A limiting factor is a situation or condition that determines the speed or growth of a certain biological or social process, due to the fact that only a limited amount of it is available.
Therefore, a limiting factor is one that places a limit on the development of a certain characteristic within society. A clear example within biology is the lack of drinking water sources, which is a limiting factor for the development of population settlements, as occurs in the Sahara.
Thus, the existence of limiting factors puts a brake on the unrestricted development of human society, conditioning its development to the adaptation of individuals to the natural conditions of the environment.
Human society makes modifications to the environment to suit its needs. Humans can live in large numbers in harsh environments that do not necessarily support the population because of these modifications. Humans cannot, however, change the fact that they are affected by limiting factors. They can change the limiting factors in a specific area, but are still influenced by limiting factors in a larger area, either by region, or globally. Food, water, and energy supplies are limited and will only support a certain human population size. If the human population exceeds this size than disease, famine, and other limiting factors will naturally limit the population size.
The rat. I don't know if you meant zodiac ANIMAL or astrology sign like aquaris for example. however the rat zodiac animal is defined as the weakest of all the zodiac animals.