Otto Loewi performed an experiment in which he first electrically stimulated the vagus nerve connected to a frog heart. He then passed the fluid bathing this heart to a second chamber containing a second frog heart not connected to a nerve. What did Loewi observe?
A. There was no effect on the beating of either heart.
B. The first heart showed an increase in beat rate, but there was no change in the second heart.
C. The first heart showed an increase in beat rate and so did the second heart.
D. The first heart showed a decrease in beat rate, but there was no change in the second heart.
E. The first heart showed a decrease in beat rate and so did the second heart.
E. The first heart showed a decrease in beat rate and so did the second heart.
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If an Arabidopsis plant does not express homeotic genes during flower development
A. The plant will die. B. The plant will only develop to the heart stage. C. The plant will not develop cotyledons. D. The plant will develop leaves instead of flowers. E. The plant will develop flowers instead of leaves.
The nitrogenous base found in DNA but not in RNA is
a. adenine. b. cytosine. c. guanine. d. uracil. e. thymine.
Sensory receptors are grouped into categories based on the
A) stimuli to which they respond. B) types of action potentials they generate. C) part of the central nervous system to which they connect. D) brain cells they stimulate.
The Strategic National Stockpile's points of distribution are:
A) facilities that are continuously manned and can deliver medications anywhere in the country within 72 hours. B) locations where patients with signs and symptoms of disease exposure are quarantined and provided treatment. C) preestablished facilities for the mass distribution of antibiotics, antidotes, vaccines, and other medications and supplies. D) medical treatment facilities that are regulated and activated by local, regional, or state governments in the event of a terrorist attack.