The abiotic factors that influence population size and distribution are all the things in the environment that are not alive. Examples are the type of soil, fertile valley or rocky slope, etc. Density dependent factors are dependent on the number of individuals present in the population and include such things as parasitism, stress, predation and competition. Having large numbers of organisms in the population makes them more susceptible to parasites. Diseases are often caused by parasites and in this way help to check the population increase.
Stress is another factor that is related to large numbers of organisms.
Remember earlier when we talked about all those visitors who came to your house and how you felt. Some of those emotions were stress' related. In some populations birthrates decline when they are stressed or crowded into a confined space. Populations can also be limited by predation. As the population of prey species increases generally the number of predators will gradually increase also.