Question

ava conducted an experiment to determine respiratory rates during different activities. she counted the number of breaths per minute. ava noted that the number of breaths increases as physical activity increases. why is there an increase in the number of breaths per minute as activity increases?

○ as activity increases, breathing becomes more efficient.

○ as activity increases, the rate of the heart beating increases.

○ as activity increases, more oxygen is exhaled.

○ as activity increases, the oxygen needs of cells increase.

Explanation:

To determine the correct answer, we analyze each option:

• Option 1: Breathing efficiency isn't the main reason for increased breath rate during activity. The body needs more oxygen, not that breathing is more efficient.
• Option 2: Heart rate increase is a result of increased oxygen demand, not the cause of increased breath rate. The breath rate increases to supply oxygen, which then affects heart rate.
• Option 3: During activity, cells need more oxygen, so more oxygen is inhaled, and more carbon dioxide is exhaled, not more oxygen exhaled.
• Option 4: When physical activity increases, cells require more energy, which is produced via cellular respiration that needs oxygen. So the oxygen needs of cells increase, leading to more breaths to take in oxygen.

Answer:

D. As activity increases, the oxygen needs of cells increase.