Evolutionary Biology Spring 2015 Study Questions

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The following study questions are designed to help you think about the lecture material. They are not comprehensive questions. Exam material is NOT limited to the topics in study questions and will not follow this format.

Return to Evolutionary Biology webpage

Lecture 1 - Jan 20th 2015

1) What type of adaptation would you expect to see in an organism trying to survive in an environment with visual predators?

2) What’s one possible explanation for powered flight appearing only once in invertebrates and at least three times in vertebrates?

3) Why would it be advantageous for an organism to resemble something else; i.e. a caterpillar that looks like bird droppings or an orchid that smells like carrion?

4) What’s convergence? Can you think of an example we saw in lecture?

5) Do similar traits always evolve to solve the same challenges? For instance, are all brightly colored organisms just trying to get a mate?

6) In what ways can humans be a source of selection to other organisms?

7) What’s the difference between evolutionary change and phenotypic plasticity?

Lecture 2 - Jan 22nd 2015

1) Suppose you observe that the average weight of squirrels on campus is greater than their average weight on Horsebarn Hill. Describe how you would use a reciprocal translocation experiment to test the hypothesis that the difference in weight of squirrels on campus and on Hosebarn Hill is the result of an evolutionary change. Explain what outcome(s) would support this hypothesis. What outcome(s) would not support the hypothesis?

2) In class, we focused on figuring out how to tell if a phenotypic difference was caused by an evolutionary change. What if there's no phenotypic difference between two populations you observe in the wild--could there still have been an evolutionary change? Why or why not?

3) Why do we focus on genetic differences in studying evolutionary change?

4) What is the relationship between Mendelian genetics and population genetics?

5) What are the variables used to describe the genetic composition of a population?

6) In general terms, what genotype frequencies are expected under the Hardy-Weinberg equilibrium with 2 alleles? What do you think the proportions are going to be if we’re studying a locus with 3 alleles? Trying drawing one of those box diagrams we saw in class to support your answer.

7) What happens to genotype frequencies in a population under Hardy-Weinberg equilibrium in subsequent generations? What happens to allele frequencies?

8) Hardy-Weinberg practice: try the Pdficon small.gif problems here to get practice with describing the genetic composition of a population and determining Hardy-Weinberg proportions.

9) Challenge Problem: What’s the highest frequency of heterozygotes that is expected under HWE for a locus with 2 alleles?

Don’t forget to finish Activity 2 – It should be handed in at the beginning of lecture on Thursday Jan. 29th.

Lecture 3 - Jan 29th 2015

1) Why do we use allele and genotypes frequencies instead of the number of gametes or individuals in a population?

2) How many generations does it take for a population to establish genotype frequencies in HWE (Hardy-Weinberg equilibrium) given all the assumptions are met?

3) In what situation do we need to assume Hardy-Weinberg equilibrium instead of testing for it? What information do we need in order to test for HWE?

4) HWE assumes that there is no new genetic mutations. However, all new genetic variation occurs through mutation. Why do we mostly ignore this assumption violation?

5) You observe the genotype frequencies of a cow population for 2 generations. The allele frequencies and genotype frequencies do not change. Is this population in HWE? Why or why not.

6) What happens to genetic variation, allele frequencies, and genotype frequencies as a result of inbreeding?

7) What are the different types of non-random mating?

8) How can you tell the difference between inbreeding and assortative mating?

9) What is the most extreme form of inbreeding?

10) What do you expect the effects of inbreeding would generally be on fitness? Why?

11) Why are inbred lines of model organisms (e.g. Drosophila, mice, C. elegans) often used in biomedical research?

12) Under what conditions would assortative mating cause evolution? Under what conditions would it not result in evolution?

13) Given what you know about the different types of non-random mating and their effects on genotype and allele frequencies, what would you expect to be the result of disassortative mating?

There are very good practice questions at the end of each chapter of the textbook. Try doing questions 1 through 5 at the end of Chapter 9 - page 255

Lecture 4 - Feb 3rd 2015

1) Give an example of assortative mating in which mates are NOT chosen by the way they look. What other types of phenotypic characteristics can also be used to choose mates?

