ZOOL 404, Evolutionary Biology, Assignments

Homework is not required for this course.  However, consistent, timely and scholarly completion of these assignments should not only increase your appreciation for course material (and possibly improve your exam performance) but will also be counted favorably towerd your final grade.

• Standing assignments

• Weekly assignments, due at the beginning of class (1:00p.m.) on the Monday following the given week.
  • There will be no formal chapter-by-chapter assignments for this unit (covering Ridley, Part 3).  But see "standing assignments", below.  You are also encouraged to test your own understanding by attempting Ridley's end-of-chapter Study and Review Questions and the tutorial questions on the Ridley CD.
  • Old assignments for prior test periods.

• Standing assignments:
  
  1. If any aspect of the current text reading is unclear or puzzling to you, come to class prepared to raise appropriate questions.  (Questions may also be submitted to the instructor by e-mail.)
  2. Report on recent literature.
     
     1. Regularly scan the current journal racks in Morris Library (5th floor, northeast corner) to identify articles of interest to you that involve issues related to evolutionary biology.
     2. Prepare a brief written report (200-500 words) which summarize one article published within the past six months and explain its relevance to particular problems in evolutionary biology.  [For guidance preparing written assignments, see The Writing Handbook.]
     3. Your goal in writing these reports is to convince your professor that you have read the article, thought about it, and appreciated why it is interesting and how it relates to course content.
     4. Include with the written report a complete citation of the article (authors, year, article title, journal title, volume and pagees) and reference to specific pages of the course textbook.
     5. This exercise may be completed as often as you wish, but no more than one report will be accepted for credit in any given week.

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Old assignments for prior test periods.

• Week 1 (due Jan. 25).
  Complete the Class Survey and Pretest, following instructions given in class.
  
• Week 2 (due Feb. 1).
  
  • Answer questions 2, 3, and 4 at the end of Ridley Chapter 1 (p. 20).
  • See the study and review questions at the end of Ridley Chapter 2 (p. 39).
    Define the terms in question 1.
    Answer (vi) and (vii) in question 2, showing your work (e.g., give a Punnett square).
    CORRECTIONS.
• Week 3 (due Feb. 8).
  
  • Chapter 3:  Think about all questions.  Answer question 6.
  • Chapter 4:  Answer questions 2, 3, and 4 (also, think about 5, and 6)
• Week 4, no assignment (EXAM on Friday, Feb. 12).
• Week 5 (due Feb. 22).
  
  1. Answer all questions at the end of Ridley Chapter 5 (pp. 131-132).
     Beware of careless editting in the text.  See notes below.
  2. Sketch a graph of the data in Table 5.4 (p. 102), with gene frequency vs. time.
  3. Sketch a graph of genotype frequencies at birth vs. time for this data.  (You may calculate the genotype frequencies yourself, or estimate them from Figure 5.2, p. 96.)
  4. Recommended: Make up additional problems for yourself, to practice these concepts.  For example:
     • Calculate and plot gene and genotype frequencies for selection against the dominant phenotype (after deriving the recurrence equation for Question 9 on p. 132).  Compare with graphs of from Table 5.4 data showing selection against the recessive phenotype.  What differences do you observe?
     • For selection coefficients and initial gene frequencies of your choice, calculate how many generations of selection it would take until the selected-against allele has a frequency lower than some target (e.g., 0.001).
     • Calculate what selection coefficient would be needed to reduce the frequency of a deleterious dominant (or, recessive) allele from 0.99 to 0.01 in 100 generations.
     • If the actual calculation for these examples appears onerous, at least consider how to formulate the problem so that you could do the calculation.

• Week 6 (due Mar. 1).
  
  1. Understand the answer to Study and Review Question 1, p. 149.
  2. Answer Study and Review Questions 3 through 6, pp. 149-150.
     Make sure you understand the answers (don't just copy them from the back of the book).
     As always, beware of careless editting in the text.  In Question 3, the rows of the table should be labelled (a), (b), (c) and (d).  Answer 3.(c) should be 0.375, not 0.625.

• Week 7 (due Mar. 8).
  
  • Review the Pretest, and complete question set B.  (If you kept the written copy, this is question set 2, A through H).
  • Answer Study and Review Questions for Chapters 7 and 8.
    (No problems noticed yet, although the wording for Question 7 on page 194 is a bit unclear.  Try, "A ratio comparing silent sites to replacement sites can be calculated for heterozygosity and also for rate of evolution.  If evolution takes place by neutral drift, what is the expected relationship between these two ratio?  This problem comes from section 7.14.  Hint:  How is each ratio related to mutation rate?  For rate of neutral evolution in terms of mutation rate, see section 6.4, p. 140.  For heterozygosity in terms of mutation rate, see Equation 6.7, p. 146.)
  • Remember, it is all right (and probably valuable) to look at the answers in the back of the book. However, the job for these exercises is not to copy down correct answers, but to discover whether you understand the material well enough to produce the answers yourself.
  • We will not do numerical problems for Chapter 9, but you might want to look over the questions ahead of time.  (There may be numerical errors in the back-of-the-book answers.)

• Week 8, no assignment.
  • EXAM on Friday, Mar. 12).

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CORRECTIONS to Ridley Chapter 2 "Study and Review Questions"

2 February.
The back-of-the-book textbook answers to problems 2(vi) and 2(vii) are not correct.
I currently believe that the simplest correction is to alter the problems.  If you work the problems as revised below, the back-of-the-book answers should be more satisfactory.

• (vi) Same as text EXCEPT loci are tightly linked (i.e, no recombination).
• (vii) Same as text, EXCEPT recombination occurs ONLY in the Ab/aB parent.
  (This is actually true for Drosophila,since crossing over does not occur in the male fruit fly.)  Now the back-of-the-book answers are closer, but still not quite right (the two homozyous genotypes should be r/4 instead of r).

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CORRECTIONS to Ridley Chapter 5 "Study and Review Questions"

• Question 1. The table gives genotype counts, not frequencies, although frequencies are easily derived from the counts. gives

• Question 2. (a) The correct answer should be p² / (1 - sq²) (note the exponent).

• Question 4.  The "accurate" answer in the back of the book (p. 701) has a typo in the seventh decimal place.

• Question 7 only makes sense if "generation n" is taken to mean "generation 1" (or, alternatively, "generation 2" and "generation 3" are taken to mean "generation n+1" and "generation n+2".

• Question 8.  See the Glossary for a definition of assortative mating. You must assume for this question that mating is exclusively assortative based on phenotype.  The answer to (a) appears incorrect.  Certainly the aa genotype will increase at the expense of the heterozygote genotype, for the reasons noted, but there is no mechanism which would reduce the frequency of the A allele. Answers to (c) and (d) are listed as (c)(i) and (c)(ii).

• In Question 9, selection is against the dominant phenotype.  A "recurrence relation" is an expression like Equation 5.4.  The derivation of that equation, in section 5.6 on p. 100-101, was based on selection against the recessive phenotype.  This problem asks for a similar derivation but with selection against the dominant phenotype (i.e., with fitness 1 - s for both genotypes AA and Aa.

• In Question 10, p* must be understood as the equilibrium frequency for the deleterious recessive allele a (and NOT, as in most examples, as the frequency of the dominant allele) A.

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