Identify and describe how an organism could respond to an external stimulus

Explanation: Homeostasis is the bodies way to maintain internal environment within normal range despite changing external environment. It achieves this by responding to stimulus using the brain or control centre. Receptors, chemoreceptors or thermoreceptors, in cells senses change in its environment, message is transmitted to the control centre via nerve impulse. Effectors such as organs and muscles receives the message and act accordingly by either enhancing the process as a results of positive feedback loop or inhibit the process from a negative feedback loop.

Receptors sense stimulus and transmit a message whereas effectors responds to message received by creating the necessary change needed to main everything withim exceptable range.

Another response to stimulus is when you touch a hot surface or stove. Thermoreceptors in your skin receives this and converts it to a nerve impulse that sends a message to the brain that you are getting burnt. The brain transmits that message to the muscles, the effector, causing you to remove your hand before you could even realise that you are getting burnt.