Which of the following statements about the response of arteriolar smooth muscle to changing oxygen partial pressures is true?
a. both systemic and pulmonary arterioles respond to a decrease in po₂ by constricting.
b. both systemic and pulmonary arterioles respond to a decrease in po₂ by dilating.
c. systemic arterioles respond to a decrease in po₂ by dilating, but pulmonary arterioles constrict in response to decreased po₂.
d. systemic arterioles respond to a decrease in po₂ by constricting, but pulmonary arterioles dilate in response to decreased po₂.
e. changes in po₂ do not affect arteriolar smooth muscle in the pulmonary system.

The organelle pictured is found in cells of and is theorized to have once been an independent organism.

Describe the change in phase and temperature as water moves from the oceans to the atmosphere and then returns to earth again as rain. a) evaporation : temperature increases; condensation : temperature decreases; precipitation (rain) : temperature decreases b) evaporation : temperature increases; condensation : temperature decreases; precipitation (rain) : temperature increases c) evaporation : temperature decreases; condensation : temperature decreases; precipitation (rain) : temperature decreases d) evaporation : temperature increases; condensation : temperature increases; precipitation (rain) : temperature decreases

How are fossils most commonly formed