Download Study Questions for Exam 1 Biology 354 Lecture 1: Natural selection

Study Questions for Exam 1
Biology 354
Lecture 1: Natural selection
What are Darwin’s four postulates?
What would figure 3.10 look like if bill depth was variable but was not heritable?
Big billed birds seemingly survived better, presumably because they were better able to eat large
seeds during the drought. A recent study measured biting strength of these finches. Predict
whether and bite strength increased with bill size.
What appears to be the developmental basis for differences in bill size?
What is a selection differential, and how does one measure it? What is the selection differential
under stabilizing selection?
Be able to draw and interpret “Schluter graphs” for directional, stabilizing, truncation, and
disruptive selection.
Kingsolver et al.’s study reviewed the strength of directional selection in nature. What did they
find, and what does this tell you about selection in most organisms and in most years?
The Grant-team study was descriptive, but sometimes one can do manipulative studies. For
example, Barry Sinervo wanted to test whether survival was positively related to hatchling size
in lizards. What was his manipulation? Why was such an experiment useful? How would you
control for the effects of the “surgery”?
Darwin relied heavily on examples of “artificial selection” (e.g., with dogs, chickens, grain yield)
in building a case for the power of evolution by natural selection. Why did he do so?
How does “laboratory natural selection” differ from “artificial selection”?
Lecture 2: Adaptation
Define adaptation (from an evolutionary perspective)? Why might the selective factor that led
to the origin of a trait differ from the factor that maintains it today?
In the example of IR pits of certain vipers, what did biologists initially think about the adaptive
significance of this trait? After Krochmal & Bakken’s work, what do they think now? Does the
adaptive significance of the pit fit within Platt’s concept of a “crucial experiment”?
What is the Panglossian Fallacy? Why should someone beware of committing this fallacy?
Some people believe that traits are perfectly adapted. Why are some traits less than perfectly
adapted? Do some traits have no adaptive function? Can you name one?
The Brodies (father & son) showed that some garter snake populations have evolved the ability
to eat toxic newts. Do resistant garter snakes suffer a cost?
Invasive species offer the opportunity to monitor rates of evolution in nature. The text describes
a case of the soapberry bug (p. 36 & 38). The bug itself wasn’t introduced, but a new food plant
was. How did the bugs respond evolutionarily to the new plant? What experiment could you do
to test the hypothesis that the change in beak length was causally related to the new fruit?
Lecture 3: Life History Evolution
What is the Principle of Allocation? Who first coined the term?
What are the advantages and disadvantages of reproduction early in life? Draw a single graph
showing how fitness changes as a function of age at maturity for a population that experiences
heavy mortality versus one that experiences low mortality (thus, two lines on one graph).
What is Lack’s Hypothesis for optimal egg size? What are the assumption of his hypothesis?
Draw a graph of fitness of a mother lizard as a function of the size of her egg, for the case in
which fitness of her offspring is inversely related to their egg size.
Why is aging an evolutionary paradox?
Why does the force (effectiveness) of selection decline with age? What are the two major
evolutionary theories of aging? How do they differ?
Imagine that you took opossums from the mainland of Georgia and from Sapelo Island and
raised them in the laboratory from birth to death. You monitored their survival patterns and
found that they were the same – in other words, they died at the same rate. How would this
cause you to reinterpret figure 12.14a in the text?
Lecture 4: Sexual Selection
Males and females often differ in body size. Explain how this might evolve by natural selection,
or by sexual selection. How might you test which explanation was correct?
Explain why a trait (e.g., flashy tail of peacocks) can evolve even though it is likely opposed by
natural selection.
Why is there an asymmetry in sexual reproduction for males versus females? What is meant by
variance in reproductive success? How do males and females differ in the variance of
reproductive success? What is the major behavioral consequence of reproductive asymmetry?
What is male-male competition, and what are the two basic processes involved?
How does body size influence mating success of male marine iguanas in normal years, and in
years with limited food? Do you see parallels with patterns of selection on Galapagos finches?
What is sperm competition? Speculate on the volume of ejaculates from males from a
monogamous species versus a polygamous species.
If new males take over a lion pride, a pregnant female will often spontaneously abort her fetus.
What is the benefit to the male? Is this beneficial to the female?
Why to alternative male mating strategies evolve? Give an example of such a strategy.
What is female choice (as regards sexual selection)? In the case of peafowl, females prefer
males with long tails. Why?
In the case of the hanging fly, what is the pattern of selection on prey size from the male’s
perspective?
What is the “sexy son” hypothesis? If a female prefers and mates with a “flashy” male, what
will her sons be like, and what will her daughters likely prefer?
Lecture 5: Hardy-Weinberg & Drift
What is the theory of blending inheritance and why was it a challenge to Darwin’s hypothesis?
Given a set of genotype frequencies, be able to estimate the gene frequencies in that generation,
and both the genotype and gene frequencies in the next generation. In the absence of selection,
migration, etc., are genotype and gene frequencies stable from generation to generation?
Graph how the frequency of heterozygotes changes as a function of the frequency of one allele.
Imagine you observed gene frequencies of A = 0.4 and a = 0.6. What are the expected genotype
frequencies if Hardy-Weinberg holds? Imagine that you measured genotype frequencies and
found, AA = 0.4, Aa = 0.4, and aa = 0.2. How might you interpret your results?
How does drift vary with the size of the breeding population? Draw a graph of how the standard
deviation in frequency of a gene changes with population size. What does this graph tell you
about drift?
In finite populations with no selection, mutation, or gene flow, what will happen to allele A in a
population that starts off with A at a frequency of 0.5 (or at a frequency of 0.7)?
Invasive species often go through bottlenecks. What is the genetic consequence? How might
this reflect their rate of evolution in a new environment?
Lecture 6: Factors influencing genetic constitutions of populations
Draw a graph of the frequency of an allele A versus time for two cases: 1) A is strongly
selected against or 2) A is weakly selected against. Assume the starting frequency of A = 0.9,
and assume no dominance.
What is frequency dependent selection?
What is a mutation-accumulation experiment? What do they tell us about mutations?
What is the evidence from Rich Lenski’s experiments that mutations are sometimes beneficial?
What is meant by saying that there’s a balance between mutation and selection? What is
“balanced”?
In the example of water snakes around Lake Erie, most mainland snakes were all banded, except
a population on the peninsular mainland. Derive two hypotheses for why those particular snakes
have some unbanded morphs.
What is the impact of inbreeding on the frequency of various genotypes? Be able to show
(mathematically) what happens to the frequency of heterozygotes.
Why should close relatives abstain from having children with each otehr?
If you were asked to save an endangered population, which had a very small sample size, what
would be your genetic concerns?