Wednesday, March 7, 2012

BAC Results for Second Midterm

The BAC met this afternoon to discuss questions from the second midterm. The BAC representatives came to talk to me about two questions.


A botanist discovers a new species of land plants with a dominant sporophyte, chlorophylls a and b, and cell walls made of cellulose. Which of the following structures, if present, would be least useful in assigning the plant to the correct group?
(a) endosperm
(b) seeds
(c) sperm that lack flagella
(d) flowers
(e) spores

The correct answer to this question was listed as (e). A land plant with a sporophyte dominant phenotype which means that it must be a fern, gymnosperm, or angiosperm. Endosperm would eliminate F and G, seeds would eliminate G and A, sperm that lacks flagella would eliminate F, flowers would eliminate A, whereas all three groups produce spores. Thus, (e) remains the sole correct answer.



A flask containing photosynthetic green algae and a control flask containing water with no algae are both placed under a bank of lights, which are set to cycle between 12 hours of light and 12 hours of dark. The dissolved oxygen concentrations in both flasks are monitored. Predict what the relative dissolved oxygen concentrations will be in the flask with algae compared to the control flask.
(a) the dissolved oxygen in the flask with algae will always be higher
(b) the dissolved oxygen in the flask with algae will always be lower
(c) the dissolved oxygen in the flask with algae will be higher in the light, but the same in the dark
(d) the dissolved oxygen in the flask with algae will be higher in the light, but lower in the dark
(e) the dissolved oxygen in the flask with algae will not be different from the control

This is a question from the textbook's test bank, so I don't know exactly what the question writer was thinking. When I read the question I thought "oxygen added by photosynthesis during the light and oxygen removed by cellular respiration both during the light and the dark. Thus, I agreed with the textbook's answer of (d).

However, several of you were thinking more deeply about the question than the question write and I were so you realized that it was not possible to determine the relative rate of oxygen production and use given the information provided. Thus, it was possible that answers (a), (c), or (d) were correct. Thus, this question will be omitted from the exam and everyone will receive credit for this question.

Thanks again to the members of the BAC and the BAC reps for the time and effort that they have put into the BAC so far this semester.

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