1 An unopened container should last for 1-3 months at 40Â°F or less in the refrigerator, but some companies guarantee their product for up to 6 months.  If left in its partially-open original paper wrap, the exposed area of stick butter will begin to harden and smell stale after about a week, as oxygen sets in.
Quick Answer. Humans need a respiratory system because it is made up of organs that allow them to breathe. Breathing delivers oxygen to the body and takes away carbon dioxide. Every cell in the body needs oxygen to obtain energy from food. Continue Reading.
The respiratory system in humans, like most mammals, is centered around a set of lungs used for gas exchange. In humans, the lungs are connected to the oral and nasal cavities via the trachea to allow for transfer of oxygen to and carbon dioxide from the bronchial tree (figure 1.2) of the lungs.