Name _______________________ Period ___________
Chapter 22: Descent with Modification: A Darwinian View of Life
As you study this chapter, read several paragraphs at a time to catch the flow of ideas and understand the reasoning that is being described. In some places, the text describes a narrative or story of events that led to Darwin’s theory of evolution. Therefore, first read the narrative to absorb the big picture and then return to answer the few questions that accompany this material. AP Biology Big Idea 1 is evolution, the primary topic of Chapters 22–26, but as you have seen, evolution is woven throughout the entire book.
Overview
1. Define evolution broadly and then give a narrower definition, as discussed in the overview.
2. Evolution can be viewed as a pattern and as a process. The pattern is a fact; how is the pattern revealed?
3. What is the process of evolution?
Concept 22.1 The Darwinian revolution challenged the traditional view of a young Earth inhabited by unchanging species
This section takes a look at the historical setting and influences on Darwin, and it sets the stage for our formal study of evolution.
4. How did each of the following sources view the origin of species?
Aristotle and Scala Naturae:
The Old Testament:
5. Explain the role of fossils in rock strata as a window to life in earlier times.
6. How would Georges Cuvier have explained the appearance of the record of life shown in the rock strata?
7. James Hutton and Charles Lyell were geologists whose ideas strongly influenced Darwin’s thinking. What were the ideas each of them contributed?
James Hutton:
Charles Lyell:
8. What is the importance of the principle of uniformitarianism?
9. Jean-Baptiste de Lamarck proposed a mechanism for how life changes over time. Explain the two principles of his mechanism.
use and disuse:
inheritance of acquired characteristics:
Concept 22.2 Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life
11. Charles Darwin proposed that the mechanism of evolution is natural selection and that it explains how adaptations arise. What are adaptations? Give two examples of adaptations.
12. Explain the process of natural selection.
13. Let’s try to summarize Darwin’s observations that drive changes in species over time:
Observation Cite an Example
1. Variations in traits exist.
2. These variations (traits) are heritable.
3. Species overproduce.
4. There is competition for resources; not all offspring survive.
14. From these four observations, what two inferences did Darwin make?
Inference #1.
Inference #2.
16. To demonstrate your understanding of this section, complete the following sentences:
_____________ do not evolve. _______________ evolve.
Now, take out your highlighter and mark the information in the box above. Hold these ideas firmly in your brain! Finally, if you are ever asked to explain Darwin’s theory of evolution by natural selection (a common AP essay question), do not pull out the phrase “survival of the fittest.” Instead, cite the points made in question 13 and explain the inferences that are drawn from them.
Concept 22.3 Evolution is supported by an overwhelming amount of scientific evidence
17. Use Inquiry Figure 22.13 in your text to explain how research with soapberry bugs demonstrated observable evolutionary change. Describe what each graph shows, and the method used to determine mean beak length prior to introduction of a new food source. What evidence was given to indicate that natural selection can occur very rapidly?
18. Antibiotic resistance has become a serious medical concern, and is an example of evolution in bacteria. Your text explores this problem with a look at MRSA, in the news today because it is becoming
increasingly more common. What is MRSA?
19. How did MRSA become so dangerous? Explain the evolution of MRSA’s resistance to methicillin.
21. The primary headings of this concept list four areas of important evidence for evolution. List these, then give an example that supports each type of evidence.
Evidence for Evolution Example
22. How does the fossil record give evidence for evolution?
23. What is meant by each of the following terms?Give an explanation and example of each.
Term Explanation/Example
Homologous structures
Vestigial structures
Analogous structures (see p. 475)
24. Figure 22.17 in your text shows an evolutionary tree. What is indicated by each branch point in the following figure? Mark each branch point. What is indicated by the hatch marks?
25. What number represents the common ancestor of mammals and birds? Why are mammals more closely related to birds than to amphibians?
27. To develop an evolutionary tree, what are the two distinct types of evidences that are used?
28. Organisms that are only distantly related can resemble each other. Explain convergent evolution, and describe how analogous structures can arise.
29. Convergent evolution might be summarized like this: Similar problem, similar solution. Can you give two examples of convergent evolution?
