When pollen from one species lands on the stigma of a flower from another species, the pollen tube typically ____
a. does not develop
b. forms, but the sperm cannot penetrate the egg
c. forms and grows to the ovary, but then stops
d. forms, but the sperm are killed
e. forms and the egg is usually fertilized, but the embryo rarely grows
ANSWER: a
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A liger is a result from a male lion and a female tiger. Male ligers are usually sterile. This is an example of
A. a prezygotic mechanism. B. hybrid inviability. C. hybrid sterility. D. hybrid breakdown. E. a prezygotic mechanism and hybrid sterility are correct.
A plant physiologist treats a leaf with abscisic acid and observes that the stomata close. What happened inside the guard cells during the experiment?
A. Abscisic acid influences the movement of sodium ions out of the guard cells. B. Abscisic acid influences the movement of potassium ions out of the guard cells. C. Abscisic acid binds carbon dioxide and causes carbonate crystals to block the stomatal opening. D. Abscisic acid binds with auxins and induces water molecules to exit the guard cells. E. Abscisic acid causes the guard cells to become more turgid.
The prospect of inhibiting myostatin and growing larger muscles may be tempting to a great many people. Is there any
danger to increasing muscle mass? Explain your answer. What will be an ideal response?
Hypoxia results in all of the following EXCEPT
a. hyperventilation. b. respiratory muscles working harder. c. heart muscles working harder. d. breathing difficulty. e. excessive oxygenation of the blood.