Plants have a which prevents bursting in a hypotonic environment

The answer is cell wall. It is the rigid outer layer of plant cells that is composed of subunits of cellulose molecules, pectin,  lignin, or hemicellulose. It enables the plant to withstand turgor pressure, without bursting, required to give them support.

The relationship between a sloth and the moss that grows on the sloth's hair

Explanation:

The sloth benefits because it's able to camouflage and blend in with it's environment more with the presence of the moss, and the moss benefits because it has a place to grow and live; therefore it's a mutualistic relationship.