Question

Sinking of zooplankton during the day and rising to the surface at night is an example of

• A. circinal rhythm
• B. circadian rhythm
• C. tidal rhythm
• D. None of these

Answer 1

Answer: (B)

circadian rhythm

Answer 2

Circadian rhythm or diurnal rhythm is any $24$ hour periodicity in the behaviour or physiology of animals or plants. Examples are the sleep/activity cycle in many animals and the growth movements of plants. Circadian rhythms are generally controlled by biological clocks.