A Level Biology Practice Exam

When engaging in exercise, the body’s metabolic demand for energy increases, and this, in turn, elevates oxygen uptake. Active muscles require more oxygen to produce the adenosine triphosphate (ATP) necessary for sustained physical activity. As exercise intensity rises, the cardiovascular and respiratory systems respond by increasing heart rate and breathing rate to enhance oxygen delivery to tissues while also improving the efficiency of oxygen utilization. This adaptation is crucial because it allows the body to meet the higher metabolic needs during physical exertion.

The other responses do not accurately reflect the physiology of exercise. The idea that exercise would decrease oxygen demand is incorrect, as physical activity inherently requires more oxygen. Claiming there is no effect on oxygen uptake ignores the fundamental physiological changes that occur during exercise. Additionally, exercise does not reduce the efficiency of oxygen transport; rather, it often enhances it through adaptations in the circulatory and respiratory systems, which improve oxygen delivery and uptake throughout the body.