Evolution
Essay by Rositsa Staoykova
It was not until 4, 5 – 5 billion years that the forming of the Earth’s crust started. This is such an important fact for us because from then on the simplest organisms appeared. Due to the evolution more and more complicated organisms were formed, the most complicated of which is the human being. The question about how life on Earth started and evolved so that the human race could exist was interesting for many scientists such as Butlerov, Miller, Fox, Linei, Lamarck, and Darwin. This question is of present interest to many scientists even now in 2009.
Charles Darwin, born in England, collected and corrected some of the views of the other scientists before him, according to his own observations. In 1809 he was able to publish his work on the evolution of the organisms called ‘Origin of the species’. It was a whole, well-grounded theory, absolutely new for its time.
According to Darwin preconditions for the evolution are the variability and the heredity of the organisms. He explains the variability as the property of the organisms to acquire new marks or the process of the origin of the differences between the individuals of one and the same species. Darwin differentiates four types of variability: determined, undetermined, correlative and combinative. In the combinative variability we cross plants from different varieties or animals from different breeds. The parent marks are combined in different ways in the generation.
Darwin claims that the momentum of the evolution is natural selection. Natural selection is the process of preserving the useful marks for the species and the destruction of the useless marks. At first the giraffes’ legs and necks were of normal length. At one time there were many giraffes and little food for all of them, so the war for food between the species started. In this war only the giraffes with longer legs and necks were able to survive.
In Darwin’s work artificial selection is described as the process of selecting the organisms according to the qualities desired, by the person. So all of the dog breeds originate from the wild dog, all the pigeon breeds originate from the wild rock pigeon. Darwin describes the species like disparate variation and every variation he describes as a new species. The forming of the species is accomplished by divergence and convergence of the marks. The process of setting wide apart of the marks is called divergence. Convergence is the opposite process: forming of similar marks between the ungeneric individuals when they live in a place with similar conditions. As a result of divergence new variations are formed. Due to divergence the dolphin and the killer whale have appeared.
Although today with the help of advanced computer technologies we could see the shortcomings of Darwin’s theory, it was a masterpiece of its time and a huge step in the development of biology and genetics.
Essay by Rositsa Staoykova
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Последна модификация: Friday, 8 May 2009, 07:14 PM
