BIO 160 General Ecology Midterm II (100 pts) Name______________________________

Multiple Choice (3 pts ea, 30 pts):

1. Suppose you have photoidentified 30 humpback whales around the island of Oahu in one cruise around the island. Two weeks later you return to the same area and photograph all the whales you encounter. On the second trip you photograph a total of 50 whales, of which 10 were photographed previously. Using the Lincoln-Peterson index with the Bailey correction, estimate the number of humpback whales around Oahu during your study.

a. N = Mn/m = 30 *50/10 = 150 (approx)

b. N = Mn/m = 50*10/30 = 17 (approx)

c. N = M(n+1)/(m+1) = 50(11)/31 = 18 (approx)

d. N = M(n+1)/(m+1) = 30*51/11 = 139 (approx)

e. N = mn-M + bailey = 10*50-30 + 17.44 = 487


2. In lecture I introduced the yellow flowers of the genus Encelia and mentioned that E. californica is restricted to a band along the coast and E. actoni lives in the Mojave desert. There are two other species with overlapping ranges that include parts of southern California, Nevada and western Arizona. These species live in a very hot environment. E. fruticosa inhabits slopes that are severely limited in water and has adaptations for dealing with desert conditions very similar to that of E. actoni. On the other hand E. frutescens is adapted for desert life by

a. having highly pubescent leaves and stems that reflect 60% of incoming sunlight.

b. living in ephemeral stream channels and relying heavily on evaporative cooling

c. growing only in the shade of giant saguaro cacti

d. encouraging heavy browsing by desert herbivores leaving only the roots to live successfully in the cool dark soil

3. Interior old-growth redwood and Douglas fir forests are important as nesting habitat for spotted owls. Significantly greater nesting success and fledging success occur in old growth forests than in any other habitat type. If these are absolute facts but a scientist carefully conducts an ecological survey, runs a statistical test comparing mean nesting success in old-growth forests vs. clearcut patches and fails to reject the null hypothesis that there is no difference, what type of error was likely committed?

A. Type I C. a error

B. Type II D. P level

4. Clonal growth is a form of _________ reproduction.

A. Asexual

B. Parthenogenetic

C. Haplodiploid

D. Sexual

5. Assuming that you have an altruistic gene, the probability that you share that gene with a cousin is:

A. 0.125

B. 0.25

C. 0.50

D. 0.875

6. Okay, you've been hired as a botanist for the State and your first job is to determine the size of the Arctostaphylos myrtifolia population. You go out to the 1 km x 1 km (hypothetical) reserve in which all known plants are located and you make the following counts within randomly-located 1 square meter frame quadrats (3, 3, 4, 5, 4, 4 ,5, 3, 5). Most likely population size is:

A. 4 x 104 plants

B. 36 plants (Hint:N=DA)

C. 3.5 x 104 plants (D=x/sample area)

D. 4 x 106 plants

7. Elephants have a potential life span of over 75 years, are very slow to mature, produce few offspring and protect their young from predators by keeping them to the inside of the herd. Which of the following survivorship curves would be most likely to represent an elephant population (y axis = log of number surviving; x axis = age or time)?

A. B.

C. D.

8. You have been studying the population dynamics of a certain species of insect with non-overlapping generations and each time you plot growth from low numbers to a stable equilibrium you observe the following general pattern over time:

This tells you that ro (the intrinsic per capita growth rate) is:

A. greater than zero but less than one

B. greater than one but less than two

C. greater than two but less than 2.8

D. greater than 2.8

9. Which of the following values for r and RO indicate that a population is shrinking

a. RO > -1 r > 0

b. RO < 1 r < 0

c. RO < 0 r < 1

d. RO < ln l r < l

10. Many marine organisms settle out from the water column as spores or larvae, attach themselves to rocks and begin to grow occupying greater and greater space. This exemplifies which types of competition

a. Encounter and Consumptive

b. Preemptive and Overgrowth

c. Chemical and territorial

d. Consumptive and Encounter

Short Answer (3 pts ea; 39 pts)

11. Match the following data sets with the appropriate statistical test

You have count data for several species of ducks using 4 different ponds, your question is: Are the species counts at each pond significantly different from counts expected if ducks are distributed by chance alone?


