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Maintaining a high constant body temperature in mammals has both positives and negatives. What are they?

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Samantha Foster Biology - Rhetoric * Maintaining a high constant body temperature in mammals has both positives and negatives. What are they? * Describe how a mammal may respond to cold temperatures both in the short and long term. * How would the response of a reptile such as a chameleon differ from that of a mammal when exposed to low temperatures? Endothermic organisms maintain a stable core body temperature through their own adapted physiological mechanisms and appropriate changes in its behavioural patterns. The ability of an endotherm to keep its internal environment at a constant temperature allows the enzymes catalysing the vital biochemical reactions to be close to their optimum temperature, giving an efficient metabolic rate. The metabolic rate is defined as the rate at which all the cells in the body carry out their biochemical reactions. This constant high metabolic rate allows the endotherm to produce rapid movement in colder regions. For example the ability for the body to respire quickly when faced with the fight or flee situation, under the influence of the hormone adrenaline. ...read more.


triggers the autonomic nervous system, which brings bout the physiological responses to the cooler temperature: * Vasoconstriction of the arterioles supplying the skin with blood. These vessels narrow reducing the blood flow to the surface capillaries by redirecting the majority of blood through a shunt vessel. Thus the amount of heat lost to the surroundings by radiation and conduction is greatly reduced. * Piloerection involves the erector pili muscles contracting, and thus pulling on the hair follicle causing it to raise on the body of the mammal. This is a reflex action more commonly used in animals with dense fur. The piloerection makes the fur "thicker" and as a result more air is trapped, reducing heat loss by convection. * Shivering is the rapid contraction and relaxation of the muscles of the body, causing the muscular tissue to respire and release more heat, as respiring muscles release approximately 4 to5 times more heat than those at rest. The thyroid gland also secretes adrenaline further increasing the metabolic rate and as a direct result, heat production is also escalated. ...read more.


The chameleon however is a-typical when considering other lizards as it can change the colour of its skin. Thus the lizard can make its skin colour darker, to absorb more heat from the surroundings. In some tropical countries the temperature near the ground may reach as cold as 0oC, at this temperature the biochemical reactions occurring in the body of the lizard would be so slow it would run the risk of dying. As a result the lizard must find a warmer location so spend the night, usually it has a burrow it can retreat to when it gets too cold. The burrow will usually remain at a constant temperature of approximately 20oC; conditions the lizard will be able to survive. Lizards will also adjust their body position so when heat needs to be absorbed from the surroundings it is done in the most efficient way, by placing themselves at right angles to the direction of the rays. Despite these behavioural adaptations most endotherms are ill suited to living in colder climates, as there is insufficient energy available to maintain a suitably high metabolic rate. ...read more.

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