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Name & SS# Seat #
BIOLOGY 54 DR. REICE
MIDTERM EXAM OCTOBER 1, 1996
WRITE ALL OF YOUR ANSWERS ON THE QUESTION SHEET. THIS EXAM HAS 100
POINTS. BUDGET YOUR TIME.
1. THE NICHE (10 points): What is Grinnell's model of the niche? (2 pts).
Name Hutchinson's model (2 pts). Compare and evaluate the two
models (4 pts). For one real species, illustrate each concept of
the niche (2 pts).
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2. SPECIES PACKING: Two species with nearly identical niches
commonly coexist in Nature. If both species are found in the same
habitat, what can account for their coexistence. Give two different
explanations. Illustrate with examples using real species. (10 points)
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3. BIOMES: (10 points)
A. As you climb up Clingman's Dome in the Great Smoky
Mountains National Park, you climb out of a deciduous forest
and into a boreal forest biome. Explain why. (6 points)
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B. What distinguishes the tundra from a desert? (2 pts) What is
the critical feature of the tundra which distinguishes it from all
other biomes? (2 pts)
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4. State the Fundamental Theorem of Natural Selection.
(2 points, 5 points total)
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Who wrote it?_________________________________(1 points)
What makes it "fundamental?" (2 points)_____________________________________
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5. Define a species. (5 points)
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6. ALLELIC AND GENOTYPIC FREQUENCIES (5 points) Tay-Sachs
disease results in mental illness and blindness with death by age four.
It is caused by homozygosity for a recessive allele (t). It is most
common in Jews of Eastern European origin. In one population the
condition occurs in 1 out of 90,000 newborns. Calculate the
allelic frequencies. If there is random mating, what are the expected
frequencies of the three genotypes at birth?
F(T) = p= ____________
F(t) = q= ____________
Under random mating F(TT) = ____________ F(Tt) = ____________ F(tt) = ____________
7. HARDY WEINBERG AND RELATIVE FITNESS. (10 points)
A genetic screening program of blood types in Alaska found
the following data:
Genotype Frequency
MM = 13550
MN = 6400
NN = 50
Is this population in Hardy-Weinberg equilibrium? Show all
your work.[Hint: Critical value for Chi square test with
df=1 is 3.84, and for df=2 is 5.99 for P<0.05] (7 points)
Is selection operating in this population? What does the
data tell you about the relative fitness of the three
genotypes? (3 points)
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8. MUTATION RATES (10 points): A population has
allele B1 which mutates to B2 at a rate of 5 x 10-4
and back mutates at a rate of 5 x 10-6 from B2 to
B1. What are the equilibrium gene frequencies of
B1 and B2? (4 points)
Will one allele ever become fixed? ________________________(1 point)
Why or why not?(2 points)___________________________________________________
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Why does point mutation alone rarely change gene frequencies
in a population? Which forces combine with mutation can
result in major shifts in gene frequencies? (3 points)
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9. INBREEDING (10 points): Define Inbreeding Depression.
Contrast with Heterosis. (4 points)
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Calculate the coefficient of inbreeding the children of a marriage
between first cousins. Chart the family and the gene flow. (4 points)
Does inbreeding change gene frequencies?(2 points) _________________
10. NATURAL SELECTION AND RELATIVE FITNESS (10 points
total) Use the following table to select the correct formula and
calculate the solution. Show all work.
A population of mallard ducks has an allele w which allows
water to wet their outer feathers and causes them to swim
very awkwardly. It is expressed only in the homozygous
recessive (ww). The homozygous dominant, WW, and
the heterozygous individuals have normal feathers.
The genotypes are: WW Ww ww
1. Parental zygotic frequency 1000 40 20
2. Zygotes produced in next
generation 2000 80 10
3. Relative Fitness
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What is the relative fitness of each genotype (fill in table)? (3 points)
What is the value of s, the selection coefficient. (1 points) s = ________
Which selection model applies?________________________ (1 point)
What will the change in F(w) be in the next generation? (3 points)
What will be the new values of p and q? (2 points)
p = _______ q = _______
11. Define Genetic Drift. How and why does genetic drift work
to change gene frequencies? (10 points)
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12. A population's size is 1000, and the rate of migration,
m= 0.001. Will migration or drift be the predominant force
altering gene frequencies in this population? Explain the
reasoning behind your answer. (5 points)
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Honor Code Pledge_____________________________________________________________
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