Which two systems work together to maintain correct levels of oxygen and carbon dioxide in the rat?

Well let's uhmmm how many bedrooms you want. if you want a garage. not to mention the price of the house?

It is evolution, because we all have some of the same traits like eye color or shape or ears.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.