This document appears to be a practice exam for a biology course covering topics related to population ecology. It consists of 25 multiple choice questions testing understanding of concepts like logistic growth, carrying capacity, natural selection, kin selection, and other population dynamics principles. The questions cover a range of difficulty levels and topics commonly addressed in an introductory ecology course.

1. BIOL 1404 Spring 2012
Dr. McGinley
Retest- First Midterm Exam
Choose the best answer for each question. (2 points each) Good luck.
1. Animals that help other animals of the same species
(a) have excess energy reserves
(b) are bigger and stronger than the other animals
(c) are usually related to the other animals
(d) are always male
(e) have defective genes controlling their behavior
2. In Belding’s ground squirrels, it is mostly the females that behave altruistically by sounding
alarm calls. What is the most likely reason for this distinction?
(a) males have smaller vocal chords are are less likely to make sounds
(b) females invest more in foraging and food stores, so they are more defensive
(c) females settle in the area in which they were born, so the alarm is warning kin
(d) the sex ratio is biased
(e) males forage in areas separate from females: therefore, alarm calls are useless
3. As N approaches K for a certain population, which of the following is predicted by the logistic
growth equation?
(a) the population growth rate will not change
(b) the population growth rate will approach zero
(c) natural selection will occur in the population
(d) the population size will increase exponentially
(e) the carrying capacity of the environment will increase
4. Why do populations grow more slowly as they approach their carrying capacity?
(a) density dependent factors lead to fewer births and increased mortality
(b) density independent factors lead to fewer births and increased mortality
(c) hormonal changes promote higher death rates in crowded populations
(d) individuals voluntarily stop mating so that overcrowding does not occur
(e) the incoming energy decreases in populations experiencing a high rate of increase
5. During exponential growth, a population always
(a) grows by thousands of individuals
(b) grows at its maximum per capita growth rate
(c) quickly reaches its carrying capacity
(d) cycles through time
(e) loses some individuals to emigration

2. 6. Evidence suggests that some grass species benefit from being grazed. Which of the following
terms would best describe this plant-herbivore interaction?
(a) mutualism
(b) commensalism
(c) parasitism
(d) competition
(e) predation
7. Which of the following relationships between trait size and fitness would lead to directional
selection?
(a) a positive relationship between trait size and fitness
(b) a negative relationship between trait size and fitness
(c) organisms with intermediate trait sizes have higher fitness than organisms with
extreme traits
(d) organisms with intermediate trait sizes have lower fitness than organisms with
extreme traits
(e) a and b
8. Which of the following altruistic traits is unlikely to be explained by reciprocal altruism?
(a) food sharing among unrelated hyenas
(b) a male buffalo sacrificing his life to protect an unrelated individual
(c) sterile workers in bees
(d) female birds helping their sisters to raise their offspring
(e) none of the above
9. Which of the following is an example of a benefit of sex?
(a) females that mate with the “best males” produce higher quality offspring
(b) females reproducing sexually pass on twice as many genes as they would while
reproducing asexually
(c) offspring produced by sexual reproduction have better chances of survival in a
changing environment
(d) there is no genetic variation produced during sexual reproduction
(e) none of the above
10. Which of the following are required to select for antibiotic resistant microbes?
(a) there is a genetic basis for resistance to antibiotics
(b) there is variation in mortality of microbes treated with antibiotics
(c) patients fail to finish their antibiotic prescription
(d) a and b are required
(e) all of the above are required

3. 11. Which of the following represent an indirect interaction between species?
(a) female elephant seal preferring to mate with the largest male
(b) a kangaroo and a sheep competing for grass
(c) a plant releasing an allelopathic chemical
(d) a harvester ant feeding on a seed
(e) none of the above
12. What would I ask you to make you draw the j-curve?
(a) how does the population growth rate vary over time in exponential growth?
(b) how does the population size vary over time in logistic growth when the initial
population size is equal to the carrying capacity?
(c) how does the population growth rate vary over time in logistic growth when the initial
population size is much larger than the carrying capacity?
(d) how does the population growth rate depend on population size in exponential
growth?
(e) none of the above
13. Which of the following are true in populations when their population size is smaller than the
carrying capacity?
(a) B/N > d
(b) r < 0
(c) dN/dt < 0
(d) b and c are true
(e) a, b, and c are true
14. Which of the following correctly rates the stages of the demographic transition from the
highest to the lowest population growth rates?
(a) pre-industrial > transitional > post-industrial
(b) post-industrial > transitional > pre-industrial
(c) transitional > pre-industrial > post-industrial
(d) transitional > post-industrial > pre-industrial
(e) transitional > pre-industrial = post-industrial
15. Which of the following population have the highest population growth rate is they are
undergoing logistic growth with a maximum per capita growth rate of 2 individuals per year per
individual?
(a) N = 1 individual
(b) N = 10 individuals
(c) N = 100 individuals
(d) N = 1000 individuals
(e) this question cannot be answered with the information provided