30. What is biogeography? How is the concept of biogeography supported by continental drift and the presence of endemic species?
Study Tip
Homologous structures show evidence of relatedness (whale fin, bat wing).
Let’s wrap up all of these ideas with a final summary.
Test Your Understanding Answers
Now you should be ready to test your knowledge. Place your answers here:
1. 2. 3. 4. 5.
ORGANIZE YOUR THOUGHTS
1. Evolution is change in species over time. 2. Heritable variations exist within a population.
3. These variations can result in differential reproductive success.
4. Over generations, this can result in changes in the genetic composition of the population.
Name _______________________ Period ___________
Chapter 23: The Evolution of Populations
This chapter begins with the idea that we focused on as we closed the last chapter: Individuals do not evolve! Populations evolve. The Overview looks at the work of Peter and Rosemary Grant with Galápagos finches to illustrate this point, and the rest of the chapter examines the change in populations over time. As in the last chapter, first read each concept to get the big picture and then go back to work on the details presented by our questions. Don’t lose sight of the conceptual understanding by getting lost in the details! EU 1.A,
“Change in the genetic makeup of a population over time is evolution,” is thoroughly covered in this chapter. You also need to be able to use the Hardy-Weinberg equation to make predictions about evolving
populations, so do the practice problems
Overview
1. What is microevolution?
2. What are the three main mechanisms that can cause changes in allele frequency?
3. What is the only mechanism that is adaptive, or improves the match between organisms and their environment?
Concept 23.1 Genetic variation makes evolution possible
4. Differences among individuals show two common patterns. One type of variation is between “either-or” characters, and the other is when the character varies along a continuum. Explain the underlying genetic differences that contribute to each pattern.
c. Explain how a substitution error in an exon could have no effect on the amino acid sequence.
6. Several sources of genetic variation are available. What is the ultimate source of new alleles
7. 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? Do point mutations always result in a change of phenotype?
8. What is neutral variation? Give an example from Figure 23.4.
9. Chromosomal changes that delete, disrupt, or rearrange many loci at once are usually harmful. How does gene duplication occur? How mightit play a role in evolution?
10. Much of the genetic variation that makes evolution possible comes through sexual reproduction. What are the three mechanisms by which sexual reproduction shuffles existing alleles?
1. 2. 3.
Concept 23.2 The Hardy-Weinberg equation can be used to test whether a population is evolving
11. What is a population?.
13. The greater the number of fixed alleles, the lower the species’ diversity. What does it mean to say that an allele is fixed?
14. The Hardy-Weinberg principle is used to describe a population that is not evolving. What does this principle state?
15. If the frequency of alleles in a population remains constant, the population is at Hardy-Weinberg equilibrium. There are five conditions for Hardy-Weinberg equilibrium. It is very important for you to know these conditions, so enter the conditions of the left side of the chart and a brief explanation of the condition on the right side.
CONDITIONS FOR HARDY-WEINBERG EQUILIBRIUM
Conditions For Hardy-Weinberg Equilibrium
It is not very likely that all five of these conditions will occur, is it? Allelic frequencies change. Populations evolve. This data can be tested by applying the Hardy-Weinberg equation.
16. In a plant population, suppose 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? (A complete solution for this problem is at the end of this Reading Guide chapter.)
17. 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. A complete solution for this problem is at the end of this Reading Guide chapter.)
Equation for Hardy-Weinberg Equilibrium
p2 + 2pq + q2 = 1
Where p2 is equal to the frequency of the homozygous dominant in the population, 2pq is equal to the frequency of all the heterozygotes in the population, and q2 is equal to the frequency of the homozygous recessive in the population.
Consider a gene locus that exists in two allelic forms, A and a, in a population.
Let p = the frequency of A, the dominant allele
and q = the frequency of a, the recessive allele.
So,
p2 = AA, q2 = aa, 2pq = Aa
If we know the frequency of one of the alleles, we can calculate the frequency of the other allele: p + q = 1, so
Concept 23.3 Natural selection, genetic drift, and gene flow can alter allele frequencies in a population
18. First, let’s try to summarize the big idea from this section. Scan through the entire concept to pull out this information. Three major factors alter allelic frequency and bring about evolutionary change. List each factor, and give an explanation.
