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Biological Evolution

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Biological Evolution - Lesson Summary

According to Darwinian theory, natural selection is the most vital concept in evolution. Darwin’s studies showed that finches in the Galapagos Islands had survived by adapting to different habitats. He believed that the process of natural selection allows organisms to inherit traits from previous generations. These traits help them adapt themselves to their current environment and increase their chances of survival as they reproduce more successfully than others. Nature favours the survival of the fittest.
Darwin also put forth the concept of branching descent, which explained that various species have evolved from common ancestors by adapting themselves differently. However, this rate of change may have varied across species. In this way, Darwin refuted the old theory of evolution by the use and disuse of organs propounded by French naturalist Jean-Baptiste Lamarck. Around the time when Darwin proposed the theory of evolution, a British scholar and economist, Malthus’s thoughts impacted Darwin and he concluded that natural selection in population was also based on certain facts. Natural resources are limited the size of populations is generally stable. However, the population growth of organisms is limited because they compete with each other for natural resources. For example, a rise in the fish population of a river will lead to subsequent competition among them for resources. Therefore, organisms who adapt themselves and compete fiercely will survive while the weaker ones will perish.  Supporting his natural selection theory, Darwin pointed out that it was the inherited variations in organisms that helped them adapt to natural resources to the maximum and survive.  These organisms, who adapted themselves better to their environment, reproduced more. After millions of years, their progeny brought about a change in population characteristic and that’s how new forms of life came into existence. Although Gregor Johann Mendel, the founder of genetics, pointed out that inheritable factors influenced genotypes, Darwin chose to remain silent on this subject.  Hugo de Vries , believed that it was sudden mutations in populations that brought about evolution.  This idea went against the Darwinian concept of minor variations that occur slowly over many years and lead to evolution. In fact, de Vries argued that mutations were random and directionless. Mutation caused speciation and therefore it was alled saltation or a single-step large mutation.


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