Download Chapter 22: Descent wffh Modification: A Darwinian View of Life

Chapter 22: Descent with Modification: A Darwinian View of Lift
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Period
Chapter 22: Descent wffh Modification: A Darwinian View of Life
As you study this chapteL read several paragraphs at a time to catch the flow of ideas and understan(i
the reasoning that is being described. In some places, the text describes a narrative or story regardinÿ
the events that led to Darwin's theory of evolution. Therefore, first read the narrative to absorb thÿÿ
big picture and then return to answer the few questions that accompany this material.
1. Define evolution broadly and then give a narrower definition, as discussed in the overview.
This section takes a look at the historical setting and influences on Darwin, and it sets the stage fo,:
our formal study of evolution.
.
How did each of the following sources view the origin of species?
Aristotle and Scala Naturae
The Old Testament
CaroMs Linnaeus
3. Explain the role of fossils in rock strata as a window to life in earlier times.
4. How would Georges Cuvier have explained the appearance of the record of life shown in th
rock strata?
.
James Hutton and Charles Lyell were geologists whose ideas strongly influenced Darwin ÿ
thinking. What were the ideas each of them contributed?
James Hutton
Charles Lyell
6. What is the importance of the principle of uniformitarianism?
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Chapter 22: Descent with Modification: A Darwinian View of Life
7. 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
8. Although Lamarck's mechanism of evolution does not explain the changes in species over time,
his thinking has been influential. What is considered to be the great importance of his ideas?
9. 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 them.
10. Explain the process of natural selection.
11. Let's try to summarize Darwin's observations that drive changes in species over time:
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1. Variations in traits exist.
2. These variations (traits) are heritable.
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3. Species overproduce.
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4. There is competition for resources; not all
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offspring survive.
12. From these four observations, what two inferences did Darwin make?
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It is important to remember that differences in heritable traits can lead to differential reproductive success. This means that the individuals who have the necessary traits to promote survival
in the current environment will leave the most offspring. How can this differential reproductive
success affect the match between organisms and their environment?
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14. To demonstrate your understanding of this section, complete the following sentences:
do not evolve,
evolve.
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Chapter 22: Descent with Modification: A Darwinian View of Life
Now, take out your highlighter and mark the information in the previous box. 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 11 and explain the inferences that are drawn from them.
15. Use Figure 22.13 in your text to explain how research with soapberry bugs demonstrated observable evolutionary change.
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16. MRSA is in the news today because it is becoming increasingly more common. What is it?
17. How did it become so dangerous? Explain the evolution of MRSA's resistance to methicillin.
18. Do antibiotics cause bacteria to become resistant? Explain your response.
19.
Let's make a list of the four evidences for evolution that are described in this concept. Give an
example of each.
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Chapter 22: Descent with Modification: A Darwinian View of Life
20. How does the fossil record give evidence for evolution?
21. What is meant by each of the following terms? Give an example of each.
22. How do homologous structures give evidence for evolution?
23. What is summarized in an evolutionary tree?
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.
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25. What is indicated by the hatch marks in Figure 22.17?
26.
Use the tree in question 24 to answer this question: Are crocodiles more closely related to lizards or to birds? Explain your response.
27.
On the evolutionary tree, label the vertical lines to the right, and annotate the key feature that
marks each group.
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28. Organisms that are only distantly related can resemble each other. Explain convergent evolution, and describe how analogous structures can arise.
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Chapter 22: Descent with Modification: A Darwinian View of Life
Convergent evolution might be summarized like this: Similar problem, similar solution. Can you
29.
give two examples of convergent evolution?
Study Tip
Homologous smÿctures show evidence of relatedness (whale fin, bat wing).
Analogous structures are similar solutions to similar problems but do not indicate close relatedness
(bird wing, butterfly wing).
30. What is biogeography? How is it affected by continental drift and the presence of endemic
species?
Let's wrap up all of these ideas with a final summary.
OR GANIZE I70 UR THO UGHTS
1.
2.
3.
4.
Evolution is a change in a species over time.
Heritable variations exist within a population.
These variations can result in differential reproductive success.
Over generations, this can result in changes in the genetic composition of the
population.
And remember: Individuals do not evolve! Populations evolve.
Test Your Understanding Answers
Now you should be ready to test your knowledge. Place your answers here:
1.
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2.
3.
4.
5.
Chapter 23: The Evolution of Populations
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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
Galitpagos 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!
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?
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4. Because Darwin did not know about the work of Gregor Mendel, he could not explain how
organisms pass heritable traits to their offspring. In looking at genetic variation, what are
discrete characters, and what are quantitative characters?
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5. Using the techniques of molecular biology, what are the two ways of measuring genetic varia-
tion in a population?
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Geographic variation may be shown in a graded manner along a geographic axis known as a
cline. What external factors might produce a dine? Why does the existence of a cline suggest
natural selection?
7. Several sources of genetic variation are available. What is the ultimate source of new alleles?
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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? Why don't all point mutations result in a change of phenotype?
9. What is translocation? How can it be beneficial?
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Chapter 23: The Evolution of Populations
10. Chromosomal changes that delete, disrupt, or rearrange many loci at once are usually harmful.
How does gene duplication occur? How might it play a role in evolution?
11. 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?
