a genotype Aa, and 12 had a genotype aa. Is this population evolving or not? [1]

7 Natural Selection, genetic drift, and gene flow can alter allele frequencies in a population. [2] 2 First, let s try to summarize the big idea from this section. Read over the section and pull out this information. Three major factors (in addition to mutations and sexual selection) alter allelic frequency and bring about evolutionary change. List each factor, and give an explanation. [2] FACTOR #1 = Explanation FACTOR #2 = Explanation FACTOR #3 = Explanation 2 Which of the factors above results in a random, nonadaptive change in allelic frequencies? Why? [2]

8 23. Which of the factors above tends to reduce the genetic differences between populations and make populations more similar? Why? [2] 24. Of the three factors you listed, only one results in individuals that are better suited to their environment. (INDIVIDUALS WITH ADAPTATIONS). Which is it and why? 25. Explain what happens in each of these examples of genetic drift [2] and why it is considered evolution. a. Founder Effect b. Bottleneck Effect

9 26. In what sense is natural selection more predictable than genetic drift? [1] 27. Explain the four effects of Genetic Drift as summarized in your text Suppose two plant populations exchange pollen and seeds. In one population, individuals of genotype AA are most common (9000AA, 900Aa, 100aa), while the opposite is true in the other population (100AA, 900Aa, and 9000aa). If neither allele has a selective advantage, what will happen over time to the allele and genotype frequencies of these populations? [1]

10 Natural selection is the only mechanism that consistently causes adaptive evolution. [2] 29. In evolutionary terms, being fit may have nothing to do with being big, or strong, or aggressive. [2] What is the difference between the terms fitness and relative fitness. [3] 30. What is the relative fitness of a sterile mule? [2] 3 Why is it said that natural selection acts on phenotypes and not genotypes? [3] 3 The diagram below shows the three different modes of selection that may affect the hypothetical mouse population with heritable variation in fur color. The graph shown the change in fur color frequencies, the white arrows symbolizing selective pressure against the ancestral populations phenotype. Name each mode of selection and explain how each type works in the space below.

11 33. Consider a population in which heterozygotes at a certain locus have an extreme phenotype, such as being larger than homozygotes, that also confers a selective advantage. Does such a situation represent directional, disruptive, or stabilizing selection? Explain. [1] 34. a. What is sexual selection? b. What is often the result of sexual selection [2], what is it, and why does it result? 35. a. What is the difference between intrasexual selection and intersexual selection? [2] b. Give an example of each type of selection. [2] 36. One hypothesis about how female preference for certain male characteristics evolves, is that females who have a tendency to like males whose appearance is correlated with good genes have healthier offspring and pass those genes for the preference of these types of males to their offspring as well in higher numbers. Review Figure Why did the researchers split each female frog s eggs into two batches for fertilization by different males? Why did they not just mate different females with each of the different males?

12 37. Explain four ways in which genetic variation is preserved in a population despite natural selection s tendency to reduce unfavorable genotypes and despite directional or stabilizing selection Sickle-cell anemia is a largely lethal disease caused in individuals who inherit the homozygous recessive genotype. How is the sickle-cell anemia allele s presence in the sub-saharan desserts population related to heterozyge advantage?

13 39. Finally, give four reasons why natural selection cannot produce perfect organisms. [2] Please check your answers to question 20 to make sure you understood. 20.a. 20.b.

14 Solution to Question 20.c. There are 120 in the population, so there are 240 alleles. There are 124 A 4 Please answer the Self-Quiz at the end of your chapter. Do your best to try it from memory first in order to test how well you grasped the material References Campbell et al. (2008). AP* Edition Biology. 8th Ed. San Francisco: Pearson Benjamin Cummings. Adapted from Fred and Theresa Holtzclaw 3. Adapted from L. Miriello