Questions about evolution ~ ~ ~

"Natural selection, survival of the fittest."

"Survival of the fittest, elimination of the unfit."

These are two core sentences of evolution.

Evolution was used in biology after19th century, especially the change and development of biology from simple to complex and from low to high. Also known as evolution. The word evolution comes from the Latin evolutio, which means to unwind or unwind tightly wound paper rolls.

[Edit this paragraph] History

Darwin traced the development of the thought of biological change and the view of nature about the mutual transformation and evolution of all things back to the early stage of human civilization. For example, China's Yin-Yang Eight Diagrams Theory in the Book of Changes simplifies nature into eight basic phenomena, namely, heaven, earth, thunder, wind, water, fire, mountains and rivers, and tries to explain the complex changing laws of the material world with Yin-Yang Eight Diagrams. Anaximander, an ancient Greek (about 6th century BC), believed that life was originally produced by mud in the sea, and primitive aquatic creatures were transformed into terrestrial creatures through metamorphosis (similar to the molting of insect larvae). In the Western Middle Ages, the Christian Bible described everything in the world as a special creation of God. This is called creationism. Teleology, which is accompanied by creationism, holds that the arrangement of nature has a purpose. "Cats are created to eat mice, mice are created to eat cats, and the whole nature is created to prove the wisdom of the creator."

From the Renaissance in the second half of the15th century to the18th century, modern natural science was formed and developed. The dominant view of the scientific community in this period is invariance. At that time, this view was expressed by I Newton and C·V· Linnaeus as a scientific law: the earth moves because of the so-called first driving force, and then moves forever. Biological species were like this before, now and in the future. /kloc-in the second half of the 0/8th century, my Kant's celestial theory first opened the first gap in the unchanging view of nature; Subsequently, the natural view of transformation theory gradually formed in various fields of natural science. Some biologists in this period were often confused between the two concepts. For example, in his later years, Linnaeus deleted the word species invariance in his book Natural Systems. French biologist G.-L.de Buffon introduced transformation theory into biology, but he lingered between transformation theory and invariance theory all his life. J.-B.de Lamarck expounded his views on biotransformation in the book Animal Philosophy published in 1809, and never wavered.

From the end of 18 to the end of 19, most zoologists did not seriously study biological evolution, deviated from the traditional materialism of ancient Greece and fell into idealism. Although the "vitality theory" admits that biological species can be transformed, it attributes the cause of evolution to immaterial internal forces, and holds that the "internal forces" of organisms, that is, vitality, drive the evolution of organisms, making them more and more complex and perfect. However, the theory of vitality lacks practical evidence and is an idealistic speculation. The most famous vitalist is the French biologist Lamarck. /kloc-the ultimate teleology or direct birth theory, which appeared in the late 0/9th century, holds that no matter how the external environment changes, biological evolution has an established route and direction.

Later generations called Lamarckian's viewpoint of biological evolution Lamarckianism or Lamarckianism. Its main points are as follows:

(1) Species are variable, and species are groups of mutated individuals.

(2) There are a series of grades (steps) from simple to complex among creatures in nature, and creatures themselves have an inherent "willpower" to drive them to develop and change from low to high.

③ Organisms have strong adaptability to the environment; Environmental changes will cause biological changes, thus improving its adaptability; The diversification of environment is the fundamental reason of biodiversity.

(4) The change of environment will cause the change of animal habits, which will make some organs develop when they are used frequently, while others will degenerate when they are not used; Directional variation under the influence of environment, that is, acquired traits, can be inherited. If the environment changes in a certain direction, due to the use of organs and acquired inheritance, tiny variations gradually accumulate and eventually organisms evolve.

The inner will in Lamarckian theory is idealistic; Acquired is mostly phenotypic variation, and modern genetics has proved that it cannot be inherited.

Darwin's theory

On July 1858, C.R. Darwin and A.R. Wallace read a paper on the origin of species in linnean society of london. Later generations called their theory of natural selection Darwin-Wallace theory. Darwin systematically expounded his theory of evolution in the book Origin of Species published in 1859. The main idea of its core principle of natural selection is that all living things tend to over-breed, and living space and food are limited, so living things must "fight for survival". Individuals in the same population have variation, those individuals who have favorable variation and can adapt to the environment will survive and reproduce, and those individuals who have no favorable variation will be eliminated. If the change of natural conditions is directional, then in the historical process, after long-term natural selection, small variations will accumulate and become significant variations. This may lead to the formation of subspecies and new species.

Darwin's theory of evolution holds that biological variation, heredity and natural selection can lead to adaptive changes of organisms from the perspective of the interaction between organisms and the environment. Because it is based on sufficient scientific facts and can stand the test of time, it has had a far-reaching influence in academic circles for more than one hundred years. But Darwin's theory of evolution still has some obvious weaknesses:

(1) His principle of natural selection was based on the popular hypothesis of "fusion inheritance" at that time. According to the concept of fusion inheritance, the genetic material of father and mother can be fused like blood; In this way, any new mutation will disappear after several generations of integration. How do mutations accumulate and how does natural selection work? ? (2) Darwin overemphasized the gradual change of biological evolution; He believes that "there is no jumping in nature" and explains the jumping evolution shown by paleontological data with "extinction of intermediate types" and "incomplete fossil records". In recent years, his views have been increasingly criticized by discontinuous equilibrium theorists and neo-capitalist theorists.

