Final answer:
The tympanic membrane is involved in hearing and vibrates in response to sound, while the nictitating membrane is a protective third eyelid found in certain animals.
Step-by-step explanation:
The difference between a tympanic membrane and a nictitating membrane lies in their structure and function. The tympanic membrane, also known as the eardrum, is a thin diaphragm that separates the outer ear from the middle ear. It vibrates when struck by sound waves and is crucial in the hearing process. On the other hand, a nictitating membrane, often found in animals such as birds and some reptiles, is a protective third eyelid that can move across the eye to protect and moisten it while maintaining visibility.