1. What is the primary function of a biological clock?
A. Regulating hormonal secretion
B. Coordinating behavior with environmental changes
C. Maintaining blood pressure
D. Digesting food
Answer: B. Coordinating behavior with environmental changes
2. Which part of the brain acts as the master clock in humans?
A. Hippocampus
B. Pineal gland
C. Suprachiasmatic nucleus (SCN)
D. Amygdala
Answer: C. Suprachiasmatic nucleus (SCN)
3. Circadian rhythms typically follow a cycle of:
A. 6 hours
B. 12 hours
C. 24 hours
D. 36 hours
Answer: C. 24 hours
4. Which hormone is primarily responsible for regulating sleep-wake cycles?
A. Dopamine
B. Melatonin
C. Serotonin
D. Cortisol
Answer: B. Melatonin
5. Light signals to regulate circadian rhythms are received by which photoreceptors?
A. Rods and cones
B. Melanopsin-containing retinal ganglion cells
C. Bipolar cells
D. Optic nerve cells
Answer: B. Melanopsin-containing retinal ganglion cells
6. The term “zeitgeber” refers to:
A. A biological clock gene
B. An external cue that synchronizes circadian rhythms
C. A type of neurotransmitter
D. The sleep cycle
Answer: B. An external cue that synchronizes circadian rhythms
7. Jet lag occurs due to:
A. Hormonal imbalance
B. Disruption in circadian rhythms
C. Sleep deprivation
D. Physical fatigue
Answer: B. Disruption in circadian rhythms
8. What is the function of the CLOCK gene?
A. It regulates blood sugar levels.
B. It controls the molecular mechanisms of circadian rhythms.
C. It determines lifespan.
D. It activates immune responses.
Answer: B. It controls the molecular mechanisms of circadian rhythms.
9. Which of the following can disrupt circadian rhythms?
A. Regular exercise
B. Consistent sleep schedule
C. Exposure to artificial light at night
D. Proper nutrition
Answer: C. Exposure to artificial light at night
10. Which gland secretes melatonin?
A. Thyroid gland
B. Pituitary gland
C. Pineal gland
D. Adrenal gland
Answer: C. Pineal gland
11. Circadian rhythms are regulated by:
A. Genetic and environmental factors
B. Only genetic factors
C. Only environmental factors
D. Neural impulses
Answer: A. Genetic and environmental factors
12. Which of the following is a characteristic of circadian rhythms?
A. They are fixed and cannot be altered.
B. They reset based on light and dark cues.
C. They only regulate sleep patterns.
D. They are independent of any external factors.
Answer: B. They reset based on light and dark cues.
13. Which condition is associated with a disruption in circadian rhythms?
A. Asthma
B. Insomnia
C. Diabetes
D. Hypertension
Answer: B. Insomnia
14. Chronobiology is the study of:
A. Biological clocks and rhythms
B. Aging processes
C. Cellular structures
D. Genetic disorders
Answer: A. Biological clocks and rhythms
15. What is the period length of a circadian rhythm under constant conditions?
A. Exactly 24 hours
B. Slightly less than 24 hours
C. Slightly more than 24 hours
D. It varies widely
Answer: C. Slightly more than 24 hours
16. Which organism was first used to study circadian rhythms?
A. Fruit fly (Drosophila)
B. Mouse
C. Human
D. Frog
Answer: A. Fruit fly (Drosophila)
17. Peripheral clocks are found in:
A. Only the brain
B. All organs and tissues
C. Only the liver
D. Only muscles
Answer: B. All organs and tissues
18. The study of how time affects biological processes is called:
A. Cytology
B. Chronobiology
C. Ecology
D. Endocrinology
Answer: B. Chronobiology
19. What is the role of PER and TIM proteins in circadian rhythms?
A. They aid in digestion.
B. They form a feedback loop to regulate gene expression.
C. They enhance brain function.
D. They control blood pressure.
Answer: B. They form a feedback loop to regulate gene expression.
20. What is the primary signal for resetting the biological clock?
A. Temperature
B. Food intake
C. Light exposure
D. Physical activity
Answer: C. Light exposure
21. Which is NOT a feature of circadian rhythms?
A. Persistence in constant conditions
B. Entrainment by external cues
C. Fixed, unchangeable cycle duration
D. Temperature compensation
Answer: C. Fixed, unchangeable cycle duration
22. Seasonal Affective Disorder (SAD) is linked to:
A. Genetic mutations
B. Disruption in circadian rhythms
C. Viral infections
D. Nutritional deficiencies
Answer: B. Disruption in circadian rhythms
23. Which process in plants is influenced by circadian rhythms?
A. Photosynthesis
B. Respiration
C. Flowering time
D. All of the above
Answer: D. All of the above
24. Which environmental factor is most critical for entraining the circadian clock?
A. Humidity
B. Light-dark cycles
C. Sound
D. Wind patterns
Answer: B. Light-dark cycles
25. Which term describes rhythms shorter than 24 hours?
A. Ultradian rhythms
B. Circadian rhythms
C. Infradian rhythms
D. Seasonal rhythms
Answer: A. Ultradian rhythms
26. The feedback loop of circadian rhythms involves:
A. Positive and negative gene expression cycles
B. Only positive feedback
C. Only neural pathways
D. Only enzymatic reactions
Answer: A. Positive and negative gene expression cycles
27. Which protein acts as a light sensor in circadian regulation?
A. Opsin
B. Cryptochrome
C. Rhodopsin
D. Myosin
Answer: B. Cryptochrome
28. What role does the SCN play in the body?
A. Controls blood sugar levels
B. Synchronizes peripheral clocks
C. Regulates digestion
D. Enhances muscle strength
Answer: B. Synchronizes peripheral clocks
29. How does jet lag affect circadian rhythms?
A. Advances the clock
B. Delays the clock
C. Desynchronizes the clock
D. Has no effect
Answer: C. Desynchronizes the clock
30. Which of the following is an example of an infradian rhythm?
A. Sleep-wake cycle
B. Menstrual cycle
C. Heartbeat
D. Breathing
Answer: B. Menstrual cycle
These MCQs provide a comprehensive understanding of biological clocks and circadian rhythms, ideal for both academic and competitive exam preparation.
