背誦美文之植物擬態(tài)

　　Mimicry in Plants

　　Plant adaptations can be remarkably complex. Certain species of orchids, for instance, imitate female bees, other plants look and smell like dead animals, and still others have the appearance of stones. These strange adaptations to life represent just a few of the sophisticated means by which plants enhance their chances of survival. Mimicry in plants or animals is a three part system. There is a model: the animal, plant or substrate being initiated. There is a mimic: the organism that imitates the model. And there is a signal receiver or dupe: the animal that cannot effectively distinguish between the model and the mimic. Mimetic traits may include morphological structures, color patterns, behaviors or other attributes of the mimic that promote its resemblance to a model.That model may be either an unrelated species or an inanimate object, such as the background against which an organism spends most of its time. Mimicry is not an active strategy on the part of an individual plant; flowers do not deliberately trick or deceive animals into visiting them.Mimicry arises as the result of evolution through natural selection and the occurrence of random genetic mutations that lead over many generations to the appearance of favorable characteristics. If such traits help to camouflage a plant, for example, the plant is likely to have a survival advantage over other plants that are less well camouflaged.The plant will leave more descendants, thereby passing the advantage to the next generation. For natural selection to favor the evolution of mimicry, the mimicry must derive a reproductive advantage from modeling itself after another organism or object: its fitness, measured as the number of offspring produced that survive into the next generation, must be increased as the result of deception.

　　植物的適應性極為復雜。 某種蘭花模仿雌蜂，還有些植物看上去或嗅起來象死去的動物，更有些植物具有石頭的外表。 這些稀奇古怪的'適應性不過是植物的眾多求生手段中的一小部分罷了。 動植物的擬態(tài)包括三方面的內容：一是被模仿者，動物，植物或是生態(tài)基層，二是模仿者，即那些去模擬其它東西的生物，三是上當受騙者，即不能分辨模仿者與被模仿者的動物。 被模仿特征包括形態(tài)結構，色彩花紋，動作習性或其它模仿者實現(xiàn)它與被模仿者相似的特點。 被模仿者可以是其它種類的生物或非生命物，如棲居地的環(huán)境。 擬態(tài)并非某個植物主動的策略。 花朵并非故意誘騙動物來訪。 擬態(tài)是無數(shù)代自然選擇和遺傳變異的進化而獲得的有利特征的結果。 比如，有些特征有利于偽裝，那么具有這些特征的植物就比不具有的易于生存。 這種植物就會有更多的后代，并把這些特征代代相傳。 要讓自然選擇惠顧模仿者的進化，模仿者必須在模仿其它生物或物體中得到繁殖優(yōu)勢：它的適應能力，以存活至下一代的幼獸的數(shù)目來衡量，必定因為欺騙而加強了。

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