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 parts of the respiratory system work together to take in the oxygen we need to survive, and to get rid of carbon dioxide (waste gas). The circulatory system consists of the heart, blood vessels, and blood. Its purpose is to transport blood containing oxygen and nutrients throughout the body's tissues.