Animals in their Climatic Environment

Vocabulary flashcards covering animal thermoregulation, thermal neutral zones, heat exchange mechanisms, and neonatal vulnerability to thermal stress.

Endothermic

An organism that generates most of its body temperature internally through high metabolic rates rather than relying on the external environment.

Ectotherm

An animal that relies on the external environment, such as sunlight, to generate its body temperature.

Homeotherm

An animal that maintains a stable core body temperature within a narrow range by thermoregulation.

Poikilotherm

An animal whose core body temperature varies considerably with fluctuations in the external environment.

Thermoneutral Zone (TNZ)

The range of ambient temperature where no heat production or heat loss adjustments are required to maintain core body temperature within its normal value, requiring only adjustments in skin blood flow.

Lower Critical Temperature (LCT)

The ambient temperature threshold below which an animal leaves the thermoneutral zone and must actively expend energy to increase internal heat production.

Upper Critical Temperature (UCT)

The ambient temperature threshold above which an animal leaves the thermoneutral zone and must actively invoke physiological and behavioural mechanisms to cool its internal temperature.

Hypothermia

A pathological state occurring when the core body temperature decreases significantly below the normal physiological temperature range.

Hyperthermia

A pathological state occurring when the core body temperature increases significantly above the normal physiological temperature range.

Thermal Core

The vital internal region of the body consisting of the brain, thorax, and abdomen, which is defended to keep temperature stable.

Sensible Heat Loss

Heat dissipation via radiation, conduction, and convection that directly increases the temperature of the surrounding air.

Insensible (Latent) Heat Loss

Heat dissipation via the evaporation of water, which cools the body without increasing the temperature of the surrounding air.

Radiation

The physical process of heat transfer via electromagnetic waves between an animal's coat and its surroundings; darker coats absorb and radiate more heat.

Conduction

The direct transfer of heat between an animal's body and physical substrates it contacts; water conducts heat $25$ times faster than air.

Convection

The physical heat transfer mechanism occurring between an animal's body surface and moving fluid or air currents.

Evaporative Cooling

Heat loss achieved when liquid water transforms into vapor via sweating, panting, or wetting the body surface.

Relative Humidity

The percentage saturation of ambient air with water vapor, which directly influences and limits the rate of evaporative heat loss.

Countercurrent Heat Exchanger

A vascular adaptation in extremities where warm descending arterial blood runs close to cool ascending venous blood, pre-cooling arterial blood and returning heat to the body core.

Panting

A rapid, shallow respiratory mechanism utilizing a natural oscillation frequency to evaporate water from nasal turbinates for cooling without significant electrolyte loss or respiratory gas exchange.

Sweating

An active evaporative cooling process that results in the loss of both water and electrolytes ($Na^+$ and $Cl^-$) across the skin.

Wallowing

A behavioural heat dissipation strategy used by pigs (who have very limited sweating or panting ability) by coating skin in water or mud to facilitate evaporative cooling.

Brown Adipose Tissue (BAT)

Specialized thermogenic fat present in neonates such as lambs and calves (but absent in piglets) used to produce heat without shivering.

Non-Shivering Thermogenesis (NST)

Metabolic heat production generated by activating brown adipose tissue in cold-exposed neonates, accounting for up to $50\%$ of required heat.

Colostrum

A concentrated, easily digested food energy source consumed by neonates that increases basal metabolic rate by $50\%$ to protect against hypothermia.