2) Assortative mating by size is very common in nature. Can you think of any explanation for why this type of preference arises so frequently?

3) What’s the Wahlund effect? How does it affect the genetic diversity of a population?

4) Is the pattern produced by the Wahlund effect more similar to that observed for inbreeding or assortative mating? How does it differ from that pattern?

5) Why does population size matter when studying population genetics?

6) What effect does genetic drift have on: (a) genetic variation (b) genotype frequencies (are they in Hardy-Weinberg proportions or not? Do they change from generation to generation?)

7) What does it mean when an allele has ‘been fixed’ or ‘gone to fixation’ in a population?

8) If an A allele has a frequency of 0.95 in a population, will this always fixed through drift? What is the probability the A allele will be fixed?

9) One of the consequences of small population size is a tendency to mate with close relatives. What other evolutionary change have we studied that also affects small populations more than large ones? How are these processes similar and how do the two differ on how they affect genotype frequencies in the population?

10) What’s the effect of genetic drift in the genetic diversity of individuals belonging to the same population? How about on individuals belonging to different populations?

11) Given what you know about genetic drift, what’s most likely to happen to a new mutation in a small population? How about in a large (infinite) population?

Lecture 5 - Feb 5th 2015

1) Which assumption of the HWE do both mutation and migration violate and why?

2) What is migration in an evolutionary sense and why is it important for understanding evolution in populations? Give an example of migration and explain its effects on allele frequencies.

3) Why is it important to consider the effects of migration and drift together?

4) How many migrants does it take to keep populations from diverging? Why is this the same for small and large populations?

5) What factor(s) affects the rate of homogenization of allele frequencies when populations are connected by migration?

6) How does inbreeding depression affect populations? Can you think of a real example of inbreeding depression?

7) What level of genetic diversity do we expect to see in a population that has been through a bottleneck? What evolutionary forces are at play in this case? If nothing changes, what’s the ultimate fate of this population?

8) Imagine you are hired by the US government to take part in a conservation effort as a consultant. What aspects of a population’s structure do you have to consider in order to maximize maintenance of genetic diversity? How would you explain to government representatives why it is crucial to maintain genetic diversity?

9) What’s the impact of habitat fragmentation on genetic diversity? What are the evolutionary processes that contribute to that scenario?

Lectures 6 & 7 - Feb 10th and 12th 2015

1) What are the premises of the theory of evolution by natural selection?

2) What is the difference between natural selection and evolution by natural selection?

3) What is artificial selection? Give examples of organisms that have been artificially selected.

4) What do evolutionary biologsts mean when they talk about the fitness of an individual?

5) What HWE assumption does natural selection violate?

6) How do natural selection and genetic drift affect phenotypes? Give an example of when genetic drift and natural selection could be acting on a population.

7) Imagine one of your family members is really curious about what you are learning in this class. How would you explain to him/her how natural selection increases the frequency of an advantageous trait in a population?

8) Can natural selection act on a population with very little genetic diversity (most loci have one fixed allele)?

Lecture 8 - Feb 17th 2015

1) Thinking about the examples of natural selection in action we saw in lecture, what’s the source of selection pressure for the guppies? How about for the Darwin finches in the Galapagos?

2) How do we know the increase in bill depth in the Darwin finches example is a result of evolution by natural selection instead of genetic drift?

3) Can evolution happen from one generation to the next? In order words, can evolution happen in a short period of time?

4) Why do organisms have to be constantly changing in order to increase (or maintain) their fitness? How come different phenotypes can be the fittest in different geographical areas or at different points in time?

5) What are the three modes of natural selection? What’s the evolutionary consequence of each of them and how are they affected by initial allele frequency?

6) What is Fisher’s Fundamental Theorem and why is it important?

7) What does w symbolize and how is it calculated?

8) If the most fit genotype is the heterozygote, why does natural selection lead to the decrease of heterozygotes in the entire population?

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