THERMOREGULATION BY

PRACHEE RAJPUT 4th SEM Zoology

Dept. Of Zoology And Applied Aquaculture Barkatullah University, Bhopal

SYNOPSIS

• INTRODUCTION • DEFINITION• TYPESa) Cold-blooded (Poikilothermic) animalsb) Warm-blooded (Homeothermic) animals• HIBERNATION• CONCLUSION• REFERENCES

INTRODUCTION

• Active life is limited to a narrow temperature range. Beyond this range many animals can survive in an inactive or torpid state. A large number of animals included all aquatic invertebrates have the same temperature as their surroundings. But birds and mammals generally maintain a nearly constant temperature in spite of wide variations in the surroundings temperature.

DEFINITION

• Thermoregulation is the maintenance of body temperature within a range that enable cells to function efficiently.

TYPES Poikilotherms (Cold-blooded):- Those animals in

which body temperature is varied with the environmental conditions are called Poikilotherms.

1. Aquatic Poikilotherms:- Thermoregulation in aquatic Poikilotherms is a simple phenomenon. Heat exchange in aquatic animals are largely by conduction and convection. Thermal environment of aquatic animals is relatively stable, Still seasonal variations do occurs in the surface layers of the sea and the lakes.

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2) Terrestrial Poikilotherms:-Terrestrial Poikilotherms maintain their body temperature almost equal to that of the environment. However terrestrial animals face greater temperature fluctuations. The heat balance of such animals is more related to their water balance as compared to the aquatic animals. In order to raise the body temperature the evaporation and heat loss by conduction are to be reduced and the heat gain by radiation and metabolic heat production are to be increased.

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Example, Lizards and other reptiles burrow at night when the desert or mountain temperatures are at their lowest. Some heat from the day remains underground and the reptiles body is prevented from freezing. At sun rise the lizard, which may have reached a body temperature as low as 5 degree during the night slowly emerges from its burrow to orient it self to the sunlight so that the maximum heat is obtained. By proper orientation lizards can attain body temperatures that are as much as 30 degree above that of the air.

Homeotherms:- Animals that maintain a fairly constant body temperature inspite of great variations of external temperature are said to be Homoeothermic animals.

TEMPERATURE REGULATION IN HOMEOTHERMIC ANIMALS

• For a body to maintain a constant temperature, the heat loss must be equal to heat loss.

o Heat loss :- it occurs by the following means. (a) Conduction:- Conduction of heat consists of direct transfer of the kinetic

energy of molecular motion and it always occurs from a region of higher temperature to one of the lower.

(b) Convection:- The transfer of heat in fluids is almost invariably accelerated by the process of convection which refers to mass movement of the fluid. The natural convection is caused by temperature difference.

(c) Radiation:- Heat transfer by radiation takes place in the absence of direct contact between objects. The intensity and the wavelength of this radiation depends upon the temperature of the radiating surface and its emissivity.

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(d) Evaporation:- The amount of heat required to achieve the phase change from liquid water to vapour is known as heat of vaporization. The heat of vaporization changes slightly with the temperature at which the evaporation takes place.

Heat gain:- The heat is gained by the following means. (1) From environment: The body can gain heat from the environment

through conduction, convection and radiation. (2) Heat production (Thermogenesis): The Du Bois temperature balance

shows that the following factors increase heat production.i. Active heat production is achieved through exercise and shivering.ii. Basal heat production depends on unconscious tensing of muscles,

disease and specific dynamic action of food.

HIBERNATION

Hibernation is a state of inactivity and metabolic depression in endotherms.

To cope with the limited food resources and low temperatures, some mammals hibernate in underground burrows. In order to remain in ‘stasis’ for long period, these animals must build up brown fat reserves and be capable of slowing all the body functions.

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• True hibernators (e.g., groundhogs) keep their body temperature down throughout their hibernation, while the core temperature of false hibernators(e.g., bears) varies with them sometimes emerging from their dens for brief periods. Some bats are true hibernators which rely upon a rapid, non-shivering thermogenesis of their brown fat deposit to bring them out of hibernation.

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