Okay so northern Africa and the Sahara desert is the best example of desertification. 
2 ways humans have contributed to that is: 1) pastoral nomadism 2) little to no settlements to increase water supply 
how it impacted the environment: so now the environment there is sandy, only organisms adapted for those extreme environment can live there ex. camel, cactus, etc., 
how it impacted quality of life: quality of life diminished, not enough water to sufficiently feed the populations, people live in extreme poverty, people are moving away, and the climate is very dry and hot, pretty much not a place anyone would want to live
http://eden-foundation.org/project/desertif.html
https://www.sciencedaily.com/releases/2017/03/170314111320.htm
        
             
        
        
        
The skin acts as a barrier for protecting the body from the harmful things such as sun rays, moisture, cold.
<u>Explanation:</u>
Skin plays an important role in regulating body temperature. It helps to prevent harmful substances enter into our body, and does not allow to loss water in our body. Its form the barrier that prevents harmful substances and microorganisms enter in our body. 
Our skin is the protecting layers and against loss of water and blood from our body. Its help us to maintain the constant body  temperature. The important role of the skin us to protect our body from the ultraviolet rays. 
 
        
             
        
        
        
C is not an example of evolution so that is your answer
        
                    
             
        
        
        
The correct answer is neutrons, they do not carry an electronic charge.
Hope this helps.
        
             
        
        
        
Answer: by using artificial light (grow light) in place of sunlight
Explanation: Plants generally needs sunlight to grow and survive through a process known as photosynthesis, this is when Plants and other organism uses sunlight to convert water, carbon dioxide and minerals into energy rich compound (starch) while oxygen is been released into the environment.
However in the absence of sunlight, artificial light know as grow light can be used, these lights are design in such a way that it emits lights of wavelengths that are appropriate for photosynthesis. The grow light replaces the sun as a source of photons in the process of photosynthesis.