4. 16. According to Hamilton’s Rule, should a male prairie dog give a warning call that increases
his chance of dying by a factor of three and increases the chance of survival of all recipients by a
factor of two if he can help two sons, one daughter, and one niece?
(a) yes, the prairie dog should be altruistic and give a warning call
(b) no, the prairie dog should be selfish and not call
(c) Hamilton’s Rule would not apply in this situation
(d) this question cannot be answered with the information provided
17. Proposed benefits of sexual reproduction include
(a) producing genetically variable offspring increases the chance of success when the
future environment is unpredictable
(b) producing genetically variable offspring increases the effectiveness of transmission of
genes from parents to offspring
(c) producing genetically variable offspring decreases the chance that a single microbe is
able to infect and kill an entire genetic lineage
(d) a and c
(e) a, b, and c
18. Some male fruit flies release toxic seminal fluids that act as an “anti-aphrodesiac” and
makes females less likely to want to mate with another male. Which of the following best
explains this interesting trait?
(a) sexual selection
(b) natural selection
(c) female choice
(d) best genes
(e) male-male competition
19. Which of the following observations would best support the hypothesis that females choose
to mate with males with the most extreme traits because of the sexy sons hypothesis? Females
who mate with males with the most extreme traits produce
(a) sons that are better at finding food
(b) sons and daughters that are better at resisting disease
(c) sons that are better at attracting mates
(d) daughters that are better at attracting mates
(e) c and d
20. Which of the following intraspecific interactions bests describes the production of
allelopathic chemicals by plants?
(a) mutualism
(b) parasitism
(c) exploitative competition
(d) herbivory
(e) none of the above

5. 21. Which of the following best describes the graph that shows how the population growth rate
depends on population size in exponential growth?
(a) over time the population size increases
(b) as population size increases the population growth rate increases at a constant rate
(c) as the population size increases the per capita growth rate increases at a constant rate,
r
(d) over time the population growth rate increases to a maximum and then decreases to
zero
(e) the population growth rate is independent of population size in exponential growth
22. In a population of 50 individuals in one year 5 individuals are born and ten individuals die.
What is dN/dt in this population?
(a) 5 births per year
(b) 5 individuals per year
(c) 0.1 individual per year per individual
(d) dN/dt = rN
(e) none of the above
23. Which of the following are always true?
(a) human populations increase in size over time
(b) females prefer to mate with the male with the “best genes”
(c) B - D = rN
(d) all of the above are always true
(e) neither a, b, or c are always true
24. Which of the following best describes b?
(a) it measures the birth rate
(b) it measures the per capita birth rate
(c) it measures the number of births in a population per time
(d) it measures the number of births per female per time
(e) it measures the number of births per individual per time in a population
25. Which of the following hypotheses can be used to help understand examples of altruism in
humans?
(a) cultural selection
(b) kin selection
(c) sexy sons hypothesis
(d) a and b
(e) neither a, b, or c could explain examples of altruism in humans

6. 26. Imagine that you have been hired to advise an organization in a developing country interested
in decreasing patterns of human population growth in their region. Which of the following
would be effective strategies to implement to slow population growth?
(a) establish a nutrition program for expecting mothers to increase the birth weight of
their babies
(b) increase educational opportunities for children in the region
(c) establish local health clinics to reduce mortality caused by infectious diseases
(d) b and c
(e) a, b, and c
27. In models of exponential population growth
(a) the population growth rate slows dramatically as N approaches K
(b) new individuals are added to the population most rapidly when N << K
(c) the per capita growth rate is constant
(d) the population growth rate is constant
(e) c and d
28. Vampire bats feed each other by regurgitating blood. Studies have shown that vampire bats
are likely to die if they do not obtain a blood mea. at least every other day. Individuals who have
behaved altruistically in the past are helped by others in the future. However, there is no
evidence that a previously non-altruistic bat is refused help when it requires it. Most instances of
feeding happened between individuals of the same group, who are on average cousins. Which of
the following hypotheses best explains the food-sharing habits in vampire bats?
(a) kin selection
(b) reciprocal altruism
(c) cultural selection
(d) a and b are equally likely to explain this altruistic behavior
(e) a, b, and c are equally likely to explain this altruistic behavior
29. In a population of elephant shrews, in one year 10 individuals are born and 12 individuals
die? Which of the following population biology parameters can you calculate using this
information?
(a) b
(b) the per capita growth rate
(c) population growth rate
(d) r
(e) c and d
30. Which of the following are examples of interference competition?
(a) a male beetle mating with a female
(b) a male bison “guarding” a female so that so one else can mate with her
(c) a polyandrous female attracting a male using bright coloration
(d) a and b
(e) neither a, b, or c

7. (20 points) Answer questions a & b on in the space provided on the front of this page. You may
use the remaining space on the front page and the back of the sheet for question c.
a) Draw the graph that shows how the population growth rate varies over time in logistic growth
when the initial population size is much smaller than the carrying capacity.
b) describe, in words, all of the information held in the graph you drew in part a
c) Diagram the demographic transition and explain why patterns of population growth are so
different between developed and developing countries.

8. (20 points) You may use both sides of this sheet.
Why, at first glance, is the production of altruistic acts difficult to understand? Discuss three
possible hypotheses to explain the production of altruistic traits.