You have rain-gauge data and mosquito densities obtained from sweep net surveys for a meadow in the Sierra Nevada. You want to determine if there is a statistically-significant relationship between mosquito abundance immediately after it rains and the amount of rain that falls.


You want to see if there really is a significant difference in the amount of time it takes for a honey badger to find a bees nest with and without the aid of a honeyguide. You have two sets of data: times for unaided and times for aided. From these data you obtain two means, now you want to determine if the means are significantly different.


Options: Pierson's t-test ANOVA Natural log Regression Correlation

Shannon-Weaver MANOVA Excel2000 X2 RMS

12. Give two examples of density dependent factors and one example of a density independent factor that might limit populations of insects.

density dependent factors_________________________________________________________


density independent factor_________________________________________________________

13. ___________ is the net reproductive rate calculated from a static life table or age and fecundity table; ___________ is the highest per capita growth rate that a population can achieve and ___________ is the realized or actual per capita growth rate that a population does achieve.

Options: l lx r rm K dt xlxmx Ro

14. Thinking about competition between species, define the following

a ( = a12)________________________________________

B (= a21)________________________________________

Exploitation _______________________________________________________________________

15. Provide two separate, distinct advantages of asexual reproduction and one advantage of sexual reproduction.

Asexual ____________________________; ___________________________________

Sexual ____________________________

16. Limited resources, requiring the efforts of both parents, usually corresponds in a __________________ mating system. On the other hand with plentiful resources and reduced value of the male in rearing and protecting the young ______________________ or _________________________ may be favored.

17. Considering the increased likelihood of being spotted by predators or picking up a horrible disease while living in a large group, give three separate and distinct advantages of living in a large group that may confer a greater fitness upon those who do live in a large group.




18. What is the difference between a source population and a sink population and how might this distinction be of importance to conservation?

Difference(2 pts): Importance (1 pt):

19. In the following equation dN/dt = rmN(1 - N/K) define the following terms

dN _______________________ dt_________________________ rm___________________________

20. Graph the shape of the population growth curve for a population of starlings on an island that happens to follow the population growth defined by the equation in question 19 above. Graph Nstarlings with respect to time (t). Assume that K = 1,000,000 and that the initial population is 1000 and either a monotonic or damped oscilation approach to K.

21. Considering the logistic equation dN/dt = roN(1 - N/K), what is K and what could it mean in terms of real world populations like, for example, populations of bullfrogs living in the Lake Natomas?

(1 pt) K = _________________________ (name) What K means for bullfrog populations (2 pts):

22. On the following three sets of axes, starting with the initial populations indicated by the X draw the population trajectory showing how the relative numbers of each competitor changes with time and finally reaches an equilibrium value.

23. If a real population is stable and at equilibrium, what could cause it to fluctuate (Use the terms r and K in your answer)?

Essay Questions: Write a brief one-third-to one-half page essay on any two (2) of the following topics: (15 pts ea, 30 pts).

1. In studying the spatial distribution of nests in two different species of chipmunks living in two different parts of the Sierra Nevada, you observe that the distribution is evenly spaced in one species and completely random in another. What does this suggest to you about a) each species' social behavior and b) the resources available (plentiful or limiting) to each species.

2. Hamilton's rule has been used to explain how altruistic behavior can plausibly arise (from an evolutionary fitness perspective) in a social animal. Use a similar line of reasoning to explain how extremely selfish (or even spiteful) behavior is likely to be limited in social animals.

3. Humans are biological organisms that follow the same general rules of all other biological organisms. Explain the pattern of human population growth observed over the past several centuries. Which model for population growth does human population appear to follow and why has it not yet been limited by K?

4. Explain (briefly mentioning methods AND results) how Joseph Connell demonstrated that competition actually occurs between the barnacles Chthalamus and Balanus in the intertidal zones of Scotland. What did he find limiting the upward distribution of Chthalamus and the downward distribution of Balanus?

5. Explain how a life table works and how it is a valuable tool for biologists interested in predicting population dynamics of wild animals.