Which factor, beginning in 1995, is responsible for the decline in chicken pox from a routine childhood disease to a rare infection?
A) ecological changes affecting the natural reservoir of the virus
B) routine vaccination
C) natural evolution of the virus to a less virulent form
D) development of effective anti-viral medications
E) changes in global migration patterns
Answer: B
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The life-cycle stages of the intestinal trematodes after the eggs are shed from the body via feces are best described as:
a. cercariae, miracidium larva, metacercariae, and redia. b. redia, metacercariae, cercariae, and mira-cidium larva. c. miracidium larva, redia, cercariae, and metacercariae. d. metacercariae, miracidium larva, cercariae, and redia.
Assuming a single cross-over event, the completion of meiosis produces ____
a. three daughter cells with parental chromosomes and one daughter cell with a recombinant chromosome b. four daughter cells with recombinant chromosomes c. two daughter cells with parental chromosomes and two daughter cells with recombinant chromosomes d. one daughter cell with parental chromosomes and one cell with recombinant chromosomes e. two daughter cells, each with recombinant chromosomes
In which of the following organisms would one expect to find flame cells?
a. grasshoppers b. rabbits c. planaria d. sea anemone
Deciduous trees drop their leaves in response to
A. cold weather. B. the length of day. C. how long they have been growing. D. None of the above is true.