sensitivity – an organism's ability to react to stimuli or changes in the environment

To remember the meaning of sensitivity, use the following mnemonic:

The animal's senses were very sensitive (sensitivity), so it reacted to even the smallest changes in its environment. 

Sensitivity is the ability of living organisms to detect and respond to changes in their environment, known as stimuli. These stimuli can include light, temperature, sound, touch, chemicals, pH and water levels. In animals, sensitivity involves sense organs like eyes, ears, nose, tongue and skin that contain specialised receptor cells which detect stimuli and send signals through the nervous system to coordinate appropriate responses. 

Plants also show sensitivity by responding to stimuli such as growing towards light (phototropism), roots growing towards water and some plants, such as the Venus fly trap even respond to touch. 

This ability to sense and respond to environmental changes is crucial for survival as it allows organisms to find food, avoid danger and reproduce successfully.