A plant population is found in an area that is becoming more arid. The average surface area of leaves has been decreasing over the generations. This trend is an example of __________.
a. stabilizing selection
b. disruptive selection
c. directional selection
d. gene flow
e. genetic drift
Answer: c. directional selection
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Antimicrobials that are macrolides
A. include azithromycin, clarithromcyin, and erythromycin. B. disrupt cell membrane function. C. are very narrow-spectrum drugs. D. include tetracyclines. E. are hepatotoxic.
Myasthenia gravis is an example of an autoimmune disease that involves
A. sensitized T cells. B. cytotoxic T cells. C. antibodies. D. IgD.
Two genes on each of four homologous chromosomes (HC) are described here, but only one of each
pair of sister chromatids is listed (HC1 and HC2). Capital and lower case indicate different alleles of the same gene. What four gametes will result from a single chiasma if the chromosomes have the following genes: HC1: ab; HC2: AB?
a. Ab, AB, ab, aB b. Ab, Ab, aB, aB c. Aa, Bb, ab, Ab. d. Ab, Ab, AB, AB e. AB, AB, ab, ab