Diurnal Fluctuation of Body Temperature

Which is true about the diurnal fluctuation of body temperature of animal-

Correct Answer: Body temperature is minimum in early morning & maximum in late afternoon (about 3 PM)

Body temperature follows a predictable circadian (diurnal) rhythm: minimum in early morning (~4–6 AM when metabolic rate and physical activity are lowest) and maximum in late afternoon (~3 PM).

Thermoregulation Center

• Center for thermoregulation AND osmoregulation: Hypothalamus
• Hypothalamus acts as a thermostat with a set-point temperature
• During fever: pyrogens (IL-1, TNF-α, PGE₂) reset the hypothalamic set-point upward → body temperature rises

Four Physical Heat Loss Mechanisms

• Radiation (heat waves from body to environment)
• Conduction (direct contact with cooler object)
• Convection (air/fluid movement carrying heat away)
• Evaporation (sweating + respiratory evaporation)

Animal-Specific Heat Loss

• True sweaters: Human, Horse, Camel
• True panters: Birds, Dog, Cat | Maximum panting: Birds
• Thermostability lowest: Camel | highest: Buffalo and Sheep