A  plant species arrives at  an  island  for the first time, where it  is  exposed to  a  new set of  pollinators.  Over the course of 20 generations, the characteristics of its flowers change. The figures above show the frequency distribution of petal length in the original colonizing population (Figure 1) and 20 generations later (Figure 2). Which of these explanations is consistent with the observed change in petal length?

#Question id: 11037

#Unit 7. System Physiology – Animal

A 22-year-old man has a muscle blood flow of 250 ml/min and a hematocrit of 50. He has a mean arterial pressure of 130 mm Hg, a muscle venous pressure of 5 mm Hg, and a heart rate of 80 beats/min. Which of the following is the approximate vascular resistance in the muscle of this man?

#Question id: 11036

#Unit 7. System Physiology – Animal

Under control conditions, flow through a blood vessel is 100 ml/min under a pressure gradient of 50 mm Hg. What would be the approximate flow through the vessel after increasing the vessel diameter to four times normal, assuming that the pressure gradient was maintained at 50 mm Hg?

#Question id: 11035

#Unit 7. System Physiology – Animal

A 72-year-old man had surgery to remove an abdominal tumor. Pathohistologic studies reveal that the tumor mass contains a large number of blood vessels. An increase in which of the following is the most likely stimulus for the growth of vessels in a solid tumor?

#Question id: 11034

#Unit 7. System Physiology – Animal

An increase in shear stress in a blood vessel results in which of the following changes?

#Question id: 11033

#Unit 7. System Physiology – Animal

The velocity of blood flow is the lowest in capillaries because ________.

#Question id: 11032

#Unit 7. System Physiology – Animal

An electrocardiogram (ECG) provides information about ________.