Metanephridia differ from protonephridia in all of the following ways except:
A. the urine produced in both systems is
more dilute than the body fluids.
B. metanephridia are surrounded by an
extensive capillary network, whereas
protonephridia are not.
C. selective reabsorption of materials occurs
via cells lining the tubules in protonephridia
and via capillaries in metanephridia.
D. fluid enters metanephridia through a funnel
-shaped opening.
E. fluid from the body cavity enters
protonephridia without first being filtered.
A
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Cnidarians evolved from an ancestral group of
(a) sponges. (b) protists. (c) fungi. (d) plants.
Most likely, immunology got its start in 1890 when these scientists discovered antibodies while developing a diphtheria antitoxin.
A) Edward Jenner and Louis Pasteur B) Elie Metchnikoff and Robert Koch C) Emil Behring and Kitasato Shibasaburo D) Jonas Salk and Albert Sabin
When experimentally applying alpha-bungarotoxin to a muscle, you find that it does not contract when the motor neuron leading to it is electrically stimulated. Knowing that this toxin blocks acetylcholine receptors, what can you conclude about the failure to contract?
A. A contraction fails to occur because an action potential is not generated in the muscle cell. B. A contraction fails to occur because this toxin prevents cross-bridge formation and thereby directly prevents contraction. C. A contraction fails to occur because this toxin directly prevents calcium ion release from intracellular stores. D. A contraction fails to occur because neurotransmitter release by the motor neuron is blocked at the neuromuscular junction. E. A contraction fails to occur because acetylcholine is not released from the motor neuron.
In the first step of glycolysis, glucose can be phosphorylated to glucose-6-phosphate, because
A) a phosphoanhydride bond has higher energy of hydrolysis than is required for formation of a phosphoester bond. B) transfer of a phosphate from ATP to glucose is endergonic. C) the reaction does not require an enzyme. D) the reaction is highly reversible. E) All of the above are correct.