气候适应

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人类对不同环境条件的遗传适应性。人体适应性,从对严寒、湿热、沙漠、高空以及疟疾流行环境的反应中表现出来。严寒地区适於身躯矮胖、四肢短小、面庞扁平而富於脂肪、鼻子狭窄而且体内脂肪层肥厚的人。这可使身躯以最小面积散发最低热量,四肢热量散发最少(能耐寒操作而防冻疮),防止冷空气自鼻腔进入肺部及颅底。适应湿热气候的人的特徵是︰身材高而瘦,以使体热辐射获有最大表面积,身体的脂肪少,因为不需在鼻道里温暖吸入的空气,鼻子大都宽阔,皮肤黑黝,可防止阳光辐射之害,也有助於降低流汗阈限。适应沙漠生活的人,能够大量流汗,但是必须应付由此引起的体内脱水的问题,因此这种人往往体瘦而不高,以使体内对水的需求量与损耗量都减低到最低限度。皮肤的色素沈着为中等程度,因为皮肤过黑固然利於防止阳光辐射,但也易吸热,这样就必须排汗散热,使水分有所损耗。夜寒适应性也是适应沙漠的人们的一种共同特点。高空适应性则要求人们对寒冷、低气压以及由之而来的氧气不足都能有所适应。一般说来,这种适应性必须靠增加肺组织的机能来获得。参阅acclimatization和race。

climatic adaptation, human

Genetic adaptation of human beings to different environmental conditions, such as extreme cold, humid heat, desert conditions, and high altitudes. Extreme cold favors short, round bodies with short arms and legs, flat faces with fat pads over the sinuses, narrow noses, and a heavy layer of body fat. These adaptations provide minimum surface area in relation to body mass for minimum heat loss, and protection of the lungs and base of the brain against cold air in the nasal passages. In conditions of humid heat, body heat must instead be dissipated; selection favors tall and thin bodies with maximum surface area for heat radiation. A wide nose prevents warming of the air in the nasal passages, and dark skin protects against harmful solar radiation. The desert-adapted person must compensate for water loss through sweating. A thin but not tall body minimizes both water needs and water loss; skin pigmentation is moderate, since extreme pigmentation is good protection from the sun but allows absorption of heat from direct sunlight, which must be lost by sweating. Adaptation to night cold, often part of a desert environment, provides increased metabolic activity to warm the body during sleep. High altitudes demand, in addition to cold adaptation, adaptation for low air pressure and the consequent low oxygen, usually by an increase in lung tissue. See also acclimatization, race.