Asalt sample is placed into some water and nearly all of it dissolves without stirring or heating. the resulting solution is

The resulting solution is unsaturated.

An unsaturated solution is one in which the amount of solute can be increased. We know that the solution is unsaturated because there is no salt at the bottom of the solution and no means were required to increase the salt's solubility such as increasing temperature or stirring. Once the solution becomes saturated, additional salt will only deposit at the bottom unless changes in conditions are made. 

They carry out the exchange of gases as we breathe ( oxygen and carbon dioxide).