Typhus fever, caused by Rickettsia prowazekii,is transmitted by
a) ticks.
b) human body lice
c) fleas.
d) mites.
Ans: b) human body lice
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Aristotle’s lantern is a tooth-bearing structure of the
(a) sea stars. (b) tunicates. (c) acorn worms. (d) sea urchins.
A temperature-sensitive (ts) mutation is often due to a ________ mutation that affects protein folding or activity.
A) null B) nonsense C) missense D) silent
When some birds mature, they migrate long distances to their breeding grounds or to escape harsh weather. A signal
for this type of behavior is often:a. a conditioned stimulus. b. day length. c. negative reinforcement. d. a sign stimulus. e. territoriality.
A cell contains a higher concentration of a substance than its surrounding environment. The cell membrane is highly permeable to this substance. What will happen as a result of diffusion?
A) The cell membrane will keep the substance inside the cell. B) The cell membrane will allow the substance to move to the cell's environment. C) The cell membrane will use the process of active transport to take in more of the substance. D) The cell membrane will allow more of the substance to enter the cell.