In biology class 10, stimulus is defined as a detectable change in the internal or external environment that influences or causes a temporary increase of physiological activity or response in the whole organism or in any of its parts. Sensitivity is the ability of an organ or organism to detect external stimuli, so that an appropriate reaction can be produced. Sensory receptors receive information from outside the body, as in light receptors in the eye or touch receptors found in the skin, as well as from inside our body, as in mechanoreceptors and chemoreceptors. Examples of stimuli include changes in temperature, light, sound, pressure, and chemicals. The response to stimuli is a defining characteristic of life, and it is a way in which scientists can know if an organism has life in it or not.