Imagine you are driving a car. What happens when you step on the gas pedal? What happens when you step on the brake? Your body and all living things are a lot like this car. Just as the car speeds up when you step on the gas and slows to a stop when you step on the brake, living organisms respond to changes in the environment in order to survive.

Source: Microsoft Clip Art Online

This process of responding to the environment and striving to reach a state of equilibrium, or constancy, is called homeostasis. The actions that trigger living things to respond are called feedback mechanisms.

Let's see how well your body responds to feedback. Play the reflex game.

How fast were you? So how was the message to "click" on the computer mouse delivered from your eyes to your finger? Let's take a look at some ways living organisms respond to their environment.