Homeostasis can be defined as the balance in which a system, animal, country, or planet maintains a variable around an ideal normal value, or set point. Homeostasis can refer to the human or animal body, eco-system, city, planet or even a solar system, in which each system must maintain a certain balance to function. For example, Earth maintains homeostasis through a range of variables such as the global temperature. If the global temperature raises to high (above the normal values) certain animals within its system will not be able to survive, where as if it goes to low (below the normal values) other animals will no longer be able to survive.
If you would like to learn more about homeostasis please view my homeostasis page.