自然选择与人工选择
什么是自然选择？
人群中的个人具有很高的生殖潜力，并产生了大量后代。产生的数量大于该数量的生存。这被称为过度生产。人群中的个体在结构或形态，活动，功能或行为方面有所不同。这些差异称为变化。随机发生变化。有些变化是有利的，有些变化传递给了下一代，而另一些变化则没有。这些变体传递给了下一代，对下一代很有用。竞争竞争有限的资源，例如该物种内部或其他物种中的食物，栖息地，繁殖地和伴侣。有利变化的个人在竞争中具有更好的优势，并且比其他人更好地利用环境资源。 They survive in the environment. This is known as the survival of the fittest. They reproduce, and those who do not possess favourable variation mostly die before reproduction or do not reproduce. The number of individuals in a population does not change much because of this. Thus, favourable variations undergo natural selection and are retained in the environment. The natural selection occurs from generation to generation resulting in individuals better adapted to the environment. When this group of individuals of a population differs so much due to the gradual accumulation of favourable variations so that they cannot naturally interbreed with mother population, a new species arise.
什么是人工选择？
人类练习人工选择以驯化动物和植物。人工选择的基础是将天然种群隔离，并具有对人类有用的特征的有机体的选择性繁殖。可以实践这是为了增加肉类，牛奶产量等的数量。人在人工选择中施加方向选择压力。这可能会导致人群的基因型发生变化。人工选择可以通过近交和异育进行。近交涉及在密切相关的生物之间的选择性繁殖。这可以在同一父母的后代之间。这通常是由牲畜育种者进行的，以产生牛，猪，家禽和绵羊，并具有高产肉，牛奶，鸡蛋等。但是，近交可能会导致生育能力降低。随着纯合基因型开始占主导地位，强化繁殖可能导致遗传变异性降低。为了避免这个问题，繁殖者在近交几代人产生几代人后可能会切换到杂货。 Outbreeding is useful in plant breeding. It is now also being used to increase the commercial production of meat, eggs etc. It involves breeding between genetically distinct populations. Usually it is carried out between members of different strains and in some plants between closely related species. The progeny are called hybrids. The phenotypic characters expressed are superior to the parents. Recent advances in human knowledge on genetics have made it possible to eliminate or select certain characters in humans too.
人工选择和自然选择有什么区别？ •涉及的遗传机制中人工和自然选择之间没有差异。 •但是，区别在于，在人工选择中，进化过程受到人类的影响。 |
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