Stress responses are any responses that an organism makes or goes through, in response to a stressor that is causing a stress. A stress in accordance to Walter Cannon (1871-1945), is any disturbance that imbalances the internal environment of an organism also known as homeostasis. There are two major types of stressors that cause stress to animals: abiotic stressors and biotic stressors. Abiotic stressors are any ecological, geological, or climatological changes, that causes stress to the animal such as increased temperatures, and natural disasters. Biotic stressors are living things-related complications that causes stress; these include dominance, pollution, infection social pressures and competition.