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Name Student Number Seat #
BIOLOGY 54 SECTION 007 DR. REICE
SECOND MIDTERM OCTOBER 31, 1996
1. Speciation (12 points)
Speciation occurs in several stages. Identify and explain the 2
main stages of speciation. (4 points)
Stage I.___________________________________________________________________
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Stage II.__________________________________________________________________
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Allopatric speciation requires___________________________________________(2 points).
Sympatric speciation can be the result of behavioral, ecological
and genetics mechanisms . Give a real world (actual) example of
each type and explain how it works.( 6 points)
Behavioral_____________________________________________________________________
Ecological_____________________________________________________________________
Genetic_______________________________________________________________________
2. Heritability is defined as the ratio of ___________________ variation to
______________________ variation. It measures the relative contribution
of ______________________ and _______________________ to the
determination of the phenotype of an individual. (4 points)
3. Life Tables (14 points)
A population of NC Brown Shrimp is sampled every six months for
3 years. The number of survivors from a marked cohort is as follows:
Age Number alive lx
0 2000
6 mos. 200
1 year 100
18 mos. 80
2 years 60
30 mos. 30
3 years 0
Calculate lx for all ages x and plot the graph below. (6 points)
What type of survivorship is this?________________ (2 points)
What accounts for the shape of the curve? (2 points)
____________________________________________________________________________
Plot graph here:
What is the life expectancy of 2 year old shrimp? (Hint: translate
the number of time steps into months yet to live). Show your
necessary calculations by constructing and filling in the table
above. (4 points)
4. Population Growth (18 points)
A population of rabbits has the following survivorship.
Calculate the mx table using the following information. Rabbits
begin breeding at age 2. 2-year old rabbits have 4 bunnies per
female, while 3, 4 and 5 year old rabbits have 10 cute little
bunnies per female. The sex ratio is
50:50. (3 points)
Age lx mx
0 1.0
1 0.90
2 0.80
3 0.40
4 0.20
5 0
Calculate the net reproductive rate (3 points)_________________
What is the generation time? (3 points)__________________________
What is the intrinsic rate of natural increase? (3 points)
___________________________
Is the population growing? (1 point) __________________
How do you know? (2 point)_______________________________________
Explain the difference between the Net Reproductive Rate and
the Intrinsic Rate of Natural
Increase. (3 points)____________________________________________________________
____________________________________________________________________________
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5. Logistic Growth (14 points)
Write out (3 points) and plot (3 points) the logistic model of
population growth. Define all terms.
List and explain 3 strengths and 3 weaknesses of this model.
Be concise. (6 points)
Strengths:___________________________________________________________________
___________________________________________________________________________
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Weaknesses:__________________________________________________________________
____________________________________________________________________________
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In your opinion, explain why you think we should or should not
continue to use this model. (2 pt)
____________________________________________________________________________
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6. Life Histories (6 points)
Give a way to reduce the world's human population growth, without
compelling 2 children per family. (2 points)
____________________________________________________________________________
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What kind of environment favors iteroparity?______________________________(2 points)
What is the relationship between numbers of offspring per litter and
parental care? (2 points)
____________________________________________________________________________
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7. Competition (20 points)
Write out and define all terms of the Lotka-Volterra Competition
Model (6 points).
In addition to the strengths and weaknesses identified for the
logistic model, what additional strengths and weaknesses
can you identify. (4 points)
____________________________________________________________________________
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Give an example of interspecific resource competition_________________________________
_________________________________________________________ (2 points)
What is the competitive exclusion principle?________________________________________
______________________________________________________________________________
_______________________________________________________________(2 points)
What type of competition is important to Natural Selection?_____________________________
(2 points)
Two species have adjacent but non-overlapping ranges. How can
you be sure that the distribution is due to competition?(4 points)
____________________________________________________________________________
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8. Predation (8 points)
Give two examples of plant defenses against predators. (2 points)
____________________________________________________________________________
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Give two examples of animal defenses against predators.(2 points)
____________________________________________________________________________
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What is the advantage of mass cropping? (2 points)
____________________________________________________________________________
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What makes parasitism similar to and different from predation? (2 points)
____________________________________________________________________________
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9. Symbioses (6 points)
Compare and contrast commensalism and obligate mutualism.
Give a real world example of each. (6 points)
____________________________________________________________________________
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Honor Code Pledge:_________________________________________________________
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Signature_________________________________