One definition of dry air is a theoretical sample of air that has no water vapor. ... Another definition of dry air is air that has a low relative humidity. When the relative humidity drops below about 40% the air feels dry to skin.
Why is the theory of evolution important? it disproves all other theories about how life began. it provides a topic for debate. it is a unifying concept in biology. it explains how life began. i know for sure, it is not "it is a unifying concept in biology."