A scientist wants to examine living cells lining the respiratory tract to determine how the cells use tiny hairs to move dirt and mucus away from the lungs. Which of the following instruments would be best, and why?
A) a light microscope, because it allows observations of whole, live cells
B) a transmission electron microscope, because it has high resolution
C) a scanning electron microscope, because it can reveal structures on cell surfaces
D) a scanning electron microscope, because it can be used to observe whole cells without slicing them
Answer: A
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A) prevents cell lysis. B) confers resistance to infection by viruses of the same type. C) confers resistance to infection by viruses of a different type (or strain). D) confers resistance to infection by many virus types and prevent cell lysis.
What caused the greatest mass extinction, in terms of species lost, at the end of the Permian?
a. global cooling b. sea level decline c. asteroid impact d. overhunting by humans e. increased volcanic activity
In autosomal dominant inheritance, ____
a. the trait often skips generations b. about one-fourth of the progeny in a pedigree will show the trait c. two affected individuals may have unaffected children d. males are more affected than females e. the aa phenotype will be affected
The organ(s) of the respiratory system that contain alveoli is (are) ________
A) bronchioles B) bronchi C) the glottis D) lungs