Darwin's theory of evolution, which answered many questions that Lamarck could not explain, was the most perfect theory of evolution at that time. This theory has made extremely important contributions in thought, academic content and scientific method. But it has also caused many controversies. First of all, Darwin's exposition on struggle for existence includes many aspects, namely, the struggle between biological and inorganic natural conditions; The struggle of the same species-intraspecific struggle; Struggle with different species-interspecific struggle. But he mainly refers to the intra-species struggle caused by overproduction. Obviously, Darwin's understanding is not comprehensive. In fact, among all kinds of creatures in nature, there are both conflicts and harmony; It includes both confrontation and cooperation. Darwin overemphasized the aspect of "struggle" and neglected the various connections in other aspects. Secondly, it is inappropriate for him to regard struggle for existence caused by overproduction as the main driving force of biological evolution. In fact, without overpopulation, species will mutate, old species will be extinct, and new and more developed species will take their place. Third, some of Darwin's views are still not supported by modern science. Darwin agreed that new traits acquired by organisms under the influence of environmental conditions can be passed down from generation to generation. Darwin's acquired genetic hypothesis (proposed by Lamarck), as a universal law in science, has not been fully proved so far.
Austrian geneticist Gregor Johann Mendel (1822 ~ 1884) put forward the theory of "genetic factors", that is, the genetic material controlling biological traits exists as a self-sufficient factor. They can hide, but they will not disappear. When meiosis forms gametes, the paired factors do not interfere with each other's separation; Through factor recombination. Mendel's point of view shows that it is factors, not environment, that determine genetic traits. This is obviously different from Darwin's view of acquired heredity. Dutch botanist De Frees (1848 ~1935) put forward the "mutation theory". He believes that evolution is not necessarily formed by tiny mutation (continuous mutation) as Darwin said. He said that mutation can be a discontinuity, which directly leads to the emergence of new species. Obviously, in Defrees' view, the role of natural selection in evolution is not important, but only plays a screening role in mutation. Thomas Hunt Morgan (1866 ~ 1946) is an American cytogeneticist. He put forward the "gene theory". He believes that genes are arranged in a straight line on chromosomes, thus establishing the corresponding relationship between different genes and traits. In this way, we can judge the change of traits according to the change of genes. Morgan believes that biological gene recombination must occur at a certain frequency, and its occurrence is not necessarily related to the external environment. It is believed that this mutation will stabilize in a new state once it occurs. Therefore, acquired traits are not hereditary.
Although the Neo-Darwinian School has put forward "germplasm theory", "gene theory" and "catastrophe theory", it has also caused a lot of controversy. First of all, neo-Darwinism studies biological evolution at the individual level, and evolution is a problem of group category. Therefore, this theory has certain limitations in explaining biological evolution as a whole. Secondly, most neo-Darwinian scholars ignore the important position of natural selection theory in evolution, so they can't correctly explain the process of evolution.
(1) population is the basic unit of biological evolution; The study of evolutionary mechanism belongs to the category of population genetics. (2) Mutation, selection and isolation are the three basic links of species formation and biological evolution. He believes that mutation is a common phenomenon, which can not only produce a large number of alleles, but also produce a large number of multiple alleles, thus greatly increasing the potential of biological variation. Once random mutation occurs, it will be influenced by selection. Through natural selection, harmful mutations will be eliminated and favorable gene mutations will be retained. As a result, the directional change of gene frequency leads to the formation of new biological gene types. After the genetic composition of a population changes, if this population can cross with other populations, it cannot form a stable species, that is, the formation of species must be achieved through isolation. This is his early comprehensive theory, also known as the "old comprehensive theory". 1970, Dubzhansky published another book, Genetics of Evolutionary Process. In this book, he also revised the above comprehensive theory. He believes that in most organisms, natural selection does not simply play the role of screening. In the state of heterozygosity, natural selection retains many harmful or even fatal genes because there are various selection mechanisms or models in nature. This thought became his "new synthesis theory" relative to the "old synthesis theory".
Fossil remains, relics and active remains of paleontology preserved in rock formations. The word fossil comes from the Latin word fossillis, which means digging. Fossil is the main research object of paleontology, which provides evidence for studying the life history of animals and plants in geological period. There have been records of fossils in ancient books in China, such as Ji Ran in the Spring and Autumn Period and Wu Jin in the Three Kingdoms Period, all of which mentioned the "keel" produced in Shaanxi, that is, the bones and teeth of ancient vertebrates; There is also a description of "stone fish" (that is, fish fossils) in Shan Hai Jing; There are descriptions of ancient insects in amber of Tao Hongjing during the Qi and Liang Dynasties in the Southern Dynasties. In Song Dynasty, Shen Kuo had a correct understanding of the origin of snail and mussel fossils and Wandu fish fossils. So far, the earliest bacterial fossils found are filamentous bacterial fossils from Walla Onna group in Australia 3.5 billion years ago.
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