Meaning of stimulus, Response and Irritability 

In order to survive in any environment, all living organisms need to be able to detect or percieve external and internal changes in their environment and respond or react appropriately to them. The ability to detect and respond to changes in the environment is called sensitivity or irritabilty.
A variation in conditions which can produce a change in activity of part or the whole organism is called stimulus while the change in activity by the organism is called response. Those part of the body which receive stimulus are known as the receptors while those parts that bring about responses known as effectors. Common external stimulus which bring about responses in organisms are temperature, light, PH, humidity, mineral salts.

Location: stend mandazi, Kakamega, Kenya