A key role of the atrioventricular node is to
A. act as the pacemaker of the heart, by generating electrical signals in the right atrium.
B. slow down the conduction of the electrical impulse as it passes from the atria to the ventricles.
C. speed up the conduction of the electrical impulse as it passes from the atria to the ventricles.
D. block backflow of blood from the aorta into the right ventricle.
E. act as a barrier to prevent the electrical impulse in the atria from reaching the ventricles.
Answer: B
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In arthropods, locomotion is accomplished by muscles that work against
A. each other. B. the exoskeleton. C. a hydrostatic skeleton. D. mineralized bones. E. the pseudocoel.
Why do most viruses only infect one type of cell?
a. Viruses can only live in particular environments found within a select group of cells. b. Viruses can only find the necessary components to keep itself alive in one type of cell. c. Viruses can only infect cells that have the appropriate receptors for them to attach to. d. Viruses cannot move throughout the body so only infect the cells they first come into contact with.
The inheritance of sex-influenced traits can be dominant in one sex but recessive in the other
a. True b. False
Paleontological studies indicate that, over millions of years,
A. the extinction of species is not related to the community in which they lived. B. species that occurred together in the distant past still occur together today; the community has held constant. C. groups of species that have coevolved rise and go extinct together. D. species richness is constant over time. E. species seem to come and go individually as niches within a community become available.