Question

prior to carrying out the investigation, the students learned that muscle cells use up $o_{2}$ in order to generate energy for movement, and produce $co_{2}$ as a byproduct.
based on the information in the tables, how did the students breathing and heart rates change in response to exercise?
choose 1 answer:
a the students breathing rates increased, but their heart rates decreased.
b the students heart rates increased, but their breathing rates decreased.
c the students breathing rates and heart rates both increased.
d the students breathing rates and heart rates both decreased.

Explanation:

When exercising, muscle cells need more energy. This requires more oxygen ($\ce{O2}$) and produces more carbon dioxide ($\ce{CO2}$). To supply more $\ce{O2}$ and remove more $\ce{CO2}$, the breathing rate increases. Also, the heart needs to pump more blood (which carries $\ce{O2}$ and removes $\ce{CO2}$) to the muscles, so the heart rate increases.

Answer:

C. The students’ breathing rates and heart rates both increased.