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.  

"i have always loved contemporary art and made it a general goal to work within the field. after a few nonprofit internships at museums and galleries, i decided to try the for-profit art world and was offered a job as the ad assistant at the magazine. i much prefer the pace of the for-profit art community and have stayed with the company for three years, with a promotion to an account manager last spring."

i just did this and got a 100.