Q.92 Which one of the following examples represents an adaptation or a physiological activity that
DOES NOT minimize the loss of body temperature of animals?
(A) Feathers or fur
(B) Fat layers in the adipose tissue
(C) Shivering
(D) Vasodilation
Vasodilation does NOT minimize body temperature loss in animals. This physiological response increases blood flow to the skin, promoting heat dissipation rather than conservation.
Options Explained
Feathers or Fur (A)
Insulating feathers/fur trap air layers that reduce conductive/convective heat loss, minimizing temperature drop in endotherms like birds/mammals. Classic adaptation for heat retention.
Fat Layers in Adipose Tissue (B)
Subcutaneous blubber/insulating fat provides thermal barrier, significantly reducing heat conduction to environment (e.g., whales, polar mammals). Minimizes body temperature loss effectively.
Shivering (C)
Rapid muscle contractions generate metabolic heat via ATP hydrolysis, counteracting environmental cooling. Physiological thermogenesis that actively minimizes temperature loss.
Vasodilation (D)
Peripheral blood vessels dilate to increase skin blood flow, enhancing radiative/convective heat loss to cool overheated animals. Increases (does not minimize) body temperature loss.
Vasodilation increases rather than minimizes body temperature loss, distinguishing heat conservation from dissipation mechanisms in animal physiology.
Thermoregulation Mechanisms Comparison
Heat conservation (A,B,C) vs dissipation (D) reflects hypothalamic control: cold → vasoconstriction/shivering/erectile fur; heat → vasodilation/sweating/panting.
| Mechanism | Effect on Heat Loss | Hypothalamic Trigger |
|---|---|---|
| Feathers/Fur | Minimizes | Cold |
| Fat Layers | Minimizes | Cold |
| Shivering | Generates heat | Cold |
| Vasodilation | Increases | Heat |
Physiological Control Pathway
Hypothalamus detects core temperature deviation → activates effectors:
-
Cold: Sympathetic noradrenergic → piloerection, vasoconstriction, shivering.
-
Heat: Cholinergic sudomotor + inhibitory vasorelaxation.
Why Option (D) is Correct
Standard physiology confirms vasodilation as heat loss mechanism (opposite of conservation), making it the sole option that fails to minimize temperature loss.
