Why do people who exercise need more calories than people who don't exercise?

What is the relationship between absorbance of light and the rate of photosynthesis?

Hershey and chase confirmed that dna, not protein, was the genetic material. how do the results of their two experiments support this conclusion?

The human body needs energy in order to carry out life processes such as breathing. where does the body get this energy? a. from eating food b. from learning about new things c. from lying in the sun d. from sleeping