In Computer Security, layers are a well-known practice that was taken from military techniques. The aim of this is to exhaust the attacker when he succeeds to penetrate the first layer of security by finding a hole, then he has to find a hole in the second layer and so on until he arrives at the destination if he succeeds.
This zone is highly important for life on Earth because it absorbs most of the ultraviolet radiation from the Sun; if this penetrated to the Earth’s surface it would act as a potent sterilizer, fatal for most forms of life
Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities.
