The function of the thick outer coverings of insects and reptiles like rattlesnakes in desert biomes is to .

Shed

Explanation:

Snakes have to shed, or else their skin will become really crusty and flaky. Especially the ones that live in a desert. The sun destroys their skin, as it isn't as strong as ours.  

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.

gas and liquid