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Stabilising selection 穩(wěn)定化選擇

Initially there is a wide range of fur length about the mean of 1.5cm.

最初，毛皮長度的范圍很廣，平均為1.5厘米。

Due to rapid breeding in either very cold or very warm weather, animals with extreme fur lengths survive.

由于在非常寒冷或非常溫暖的天氣中快速繁殖，具有極端毛發(fā)長度的動物得以生存。

When the temperature remains constant with little variation, the individuals with very short or very long hair become less numerous and are eventually eliminated from the population.

當溫度保持不變，變化不大時，毛發(fā)很短或很長的個體數(shù)量就會減少，并最終從種群中被淘汰。

Directional selection 方向性選擇

If the temperature falls, the individuals with longer fur length are at an advantage as they have better insulation against the cold.

如果氣溫下降，毛發(fā)較長的個體處于優(yōu)勢地位，因為它們有更好的絕緣性能來抵御寒冷。

There is a selection pressure favouring the animals with longer fur so these animals are more likely to survive and thus reproduce.

有一種有利于長毛的動物的選擇壓力，所以這些動物更有可能生存下來，從而進行繁殖。

Over several generations, the average fur length increases as more young have inherited the genes for long fur. When the mean fur length has reached the most advantageous length, the selection pressure ceases.

經(jīng)過幾代人的努力，平均毛皮長度增加，因為更多的年輕人繼承了長毛皮的基因。當平均毛皮長度達到最有利的長度時，選擇壓力就停止了。

Disruptive selection 破壞性選擇

If the temperature difference between summer and winter increases, long hair for animals being active during the winter or short hair for animals being active during the summer is advantageous.

如果夏季和冬季的溫差增大，在冬季活動的動物的長毛或在夏季活動的動物的短毛是有利的。

Intermediate fur length is disadvantageous. Therefore, two sub populations are formed over time.

中間的毛發(fā)長度是不利的。因此，隨著時間的推移，會形成兩個亞種群。

【微語】我在遙遠的家鄉(xiāng), 望著星空, 想象你在異鄉(xiāng)的生活, 心中滿是牽掛與祝福。