1. Module 8

1.10. Page 3

Lesson 2

Module 8—Populations, Individuals and Gene Pools

 

Reflect and Connect

 

This lesson has examined some historical examples of gene pool change. Are there current examples? 


The human immunodeficiency virus (HIV) causes acquired immune deficiency syndrome (AIDS), which is fatal without treatment.  However, not all people infected with HIV go on to develop AIDS. Scientists have discovered that the gene that codes for a cell receptor for HIV has a recessive allele that makes the receptor non-functional. This means that people who are homozygous for this recessive allele will not develop AIDS even though they are infected with HIV. Population geneticists are wondering what will happen to the frequency of this recessive allele in the future. The Lesson 2 Assignment will investigate this question.

 

Before you begin the Module 8: Lesson 2 assignment, you may wish to answer the “Review” questions on page 697.

 

Module 8: Lesson 2 Assignment

 

Retrieve the copy of the Module 8: Lesson 2 Assignment that you saved to your computer earlier in this lesson. Complete the assignment. Save your completed assignment in your course folder. You will receive instructions later in this lesson on when to submit your assignment to your teacher.

 

This is a photo of a pair of grey wolves.

© Ryan Jaime/10082931/ Fotolia.com

Discuss

 

When populations become small, much of the variation in the gene pool is lost, which makes them more susceptible to extinction if the environment changes. The grey wolf suffered such a fate and nearly disappeared from Montana’s Glacier National Park.

 

With the guidance of your teacher, and working with fellow students in groups, prepare discussion material for a debate regarding the advantages and disadvantages of introducing the grey wolf back into Montana’s Glacier National Park. Half of the class should take the role of local community members and ranchers; the other half should take the role of wildlife managers and proponents of wildlife. Prepare your positions by listing each of the arguments you will make. For each argument, list what you expect your opponent to counter with. Have a rebuttal ready for each of the anticipated opposing arguments. Your teacher may choose to carry out the debate in class or by using the discussion board tool. You may choose to do a web search to research the topic or use other sources. More information on the grey wolf plight is found in “Figure 19.10” on page 691 of your textbook.

 

Self-Check

 

SC 2. Which gene pool would most likely demonstrate microevolution?

  1. a breeding population of 3000 white swans on Slave Lake

  2. a forest population of red deer after the 1986 Chernobyl nuclear accident in Ukraine

  3. a population of mule deer that includes some that have recently joined the population after fleeing from widespread forest fires in central BC

  4. a small population of Acacia trees isolated on an island by rising ocean levels

SC 3. Which correctly matches a term to its description?

  1. gene flow: a chance change in allele frequencies when small populations become isolated

  2. natural selection: a particular phenotype of mate is more often chosen, changing the frequency of the alleles in the gene pool

  3. change in mutation rate: several new alleles arise by mutation or a change in the rate of mutation from B to b and b to B

  4. genetic drift: chance changes in allele frequencies that occur in small populations
Check your work.
Self-Check Answers

 

SC 2.

  1. This does not demonstrate microevolution because the population is quite large and chance changes due to small populations (genetic drift) are unlikely to be a factor. This population will tend to favour equilibrium.

  2. This population would likely show microevolution, but not necessarily. Nuclear contamination will certainly increase mutation rates, but if mutation from one allele to the other is equal, then allele frequencies may not change substantially. If mutation occurs more in one direction, microevolution will occur.

  3. Deer entering the population are immigrants and are participating in gene flow. If the immigrants are coincidentally different in phenotype/genotype than the original population, then allele frequencies will change, and microevolution will occur.

  4. The isolation of this tiny breeding population will likely cause a change in allele frequencies if the isolated population happens to be coincidentally slightly different in allele frequency than the original population. Also, if the rising water levels make a different set of environmental conditions on the island, then those individuals naturally selected on this island may be different from those that are naturally selected in the mainland population.

SC 3. Answers c and d are correct.

Answer a describes genetic drift, not gene flow.  

Answer b describes non-random mating or mate-selection, not natural selection.

 

Module 8: Lesson 2 Assignment

 

Submit your completed Module 8: Lesson 2 Assignment to your teacher for assessment.