12. What is apopulation?
13. What is a gene pool?
14. The greater the number of fixed alleles, the lower the species' diversity. What does it mean to
say that an allele isfixed?.
15. The Hardy- Weinberg principle is used to describe a population that is not evolving. What does
this principle state?
16.
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 on the left side of the chart
and a brief explanation of the condition on the right side.
CONDITIONS FOR HARDY-WE][NBERG EQUILIBRI[UM
.
2.
3.
4.
5.
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. Let's
look at how to do this.
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Chapter 23: The Evolution of Populations
Eqÿaÿ.cÿ ÿbr Har@o;Wehÿerg Eqaÿbrÿm
p2 + 2pq + q2 = I
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
p=l-q
q=l-p
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17.
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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.)
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18.
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.)
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Chapter 23: The Evolution of Populations
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 evolu-
19.
tionary change. List each factor, and give an explanation.
20. Which of the previous factors results in a random, nonadaptive change in allelic frequencies?
21. Which of the previous factors tends to reduce the genetic differences between populations and
make populations more similar?
22. Of the three factors you previously listed, only one results in individuals that are better suited
to their environment. Which is it?
23. Explain what happens in each of these examples of genetic drift:
founder effect
bottleneck effect
24.
In evolutionary terms, fitness refers only to the ability to leave offspring and contribute to
the gene pool of the next generation. It may have nothing to do with being big, or strong, or
aggressive. Define relative fitness.
25. What is the relative fitness of a sterile mule?
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Chapter 23: The Evolution of Populations
26. Figure 23.13 in your text 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.
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Stabilizing
Directional
Disruptive
27. What is often the result of sexual selection?
28.
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What is the difference between intrasexual selection and intersexual selection? Give an example
of each type of selection.
29. Explain two ways in which genetic variation is preserved in a population.
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30. Discuss what is meant by heterozygote advantage, using sickle-cell anemia as an example°
31. Give four reasons why natural selection cannot produce perfect organisms.
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Chapter 23' The Evolution of Populations
Test Your Understanding Answers
Now you should be ready to test your knowledge. Place your answers here:
1.
2.
3.
4.
5.
6.
Solution to Questioÿ 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. Since q2 = 0.25, q = 0.5.
2. Now, p+q= 1, sop=0.5.
3ÿ 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) = 251} individuals.
Solution to Questiot7 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.
2ÿ
3.
Now, p + q = 1, sop = 0.4.
Notice that this problem asks for the frequency of the dominant allele (p), not the
frequency of the homozygous dominant individuals (p2). So, you are done.., the
frequency of the dominant allele = 40%.
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Chapter 24: The Origin of Species
Name
Period
Chapter 24: The Origin of Species
1. What was Darwin's "mystery of mysteries"?
2. Define speciation.
3. Distinguish between microevolution and macroevolution.
Concept 24d 7Yÿe biological :ÿyecfes c(mceS eÿgdmsi:ÿ:es rÿrodg, cff,,e fsod;ÿ¢foJÿ
4. Use the biological species concept to define species.
5. What is required for the formation of new species?
6. What are hybrids?
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7. Explain the two types of barriers that maintain reproductive isolation.
,
The following charts summarize the various ways that reproductive isolation is maintained.
Explain and give an example of each type of isolating mechanism.
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Habitat isolation
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Temporal isolation
Behavioral isolation
Mechanical isolation
Gametic isolation
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Chapter 24: The Origin of Species
Reduced hybrid viability
Reduced hybrid fertility
Hybrid breakdown
,
The concept of reproductive isolation is essential for an understanding of speciation, so we are
going to have you look at it again. Refer to Figure 24.3 in your text, and label the following
sketch. Name each type of isolating mechanism.
.... .......... ...................... ................................. " ........ ,, ................ .............. '" ................. 'ÿ;' ..................... ;b
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Chapter 24: The Origin of Species
Colÿeept 24.2 HOeciaAoÿ cÿm ÿke p&ce ÿ,h"}ÿ or n,iA}oÿd geogrÿgBMc s<bÿr'aAoÿ'
10. Gene flow can be interrupted in two main ways. Explain and give an example of each by labeling and
annotating this figure, which shows an ancestral species of fish and then the two modes of speciation.
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11. What type of speciation is caused by a barrier such as the Grand Canyon?
12. Sympatric speciation occurs in populations that live in the same geographic area. How is this possible?
13.
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Your response to question 12 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.
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Chapter 24: The Origin of Species
14. Now, use this figure to explain allopolyploid speciation.
15. Before we leave allopatric and sympatric speciation, explain what happens in sexual selection,
and how this process can drive sympatric speciation.
Calmep¢ 24,3 f<ÿ;bAd ;;oÿes' proÿ,Me <ÿBortÿmities go ,ÿ'mdy f(ÿe¢ors t}}at eau,ve rÿ<gÿrod?ÿcth,e isolÿHoÿ
] 6. What are hybrid zones?
Cotmept 24.4 5)ÿedatioÿ eÿ'm oeem° rÿ¢Ndÿ), or sloÿ@ÿ, cmd # ealÿ res'ÿ# Ji'om ehÿt<ÿ<es #ÿ.ibÿ, or mayO, geÿes'
17. Stephen Jay Gould and Niles Eldredge coined the term punctuated equilibria. What is meant by
a punctuated pattern?
18. 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:
1.
2.
6,
7.
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3.
4.
5.