Where in an insect tracheal system does gas exchange occur between the air and a cell?
a. trachea
b. tracheal branches
c. gill filaments
d. tracheoles
e. spiracles
D
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Which of the following may be used by prokaryotes, under anaerobic conditions, as terminal electron acceptors?
A. nitrate B. nitrite C. sulfate D. carbon dioxide E. All of the choices are correct.
Squids are examples of
a. cephalopods. b. pseudopods. c. monopods. d. gastropods. e. polypods
India is in which demographic transitional stage?
a. birth and death rates equally high; growth rate low b. death rate dropping fast; birth rate declining but slowly c. birth rates declining and approaching the death rates d. birth rate falling below death rate; population size decreasing e. death rate greatly exceeds birth rate; population is close to extinction
Prokaryotes ____.
A. have a nucleus B. have complex, usually membrane-bound organelles C. always have cell walls D. are either bacteria or archaea E. always have flagella