Hi Amy and welcome to Salon Geek. I noticed that you have posted before recently with regard to assignment questions. Whilst we are more than happy to help you, we won't be doing you any favours by giving you the answers.
Have you tried to google this question?
Also, try to think this question through simply step by step. What is in our environment which could affect our epidermis eg. pollution, moisture, extremes of temperature etc....? Once you have these answers, think about how the epidermis is likely to behave when exposed to these environmental conditions.
The epidermis is our outer layer of skin. How does your skin behave with regard to external environmental factors?