A normal heart rate ranges between 60-100 beats per minute. The higher the heart rate is, the faster the blood is pumping through the heart. When exercising a persons heart will be higher because the brain and the muscles in the body are in need of oxygen so the heart needs to pump faster in order to sustain optimal performance.<span />
Paleontology is the study of the history of life on earth as based on fossils.
B. the contraction and relaxation of the brain
