I met with the BAC this afternoon to review the results of the retest exam. Three of the answers that I posted after class were incorrect (8, 12, 15) so those answers were changed to the correct answer prior to the BAC meeting (see the answer key below).
Also prior to the BAC I decided that answers d and e were equally good answers to this question so the question will be omitted from the exam and everyone will receive credit for this question.
After their meeting, the representatives of the BAC met with me to discuss the following two questions. Thanks again to the member of the BAC. I appreciate that they are willing to give up there time to make sure that the testing is as fair as possible.
Q. 23.
The question asks which of the following is always true. Because human populations do not always increase over time (e.g., the decline in global population during the plague) and females do not always prefer to mate with the male with the best genes (e.g., when they choose to mate with the male who gives the the largest food gift at the time of mating) those choices are excluded.
B - D = dN/dt and dN/dt = rN are mathematically true all of the time so answer c is always true making (c) the correct choice to this question. It appears that several students were confused and thinking that rN = dN/dt was only true for exponential growth. Remember, what defines exponential growth is that r is a constant.
Answer c remains the one, and only, correct answer.
Q. 28
This question examined the causes of food sharing in vampire bats. It appears that there was some confusion between this question and a question discussing food sharing that appeared on the 2010 exam.
Let's look at that question first.
2010 midterm
African Wild Dogs live in packs. Each day all individuals hunt solitarily for food. In the evening, they rejoin the pack and regurgitate some of the meat they caught that day so that it can be shared with other members of their pack.
5. Which of the following could explain food sharing in African Wild Dogs?
(a) females choose to mate with the male who gives them the most food
(b) females choose to mate with males who prove they are good at finding food
(c) kin selection
(d) reciprocal altruism
(e) c and d
Because all animals share and there is no mention of mate choice, answers a and b clearly don't apply. It is possible that food sharing behavior can be understood if groups were made up of related individuals. It is equally possible that the food sharing behavior is the result of reciprocal altruism. With no evidence presented in the question that allows you to separate between kin selection and reciprocal altruism, then the best answer is answer (e)
Q 28 Retest (The info about bats is all true by the way)
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 meal 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
First, I would rule out answer (c) cultural selection as a possibility because there is no discussion about how the "idea" for food sharing has spread.
"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. " The fact that individual who have helped others in the past are helped is consistent with the reciprocal altruism theory. However, the fact that they have never observed that a bat that hasn't been altruistic refused help when they needed it, is inconsistent with reciprocal altruism. Not so sure about the correctness of answer (b)
It says that most instances of sharing of has been observed among members of the same group and the groups members are related. This observation is consistent with the idea of kin selection so answer (a) is a possibility.
The question asks you to pick the best explanation for food sharing relationship. It is true that we do not know the final answer, but this is a common situation facing scientists. Given the observations they have they are forced to pick what they think is the most likely hypothesis before deciding on what study to do next. Faced with evidence that is consistent with the kin selection hypothesis yet some observations are inconsistent with the reciprocal altruism hypothesis, kin selection (a) is the best choice.
The answer remains (a) as the one correct answer.
For those of you who did not take the retest but would like to see what it was like, then here it is.
http://www.slideshare.net/MarkMcGinley/retest-2012
Multiple Choice Answer Key
1. c
2. c
3. b
4. a
5. b
6. a
7. e
8. b
9. c
10. d
11. b
12. a
13. a
14. e
15. e
16. a
17. d
18. e
19. c
20. e
21. b
22. omit- everyone receives credit
23. c
24. e
25. d
26. b
27. c
28. a
29. c
30. b
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