Factor Explanation
19. Which of the factors results in a random, nonadaptive change in allelic frequencies?
20. Which of the factors above tends to reduce the genetic differences between populations and make populations more similar?
21. Of the three factors you previously listed, only one results in individuals that are better suited to their environment. Which is it?
22. Explain what happens in each of these examples of genetic drift:
founder effect:
bottleneck effect:
24. What is the relative fitness of a sterile mule?
25. Figure 23.13 is important because it helps explain the three modes of selection. Label each type of selection, and fill in the chart to explain what is occurring.
26. What is often the result of sexual selection?
27. What is the difference between intrasexual selection and intersexual selection? Give an example of each type of selection.
28. Explain two ways in which genetic variation is preserved in a population.
29. Natural selection can act to maintain genetic variability due to balancing selection. Explain and give an example of the two mechanisms of balancing selection:
a. Heterozygote advantage (Read Figure 23.17, Make Connections, to develop your response.) Type of Selection How It Works
Stabilizing Directional
b. Frequency-dependent selection
30. Give four reasons why natural selection cannot produce perfect organisms.
1. 2. 3. 4.
Test Your Understanding Answers
Now you should be ready to test your knowledge. Place your answers here:
Solution to Question 17
Let p = frequency of the dominant allele (R) and q = frequency of the recessive allele (r).
1. q2 = frequency of the homozygous recessive = 25% = 0.25. Because q2 = 0.25, q = 0.5.
2. Now, p + q =1, so p = 0.5.
3. Homozygous dominant individuals are RR or p2 = 0.25, and they will represent (0.25)(500) = 125 individuals.
4. The heterozygous individuals are calculated from 2pq = (2)(0.5)(0.5) = 0.5, and in a population of 500 individuals will be (0.5)(500) = 250 individuals.
Solution to Question 18
This problem requires you to recognize that individuals with the dominant trait can be either homozygous or heterozygous. Therefore, you cannot simply take the square root of 0.64 to get p. For problems of this type, you must begin with the homozygous recessive group. So . . .
Let p = frequency of the dominant allele (R) and q = frequency of the recessive allele (r)
1. q2 = frequency of the homozygous recessive = 36% = 0.36. Because q2 = 0.36, q = 0.6.
2. Now, p + q =1, so p = 0.4.
Name _______________________ Period ___________
Chapter 24: The Origin of Species
The processes by which one species splits into two are described in this chapter. New species arise when two populations diverge from a common ancestor sufficiently to become reproductively isolated. The rate of speciation may vary, and evidence that it has occurred includes the fossil record and genomic data. This chapter will provide background knowledge for EKs 1.C.1, 1.C.2, and 1.C.3.
Overview
1. What was Darwin’s “mystery of mysteries”?
2. Define speciation..
3. Distinguish between microevolution and macroevolution.
Concept 24.1 The biological species concept emphasizes reproductive isolation
4. Use the biological species concept to define species.
8. The following charts summarize the various ways that reproductive isolation is maintained. Explain and give an example of each type of isolating mechanism. Figure 24.3 will help with this task.
Prezygotic Reproductive Barriers
Explanation Example
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
Concept 24.2 Speciation can take place with or without geographic separation
10. What type of speciation is caused by a barrier such as the Grand Canyon?
11. Sympatric speciation occurs in populations that live in the same geographic area. How is this possible?
12. Your response to question 11 should have listed polyploidy, habitat differentiation, and sexual selection. These are not easy concepts to understand, so let’s spend some time with each of them. To begin, use the following figure to explain autopolyploidy.
13. Now, use this figure to explain allopolyploid speciation
Concept 24.4 Speciation can occur rapidly or slowly, and it can result from changes in few or many genes
16. Stephen Jay Gould and Niles Eldredge coined the term punctuated equilibria. What is meant by a punctuated pattern?
17. Label this figure, and explain how each of the pictures explains speciation.
Test Your Understanding Answers
Now you should be ready to test your knowledge. Place your answers here:
