Evolutionary Biology Spring 2011 Study Questions

EEB2245/2245W

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.

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Lecture 1 (Jan 20, 2011)

What is speciation?

What are three ways relationships among organisms can be depicted or described?

What is homology?

Explain how the Permian Mass Extinction had a large effect on the diversity of life on Earth. How did that extinction influence the diversity of life present on Earth now?

Describe three different patterns in the diversity of life that evolutionary biology seeks to explain.

Lecture 2 (Jan 25, 2011)

Give an example of the fit between an organism and its environment.

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

Suppose you observe that the average weight of squirrels on campus is greater than their average weight on Horsebarn Hill. Give an example in which this difference in weight is the result of an evolutionary change. Given an example in which this difference is not the result of an evolutionary change. Describe an experiment you could do to determine whether the difference is due to an evolutionary change or not.

What is the relationship between Mendelian genetics and population genetics?

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

In general terms, what genotype frequencies are expected under the Hardy-Weinberg equilibrium?

What happens to genotype frequencies in a population under Hardy-Weinberg equilbrium? What happens to allele frequencies?

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

Lecture 3 (Feb 3, 2011)

While studying anole lizards you observe that some lizards are more green in color (found mainly on tree leaves) while others are more brown in color (found mainly on tree trunks). In order for this phenotype to be an evolutionary change what must be the source of variation? How could you test to see the source of this phenotype variation?

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

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

Why does population size matter when studying population genetics?

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?)

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

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?

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.

Lecture 4 (Feb 8, 2011)

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

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?

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.

In the Continent to Island Migration model, it is assumed that the frequency of the continent allele, pc, stays the same. Why is this a reasonable assumption?

How can you calculate the allele frequency of an island population after 1 generation of migration?

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

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

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

What is the effective population size, Ne, and what is an ideal population?

Lecture 5 (Feb 10, 2011)

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

What are the different types of non-random mating?

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

What is the most extreme form of inbreeding?

How does inbreeding generally decrease fitness?

Inbreeding generally occurs in smaller populations. What other evolutionary change have we studied that also affects small populations more than large ones? How are they similar and how do the two differ on their affect genotype frequencies in the population?

There are many species of plants that are obligate selfers (they can only reproduce with themselves). Why do you think that this is a successful strategy for these plants? (Think about the effects of inbreeding and fitness)

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

How does inbreeding depression affect populations? Give an example of a real example of inbreeding depression.

Lecture 6 (Feb 15, 2011)

What are the 3 premises of the theory of evolution by natural selection?

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

What HWE assumption does natural selection violate?

Why is the relative number of offspring more important when considering an organism’s fitness than the absolute number of offspring?

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

Calculate the mean fitness of the population of flies we used in our example, and show that the change in allele frequency results in an increase in the mean fitness of the population. (Hint: you'll need to keep track of quite a few decimal places to see the effect.)

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

How do you calculate genotype frequencies and allele frequencies before and after selection?

What does w symbolize and how is it calculated?

How does natural selection counteract the effects of inbreeding depression?

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