Why do we break the body into “systems” when discussing it? why don’t we just talk about the entire body all at once

An obese man 5'5 and 200 pounds, seta a long-term goal to loose 50 pounds which of these is a resonable benchmark he might set for himself

Health and cardio respiratory fitness occurs when the heart is working, at minimum, 50 percent of heart rate reserve. true or false

Hiv is inactivated in the laboratory after a few minutes of sitting at room temperature, but the flu virus is still active after sitting for several hours. what are the practical consequences of these findings? a) hiv can be transmitted more easily from person to person than the flu virusb) the flu virus can be transmitted more easily from person to person than hivc) this property of hiv makes it more likely to be a pandemic than the flu virusd) disinfecting surfaces is more important to reduce the spread of hiv than the flu