Dr. Reichler’s Bio 301M   MWF 9-10am    Print Name:_____________KEY_______________
Exam #2   March 27, 2006

    Read each question carefully and don’t hesitate to ask if a question seems unclear.  If possible, answer each question in the space provided, but if needed, continue on the back.  If you use a drawing as part of your answer, be sure to also include a written explanation. These questions have specific answers, although for some, more than one answer is possible.  To receive full credit you must clearly and fully answer the question being asked.  This exam is worth 103 points with the points for each question noted in parentheses.

1. Why is determining the time of the last common human ancestor important for differentiating between the “Out of Africa” and “Multi-Regional” hypotheses? (8 pts)
The “Out of Africa”hypothesis states that H. sapiens left Africa ~150,000 years ago and displaced all of the other hominids.  The “Multi-Regional” hypothesis states that H. erectus left Africa about 1,000,000 years ago and then evolved separately in different locations staying as a single species through interbreeding.  By determining the date of our last common ancestor one of these hypotheses can be eliminated.

2. Does relative testicle size tell us about the probability of male monogamy or female monogamy?  Why? (8 pts)
Large testicles relative to body size are developed in response to sperm competition.  If sperm are competing in the female reproductive tract, that indicates that females are not being monogamous.

3. Under what conditions is it beneficial for a male to have less offspring? (8 pts)
When resources are scarce, males may pass on more genes by spending time caring for fewer offspring.

4. Why do males sometimes have traits that are disadvantageous for their survival? (4 pts)
Female choice may dictate traits that males need to be able to reproduce.  Sometimes females choose traits that decrease the chance of male survivorship, and in that way the females can be certain that they are mating with high quality males.

5. In this figure from the article about pipefish:  What is the question being asked, and what is the answer? (8 pts)
Are their constraints on which sized females can mate in the sex role reversed pipefish?  Yes, only medium sized females can mate when their
is an excess of females.

6. What are one similarity and one difference between the two different types of self-incompatibility in plants? (8 pts)
Similarity:  (any one of)  Both recognize self.  Both inhibit pollen from reaching egg.
Difference:  (any one of)  One stops pollen on stigma, the other stops pollen tube growth through style.  One releases a goo, the other RNases.

7. If DNA was extracted from two H. floresiensis bones, and cut with the same restriction enzymes, but gave two different patterns of bands, what would you know about these bones?  Explain. (8 pts)
The bones are from two different individuals.  Restriction enzymes cut DNA at specific sequences, and if two different patterns are seen, then the DNA must have different sequences indicating DNA from two different individuals.

8. What do the tools found along with the H. floresiensis skeletons tell us about them, and why is this finding surprising? (8 pts)
The tools indicate a relatively high level of intelligence, and that is surprising due to their small brain size.

9. Neanderthals and humans coexisted for thousands of years.  What inference could be made if we discovered that Neanderthals went extinct soon after humans gained the ability to speak? (8 pts)
Language is one of the skills that scientists hypothesize allowed humans to form large groups.  Without this ability, Neanderthals may have been overrun by the large human groups.

10. Does the release of neurotransmitters always lead to the next neuron depolarizing? Why or why not? (4 pts)
No, inhibitory neurotransmitters can be released so that the next neurotransmitter will not depolarize.

11. If someone were in REM sleep and dreaming about running, would you expect neurons in the parts of the brain that signal leg movement to be active?  What about neurons in the legs?  Explain. (4 pts)
Brain- depolarized neurons.  During REM our minds often have similar activity to waking.  Legs- no signal.  Movement is inhibited during REM sleep.

12. How might the ability to dream confer an evolutionary advantage? (8 pts)
Dreaming may be a form of practice or rehearsal for threats or social interactions.  Individuals with the ability to dream would be better prepared to deal with these situations when encountered awake.

13. You see two of your friends arguing.  One wants to breed cats that behave super-friendly like dogs, and the other says that it cannot be done.  Who is correct, and why? (8 pts)
The breeding of friendly cats should be possible.  Many behavior have a genetic component such as the voles and monogamy or quantity of food eaten in humans.  By using artificial selection, friendly cats should be possible to produce.

14. Human males are typically about 1.2 times larger than females.  What can we infer about our ancestors if the males were 2 times larger than females? (8 pts)
Our male ancestors had more direct physical competition for access to reproduction with females.

Bonus:  In some species the female is larger than the male.  Why might this occur? (3 pts)
Since female resource input into reproduction is greater than males, they may be larger to support the amount of resources necessary to produce eggs and/or care for the offspring.