Homeostasis my be defined as the mechanism of maintaining the proper life processes of the body. Almost all the living organisms has the tendency to perform homeostasis.
The main function of the homeostasis is to maintain the balance of the internal life in accordance with the change in the external and internal environment. The optimal level of the body is maintained by the process of the homeostasis.
I believe the correct answer is the first option. The term that would describe the tendency to maintain a balance or optimal level is called homeostasis. This common in biological systems. If this is not achieved most likely death of a cell would happen.
Population density is the average number of individuals in a population per unit of area or volume. For example, a population of 100 insects that live in an area of 100 square meters has a density of 1 insect per square meter.