key words

• stimulus = change in the environment
• hormones = chemical messengers, carried by blood, control many bodily functions
• phototropism = plant growth response to light
• gravitropism = plant growth response to gravity
• homeostasis = maintaining a constant internal environment
• diabetes = a disease caused when your body cannot control your blood sugar levels
• negative feedback = a change from normal conditions in the body that causes a response which brings conditions back to normal