Which of these organisms is able to use several body surfaces, such as gills, skin, and lungs, for respiration?
A. amphibians
B. humans
C. birds
D. reptiles
E. None of these are correct.
Answer: A
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Most bacterial cells can keep from bursting in a hypotonic environment because of:
a. a stiff capsule. b. a rigid cell wall. c. a tough cell membrane. d. an efficient water pump. e. pumping large quantities of salts into the cell.
Following an F+ × F? mating, the donor is ________ and the recipient is ________.
A. F+; F? B. F+; F+ C. F?; F+ D. F?; F?
Poliovirus is an RNA virus of the picornavirus group, which uses its RNA as mRNA. At its end, the RNA genome has a viral protein (VPg) instead of a cap
This is followed by a nontranslated leader sequence, and then a single long protein-coding region (~7000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acid analogues. Short period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides. What conclusion is most consistent with the results of the radioactive labeling experiment? A) Host cell ribosomes only translate the viral code into short polypeptides. B) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones. C) The RNA is translated into short polypeptides, which are subsequently assembled into large ones. D) The large radioactive polypeptides are coded by the host, whereas the short ones are coded for by the virus.
Mobile prokaryotes can move around with the help of
A) endospores. B) flagella. C) sex pili. D) peptidoglycan. E) plasmids.