26. Give an example of an inherent rhythm.

Menstruation, fiddler crab activity, mice activity are just a few examples of this kind of rhythm. Natural cycles which do not depend on external stimuli (temperature, daylight, rainfall,etc), but depend on the organism's own cycle are considered an "biological" rhythm.

Menstruation is often independent of outside factors unless there are other sexual mature women living with each other, then it appears that they will all sync their periods.

Fiddler crabs are active when the tide is out unpluging their burrows searching for food. If you move them to another area where the tidal rhythm is different they will still sync with the original tidal rhythm, even though they are swimming in water.

Mice have patterns of activity not associated with time of day. They maybe active for a few hours, scurrying about looking for food and then go into a sleep mode. They will wake up and repeat the pattern, and this goes on 24 hours a day.