Drug-resistant populations of microbes arise when
A. exposure to drugs selectively kills sensitive cells, allowing overgrowth of resistant cells.
B. exposure to drugs causes mutations that produce resistance.
C. resistant cells become numerous in a population due to their greater vigor.
D. the patient becomes immune to the drug.
E. synergy between medications occurs.
Answer: A
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A) CD3. B) CD28. C) Ig?. D) Ig?.
Double fertilization occurs when
A. the sperm and tube nuclei fertilize the egg. B. two sperm cells fertilize the two polar nuclei. C. one sperm fuses with the egg and the other sperm fuses with both polar nuclei. D. the polar nuclei fuse with the egg after it has fused with the sperm.
A mollusk that has arms connecting directly to the head of the animal is a
A. gastropod. B. cephalopod. C. bivalve. D. fluke. E. chiton.
There is a homeostatic or regulatory mechanism that turns appetite and metabolism high or low to maintain the "fat set point." This mechanism is influenced by which of the following?
A) the aroma of food cooking stimulating salivation B) the amount of time since your last meal C) a hormone called leptin D) using more calories than you eat