ANATOMY

Detailed explanation-1: -In physiology, a stimulus is a detectable change in the physical or chemical structure of an organism’s internal or external environment. The ability of an organism or organ to detect external stimuli, so that an appropriate reaction can be made, is called sensitivity (excitability).

Detailed explanation-2: -Pheromones. A pheromone is a secreted chemical signal used to trigger a response in another individual of the same species. Pheromones are especially common among social insects, such as ants and bees. Pheromones may attract the opposite sex, raise an alarm, mark a food trail, or trigger other, more complex behaviors.

Detailed explanation-3: -A stimulus is a change in the environment that produces a behavioral response. It may be an object or an event perceived through an animal’s senses. Stimuli may include the sight of food, the sound of a potential predator, or the smell of a mate.

Detailed explanation-4: -Stimulus: any change in an organism’s environment that causes the organism to react. It is a fancy way of saying “cause”. Example: An animal is cold so it moves into the sun.

Detailed explanation-5: -Final answer: The reaction to a stimulus is called response.