The development of evolution after Darwin

1865, Austrian botanist G.J. Mendel got the correct conclusion of particle inheritance from pea hybridization experiment. He proved that genetic material can be separated and recombined in the process of reproduction and passage. With the establishment of genetics in the early 20th century, T.H. Morgan and others further established the theory of chromosome inheritance, which fully revealed the basic laws of inheritance. This should make up for the defects of Darwin's theory and contribute to the development of evolution; But at that time, most geneticists (including Morgan) opposed Darwin's theory of natural selection. There has been a serious crisis in people's belief in Darwin's theory of evolution.

(1) Neo-Lamarckianism and Neo-Darwinism.

From the end of 19 to the beginning of the 20th century, some new evolutionary theories appeared. At the beginning of the 20th century, Dutch botanist H. de Fries put forward the mutation theory of "species are produced by mutation" according to the variation of evening primrose, and opposed the gradual change theory. This theory was supported by many geneticists at that time. Although some followers of Lamarckian theory abandoned Lamarckian concept of inner will, they still emphasized acquired inheritance, which was regarded as the main factor of evolution. Michurin's theory, promoted by T.D. lysenko in the Soviet Union in 1950s, emphasized that organisms can undergo directional mutation under the direct influence of the environment, and acquired nature can be inherited. All these views are called neo-Lamarconism. 1883, A.F.L weismann proved the error of acquired heredity by experiments, emphasizing that natural selection is the driving force of biological evolution, and his view was later called neo-Darwinism.

② Modern comprehensive evolution theory.

In the 1920s and 1930s, firstly, R.A. Fisher, S.Wright and J.B. Shadane combined biostatistics with Mendel's theory of particle genetics, reinterpreted Darwin's theory of natural selection and formed population genetics. Later, C.C. Chet Vyrikov, T.dobrzanski, J.Huxley, E.Meyer, F.J. Ayala, G.L. stebbins, G.G. Simpson and J.W. Valentine developed Darwin's theory and established modern comprehensive evolution based on chromosome genetics, population genetics, species concept, paleontology and molecular biology. Modern comprehensive evolutionary theory completely denies the inheritance of acquired traits, emphasizes gradual evolution, thinks that evolution is a phenomenon of groups rather than individuals, reiterates the overriding importance of natural selection, and inherits and develops Darwin's evolutionary theory.

③ Neutral theory and discontinuous equilibrium theory.

From 65438 to 0968, Japanese scholar Gen Kimura proposed the neutral theory of molecular evolution based on the materials of molecular biology. It is believed that at the molecular level, most evolutionary changes and variations within species are not caused by natural selection, but by the random drift of neutral or nearly neutral mutant alleles, which is contrary to the universal view of natural selection in modern comprehensive evolution (see the neutral theory of molecular evolution). 1972, N. Eldredge and S. J. Gould * * * both put forward the "punctuated equilibrium" evolutionary model to explain the obvious discontinuity and jump in the evolution of paleontology, and thought that the gradual evolutionary model based on natural selection, that is, the linear gradual evolutionary model, could not explain the origin of more than one taxon, and opposed the only progressive evolutionary view of modern Darwinism. The argument is still going on (see break)

Social Darwinism: Some people think that the ruthless competition for survival in nature should be introduced into people's social life. They believe that pure competition can promote human progress, and competition between individuals and countries (including the ultimate war of destruction) should be advocated, so as to eliminate losers and some people who are "unfit for survival". Thereby purifying human genes and optimizing human race. It is the embodiment of an extreme thought. It is to deny the basic concept of human sociality, but only to agree that "people come from animals" and deny the basic attribute that people are above animals.

[Edit this paragraph] Small evolution and big evolution

American geneticist R.B. Goldschmidt believes that ordinary natural selection can only act on genes within the range of species, resulting in small evolutionary changes, that is, small evolution; The evolutionary step from one species to another requires another way of evolution, that is, great evolution. He believes that great evolution is achieved through his hypothesis of systematic mutation (gene mutation involving the whole genome). In this way, a new species, even a new genus or family, can be produced immediately. Simpson, an American paleontologist, agrees that the study of evolution can be divided into two major areas: the small evolution of evolution below species and the great evolution of evolution above species, but he disagrees with Goethe. He doesn't think that small evolution and big evolution are different or unrelated ways of evolution.

Small evolution studies the evolutionary changes below species, including: ① the factors and mechanisms of small evolution, and studies how genetic mutation, natural selection, random phenomena (such as genetic drift) and other factors cause the changes of population genetic composition. (2) speciation, that is, to study the formation mode and process of new species, how tiny evolutionary factors lead to the formation and development of isolation among the same species, and to study the intra-species differentiation and the development process from subspecies, semi-species to complete species.

Macroevolution studies the evolutionary changes of taxonomic units of more than one species on the geological time scale. The main object is fossils, and the smallest research unit is species. The main research contents include: ① the origin and evolution factors of more than one taxon. (2) Evolution mode, the change and formation of evolution line system in time dimension. (3) the speed of evolution, the speed of morphological change, the speed of emergence or extinction of taxon, the life span of species, etc. ④ Direction and trend of evolution. ⑤ The law and reason of extinction and its relationship with evolution trend and speed. Small evolution and big evolution are interlinked at the level of species. In fact, both small evolution and big evolution study speciation. In recent years, there has been a heated debate in academic circles about the relationship between small evolution and big evolution. Punctuated equilibrium school thinks that the fact of great evolution cannot be explained by the mechanism of small evolution; However, modern comprehensive evolution theory holds that small evolution is the basis of big evolution, and the mechanism of small evolution can explain the phenomenon of big evolution to some extent.