Name______________________________ Class __________________ Date ______________

Chapter 16 Evolution of Populations

Section 17–1 Genes and Variation (pages 482–486)

Genetics Joins Evolutionary Theory

1. Natural selection works on an organism’s                              rather than its                     .

2. A(n)                           consists of all the genes, including the alleles for each gene, that are present in a population.

3. A gene pool typically contains different                             for each heritable trait.

4. The number of times that an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur is called the                                                           of the population.


5.      In the diagram below, use circles to represent the alleles within each segment of the population. Draw the B alleles as solid circles and the b alleles as outline circles. The total number of individuals in this population is                                                                                    ; the total number of alleles is      .
















6. How many alleles for black fur are in the sample population and what percentage of allele frequency does that represent?


7. How many alleles for brown fur are in the sample population and what percentage of allele frequency does that represent?


8. Describe how a geneticist might be able to tell that this population is evolving.


Sources of Genetic Variation


9.      What are mutations? When do they affect evolution?



10.  Identify two ways in which genes can be recombined during meiosis.



11.  What is lateral gene transfer? How does it affect variation?




Single-Gene and Polygenic Traits


12.  Label the two graphs to show which one represents a single-gene trait and which one

represents a polygenic trait.


                          13. The number of phenotypes produced for a given trait depends on how many genes control the trait.

                           14. Height in humans is an example of a single-gene trait.


                          15. Each gene of a polygenic trait often has two or more phenotypes.

                          16. A single polygenic trait often has many possible genotypes.

                          17. A symmetrical bell-shaped graph is typical of polygenic traits.


18.  Why is genetic variation important to the process of evolution?


Section 17–2 Evolution as Genetic Change in Populations (pages 487–493)

How Natural Selection Works

19.  If a trait made an organism less likely to survive and reproduce, what would happen to the allele for that trait?



20.  If a trait had no effect on an organism’s fitness, what would likely happen to the allele for that trait?


21.   List the three ways that natural selection can affect the distributions of phenotypes.







22.  What effect does stabilizing selection have on variation in a population?



Match the type of selection with the situation in which it occurs.

Type of Selection                               Situation


_____23. Directional                           a. Individuals at the upper and lower ends of the curve

have higher fitness than individuals near the middle.


_____24. Stabilizing                            b. Individuals at one end of the curve have higher fitness

than individuals in the middle or at the other end.


_____25. Disruptive                            c. Individuals near the center of the curve have higher

fitness than individuals at either end.


26.  Draw the missing graph to show how disruptive selection affects beak size.

Genetic Drift

27.    In small populations, random changes in       ___________________ is called genetic drift.


28.     A situation in which allele frequencies change as a result of the migration of a small subgroup of a population is known as the __________________________________.


29.     The ___________________________________________ is a change in allele frequency following a dramatic reduction in the size of a population.



30.    Complete the concept map.
















Evolution Versus Genetic Equilibrium

31.    What does the Hardy-Weinberg principle state?



32.     What is genetic equilibrium?



33.     List the five conditions that can disturb genetic equilibrium and cause evolution to occur.

a.                                                                     d.


b.                                                                     e.




34.  Explain how sexual selection results in non-random mating.

Genetic drift has less effect on large populations.

No movement into or out of the population

Very large

Section 17–3 The Process of Speciation (pages 494–497)

new species

Isolating Mechanisms

35.  What is speciation?



36.  What does it mean for two species to be reproductively isolated from each other?



37.  What must happen in order for new species to evolve?


38.   List three ways that reproductive isolation occurs.







39.  When does behavioral isolation occur?



40.  When does geographic isolation occur?



41.  What is an example of temporal isolation?



Speciation in Darwin’s Finches


42.  Peter and Rosemary Grant spent years on the Galápagos Islands studying changes in __________________________________ populations.

43.  Many finch characteristics appear in bell-shaped distributions typical of     _________ traits.

44.   The ancestors of the Galápagos Island finches originally came from the continent of          __________________________.

45.   The populations of finches on separate islands are _______________________________ isolated from one another by large stretches of open water.

46.  Big-beaked finches that prefer to mate with other big-beaked finches are    ____________  isolated from small-beaked finches living on the same island.



Section 17–4 Molecular Evolution (pages 498–501)


Timing Lineage Splits: Molecular Clocks


47.  What is a molecular clock?


48.  Why are only neutral mutations useful for molecular clocks?


49.  Why are there many molecular clocks in a genome instead of just one?






Use the diagram of an ancestral species to answer Questions 50-51. Each picture in the diagram represents a gene. Each shaded portion of a gene represents a mutation.

50.   Which species is most closely related to Species B? Explain your answer.







51.   How can you tell that Species C is probably not a descendant of the organism with Gene 2?









Gene Duplication

                52.  Multiple copies of a duplicated gene can turn into a group of related genes called

A. globins.

B. duplicates.

C. a Hox gene.

D. a gene family.

                53.  A chromosome may get several copies of the same gene during the process of

A. crossing-over.

B. gene mutation.

C. gene expression.

D. artificial selection


Developmental Genes and Body Plans


54.  What genetic factors might be responsible for a change in an organism’s body plan?