How did Dobzhansky and Mayr explain the origin of species?

Updated: 8/10/2023

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In the 1930s, Dobzhansky and Mayr explained that species originate through allopatric speciation.

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What is the biological species concept of Ernest Mayr?

Mayr's definition of a species is based on the genetic isolation of populations.A ... difficulty which confronts us in our attempt at a species definition is thatthere is, in nature, a great diversity of different kinds of species. Even if we donot consider such aberrant phenomena as the apomictic species in plants andthe strains of bacteria, there is, even among animals, a great variety of differenttaxonomic situations which are generally classified as species. The question as towhether the species of birds, of corals, or protozoa, and of intestinal worms arethe same kind of evolutionary phenomena is entirely justified. . . It may not be exaggeration if I say that there are probably as many species concepts as there arethinking systematists and students of speciation. [(Mayr 1942: 114-115)]A species consists of a group of population which replace each othergeographically or ecologically and of which the neighboring ones intergradeor interbreed wherever they are in contact or which are potentially capable ofdoing so (with one or more of the populations) in those cases where contact isprevented by geographical or ecological barriers.Or shorter: Species are groups of actually or potentially interbreedingnatural populations, which are reproductively isolated from other such groups.[Systematics and the Origin of Species, 1942: 120]

How does the existence of an archipelago promote speciation?

An archipelago is basically a group of islands. Speciation according to the Biological Species Concept by Ernest Mayr, is -- populations whose members can interbreed and produce viable, fertile offspring. For example, the Galapagos finches studied by Charles Darwin. Some live on different parts of the archipelago and so have different features, adapting to their environment. These different feature obviously get passed down and are more frequent in future populations because those finches with this specific adaptation lived and reproduced better. So since there are different islands, there are different finch speciation and so the geographic isolation promotes speciation.

Who are all Cytologists and their contribution?

Visual discovery of chromosomes. Textbooks have often said that chromosomes were first observed in plant cells by a Swiss botanist named Karl Wilhelm von Nägeli in 1842.[1] However, this opinion has been challenged, perhaps decisively, by Henry Harris, who has freshly reviewed the primary literature.[2] In his opinion the claim of Nägeli to have seen spore mother cells divide is mistaken, as are some of his interpretations. Harris considers other candidates, especially Wilhelm Hofmeister, whose publications in 1848-9 include plates which definitely show mitotic events.[3][4] Hofmeister was also the choice of Cyril Darlington. The work of other cytologists such as Walther Flemming, Eduard Strasburger, Otto Bütschli, Oskar Hertwig and Carl Rabl should definitely be acknowledged. The use of basophilic aniline dyes was a new technique for effectively staining the chromatin material in the nucleus. Their behavior in animal (salamander) cells was later described in detail by Walther Flemming, who in 1882 "provided a superb summary of the state of the field".[5][6] The name chromosome was invented in 1888 by Heinrich von Waldeyer. However, van Beneden's monograph of 1883 on the fertilised eggs of the parasitic roundworm Ascaris megalocephala was the outstanding work of this period.[7] His conclusions are classic: * Thus there is no fusion between the male chromatin and the female chromatin at any stage of division... * The elements of male origin and those of female origin are never fused together in a cleavage nucleus, and perhaps they remain distinct in all the nuclei derived from them. [tranl: Harris p162] "It is not easy to identify who first discerned chromosomes during mitosis, but there is no doubt that those who first saw them had no idea of their significance... [but] with the work of Balbiani and van Beneden we move away from... the mechanism of cell division to a precise delineation of chromosomes and what they do during the division of the cell." [8] Van Beneden's master work was closely followed by that of Carl Rabl, who reached similar conclusions. [9] This more or less concludes the first period, in which chromosomes were visually sighted, and the morphological stages of mitosis were described. Coleman also gives a useful review of these discoveries.[10] Nucleus as the seat of heredity. The origin of this epoch-making idea lies in a few sentences tucked away in Ernst Haeckel's Generelle Morphologie of 1866.[11] The evidence for this insight gradually acumulated until, after twenty or so years, two of the greatest in a line of great German scientists spelt it out. August Weismann proposed that the germ line was separate from the soma, and that the cell nucleus was the repository of the hereditary material, which he proposed was arranged along the chromosomes in a linear manner. Furthermore, he proposed that at fertilisation a new combination of chromosomes (and their hereditary material) would be formed. This was the explanation for the reduction division of meiosis (first described by van Beneden). Chromosomes as vectors of heredity. In a series of outstanding experiments, Theodor Boveri gave the definitive demonstration that chromosomes were the vectors of heredity. His two principles were: : The continuity of chromosomes : The individuality of chromosomes. It was the second of these principles which was so original. He was able to test the proposal put forward by Wilhelm Roux, that each chromosome carries a different genetic load, and showed that Roux was right. Upon the rediscovery of Mendel, Boveri was able to point out the connection between the rules of inheritance and the behaviour of the chromosomes. It is interesting to see that Boveri influenced two generations of American cytologists: Edmund Beecher Wilson, Walter Sutton and Theophilus Painter were all influenced by Boveri (Wilson and Painter actually worked with him). In his famous textbook The Cell, Wilson linked Boveri and Sutton together by the Boveri-Sutton theory. Mayr remarks that the theory was hotly contested by some famous geneticists: William Bateson, Wilhelm Johannsen, Richard Goldschmidt and T.H. Morgan, all of a rather dogmatic turn of mind. Eventually complete proof came from chromosome maps - in Morgan's own lab! [12]