Chapter 31, Problem 26A

Summary Introduction

Introduction: Circadian rhythm is a cycle that occurs daily. Animals, even humans repeat behaviors in a rhythmic cycle.

Answer to Problem 26A

Correct answer:

The correct answer is option (b) Sleep/wake cycle.

Explanation of Solution

Explanation/justification for the correct answer:

Option (b) Sleep/wake cycle.

The daily cycle of sleeping and waking is influenced by external factors in animals. But, most animals that include humans too have developed an internal clock, known as a biological clock which helps in maintaining the daily rhythm of the sleep/wake cycle of 24 hours.

Explanation for incorrect answer:

Option (a) migration

The behavior in some animals due to which they move to some other place basically to long distances seasonal to new locations is migration behavior or migratory behavior. This is a seasonal cycle.

Option (c) hibernation.

It is the state of deep sleep of an animal through which it saves energy and survives the winter without eating much. The body temperature decreases and heartbeat and breathing also slow down. As a result, energy is stored. This is a seasonal cycle.

Option (d) reproductive cycle

The cycle during which an animal is in the most fertile stage to reproduce and give birth to an offspring is known as the reproductive cycle. The time and duration of the reproductive cycle vary from animal to animal. It occurs monthly in some whereas in some animals it occurs once in six months.

Conclusion

Hence, option (b) Sleep/wake cycle is an example of a circadian rhythm.