Synthetic theory of evolution презентация

Synthetic theory of evolution. Medical Academy named after S.I. Georgievsky of Vernadsky CFU. Department of Biology.

Introduction:- The synthetic theory of evolution is considered the most unifying theory of life science. This theory is mainly based on neo-Darwinism, particularly on Mendelism, population genetics, mutations, natural selection, gradualism, and the central dogma of molecular biology. These are key topics to explain genome changes, speciation phenomena, and biodiversity. Neo-Darwinism roots are found in August Weissmann's theory of continuity of the germplasm. Weismann established that organisms have two sets of cells: somatoplasm and germplasm. In the latter, there are particles or biospheres associated with chromosomes responsible for the transmission of inherited characters. Thus, Weismann laid the foundations of chromosome theory of inheritance. He rejected Lamarck's theory of acquired characteristics, and challenged all these ideas of the natural selection theory of Charles Darwin. Thus, Neo-Darwinism emerged, by adding Weismann's theory of the continuity of germplasm

Continue…. The rediscovery of the principles of Mendel by Hugo de Vries, Carl Correns and Erich Von Tschermak strengthened Neo-Darwinism, and with the contributions of Fisher, Wright, Haldane, Dobzhansky, Mayr, Simpson, Stebbins and Huxley, "Population Genetics" and "The Synthetic Theory of Evolution" emerged. Since its origins, this theory has dominated the minds and thoughts of scientists in explaining the mechanisms involved in the phenomenon of speciation. However, important omissions have prevented a full understanding of the processes involved in organic evolution. Especially, there is little consideration regarding: 1) the lack of a bridge between somatic and germinal eukaryote cells, 2) lateral genetic transferences performed by plasmids and viruses in the genome of eukaryotes, 3) the lack of a holistic concept of the gene, determinism, and genetic reductionism, 4) non-coding DNA, 5) epigenesis, 6) homeotic mutations and the genetics of development, and 7) sympatric speciation.

Modern synthetic theory of evolution. (NEO-DARWINISM). Modern evolutionary theory is based on combining the theory of De Vrie's mutations with Darwin's theory of natural selection leading to descent with modification. ... The Neo Darwin or Modern synthesis is dependent on the concept of mutations creating new information The Modern Synthetic theory of Evolution showed a number of changes as to how the evolution and the process of evolution are conceived. The theory gave a new definition about the evolution as “the changes occurring in the allele frequencies within the populations, ” which emphasizes on the genetics of evolution.

MODERN SYNTHESIS (NEO DARWINISM):- The fusion of Mendelian genetics and Darwin's natural selection Produce a more comprehensive evolutionary theory than either can offer separately Darwin showed that evolution involves selection interacting with variation within populations Mendel that the bases of this variation are discrete units of heredity (genes) Neo Darwinism Supporters:- Romanes, Wallace, Fisher, Huxley, Ford, Haldane, Goldschmidt, Sewall Wright, Ernst Haeckel, August Weismann, Mendel, Dobazhansky, Kettlewell and Herbert Spencer

Darwinism vs Neo-Darwinism. Darwinism Considers all inheritable favourable variation Does not explain the reason for variation The basic unit of evolution is an individual Does not consider reproductive isolation as a major factor in new species formation. Natural selection is the survival of the fittest and removal of the unfit ones during the course of time

CONTINUE…. Neo-Darwinism-  The modification of original concept postulated by Darwin and Wallace based on data obtained from genetic research  Considers only inheritable genetic variation (mutations) for evolution  Explains the reason for variations  The basic unit of evolution is a population  Consider reproductive isolation as a major essential factor in speciation  Natural selection refers to the differential reproduction leading to the changes in gene frequency

FACTORS AFFECTING MODERN THEORY OF EVOLUTON. Recombination or Variation:- Recombination of the new genotypes from the existing genes. The gene combinations having same indi­viduals with two kinds of alleles, mixing of the chromosomes during sexual reproduc­tion of two parents produce new individuals, an exchange of the chromosomal pairs of alleles during the meiosis which is called crossing overproduce the new form of gene combinations. Chromosomal mutations like deletion, inversion, duplication, translocation, polyploidy result in the recombination. The random mixing of chromosomes from two parents during sexual reproduction to produce a new individual . The exchange between chromosomal pairs of particular alleles during meiosis. Called crossing over, to produce new gene combinations.

Mutation:- Mutation:- The changes that occur in the gene due to phenotypic effect differential as the mutation. This produces a variety of changes that may be harmful. Many of the mutant forms of genes are recessive to the normal genes in a homozygous condition. These mutations cause variations in offsprings. Alteration in the chemistry of gene (DNA) is able to change its phenotypic effect Called point mutation or gene mutation. Mutation can produce drastic changes. May be deleterious or harmful and lethal or can remain insignificant. There are equal chances of a gene to mutate back to normal. Most of the mutant genes are recessive to normal gene able to express phenotypically only in homozygous condition

Heredity:- The transmission occurring in the variations from the parents to their offsprings is a primary mechanism in the evolution. The organisms which possess hereditary properties are favoured in the struggle for the existence. By this, the offsprings benefit from the characteristics of parents. The transmission of variations from parent to offspring is an important mechanism of evolution Organisms possessing helpful hereditary characteristics are favored in the struggle for existence he offspring's are able to benefit from the advantageous characteristics of their parents

Natural selection:- Natural selection:- Natural selection produces a change in the frequency of the genes from one generation to the other favoring the differential form of the reproduction. The natural selection process creates an adaptive relation between the environment and the population through various combinations of genes. Brings evolutionary change by favouring differential reproduction of genes Produces change in gene frequency from one generation to the next Does not produce genetic change, but once it has occurred it acts to encourage some genes over others. Creates new adaptive relations between population and environment. By favouring some gene combinations, rejecting others and constantly modifying and molding the gene pool

Isolation:- It is one among the significant factors responsible for the synthetic theory of evolution. The isolation helps in preventing the interbreeding of related organisms which is a reproductive form of isolation. Isolation of organisms of a species into several populations or groups under psychic, physiological or geographical factors is supposed to be one of the most significant factors responsible for evolution. Geographical barriers include physical barriers , Rivers, oceans, high mountains which prevent interbreeding between related organisms. Physiological barriers help in maintaining the individuality of the species. The isolations known as reproductive isolation do not allow the interbreeding amongst the organisms of different species

DARWINISM:- Charles Darwin’s important postulates- Over production Struggle for existence Variations Survival of the fittest Origin of species

Links for better understanding https://www.youtube.com/watch?v=gD_-j9LfaQM https://www.youtube.com/watch?v=zuJtLlk598Y https://www.youtube.com/watch?v=yfzKGtffqNY https://www.youtube.com/watch?v=9BCmjNxjoVg