In the blood clotting process, platelets arrive at the site of damage and start secreting substances to attract more platelets. More platelets arrive at the site and secrete attractants to recruit more platelets. This is an example of:
A. negative feedback.
B. positive feedback.
C. feedforward regulation.
D. electrical signaling.
B. positive feedback.
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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.
The damage caused by ultraviolet radiation is
A) Repaired during transcription. B) Never repaired. C) Cut out and replaced. D) Repaired by DNA replication. E) Repaired during translation.
Enzymes used to cut DNA molecules in recombinant DNA research are ____
a. ligases b. restriction enzymes c. transcriptases d. DNA polymerases e. replicases
A(n) ________ is a category of the classification system of organisms that can include multiple kingdoms
Fill in the blank(s) with correct word