Embryon drawing is an embryo illustration in the order of their development. In plants and animals, embryos develop from a zygote, a single cell produced when eggs and sperm combine during fertilization. In animals, the zygote divides repeatedly to form cell spheres, which then form a set of migrating tissue layers and fold to form the initial embryo. The embryo image provides a means to compare embryos of different ages, and species. To this day, embryo drawings are made in the biology lessons of undergraduate development.
Comparing different stages of embryos from different animals is a tool that can be used to infer relationships between species, and thus biological evolution. This has been a source of considerable controversy, both now and in the past. Ernst Haeckel pioneered in this field. By comparing the different embryonic stages of different vertebrate species, he formulates the recapitulation theory. This theory states that the development of animal embryos follows exactly the same sequence as their evolutionary ancestors. Haeckel's work and subsequent controversies link the fields of developmental biology and comparative anatomy to comparative embryology. From a more modern perspective, Haeckel's image is the beginning of the field of evolutionary evolutionary biology (evo-devo).
The study of comparative embryology aims to prove or disprove that vertebrate embryos of different classes (eg mammals vs. fish) follow the same developmental path because of their common ancestors. Such developing vertebrates have the same genes, which determine the basic plan of the body. However, further development makes it possible to distinguish different characteristics as adults.
Video Embryo drawing
Use of embryo and photographic images in contemporary biology
In current biology, fundamental research in evolutionary developmental biology and evolutionary biology is no longer driven by morphological comparisons between embryos, but rather by molecular biology. This is partly because Haeckel's image is very inaccurate.
Maps Embryo drawing
Controversy
The precision of the embryonic images of Ernst Haeckel has caused much controversy among recent proponents of Intelligent Design and intellectual opponents of Haeckel in the past. Although the early embryos of different species show similarity, Haeckel seems to exaggerate this similarity in favor of his recapitulation theory, sometimes known as Biogenetic Law or "Ontogeny recapitulates phylogeny". Furthermore, Haeckel even proposes theoretical life forms to accommodate certain stages in embryogenesis. A recent review concluded that "biogenetic law is supported by several recent studies - if applied to only one character".
Critics in the late 19th and early 20th centuries, Karl von Baer and Wilhelm His, do not believe that living embryos reproduce the evolutionary process and produce their own embryonic images that emphasize differences in early embryological development. The critics of the 20th and early 21st century, Stephen Jay Gould, object to continuing to use Haeckel's embryo image in textbooks.
On the other hand, Michael K. Richardson, Professor of Evolution for the Development of Zoology, University of Leiden, while acknowledging that some criticism of the image is legitimate (indeed, it was he and his co-workers who embarked on modern criticism in 1998), having supported the image as a teaching aid , and says that "at the basic level, Haeckel is right"
src: kcct.org
famous embryo illustrator
Ernst Haeckel (1834-1919)
Haeckel's illustration shows the vertebrate embryo at various stages of development, which shows the embryo's similarity as support for evolution, recapitulation as evidence of Biogenetic Law, and phenotypic differences as von Baer's legal proof. A series of twenty-four embryos from the earliest edition of Haeckel's Anthropogenie remain the most famous. Different species are arranged in columns, and different stages in rows. The similarities can be seen along the first two lines; The appearance of special characters in each species can be seen in the columns and the diagonal interpretation brings one to Haeckel's recapitulation idea.
Haeckel's embryo pictures are primarily intended to express the idiosyncratic theory of embryonic development, Biogenetic Law, which in turn assumes (but is not essential to) the evolutionary concept of the common ancestry. His opinion about embryonic development coincides with his understanding of evolution as a process of development. In and around 1800, embryology integrates with comparative anatomy as the main foundation of morphology. Ernst Haeckel, along with Karl von Baer and Wilhelm His, was especially influential in shaping the early foundations of 'phylogenetic embryology' based on the principle of evolution. Haeckel's 'Biogenetic Law' describes the parallel relationship between embryonic development and phylogenetic history. The term, 'recapitulation,' has become part of Haeckel's Biogenetic Law, for embryonic development is the recapitulation of evolution. Haeckel proposes that all vertebrate classes go through an evolutionary "phylotypic" development stage, a period of phenotypic diversity reduction between higher embryos. Only in subsequent developments do certain differences arise. Haeckel describes the concrete demonstration of his Biogenetic Law through the theory of 'Gastrea', in which he argues that the early stages of a cup-shaped gastrula are a universal feature of many celled animals. The ancestral form exists, known as gastrea, which is the common ancestor of the corresponding gastrula.
Haeckel argues that certain features in embryonic development are eternal and most sensitive, while others are caenogenetic. Caenogenesis represents a "blurring of the ancestral similarities in development," which is said to be the result of a particular adaptation to the life of the embryo due to environmental changes. In his drawings, Haeckel cites notochords, curves of pharynx and crevices, pronefros and neural tubes as spectacular features. However, egg yolk sacs, extra-embryonic membranes, egg membranes and tubal endocardials are considered as caenogenetic features. The addition of the terminal adult stage and telescoping, or driving back, the stages to the embryonic stage of descent are also representative of the development of the Haeckelian embryo. In alluding to the image of the embryo to the public, Haeckel does not cite any source, which gives his opponent the freedom to make assumptions about the originality of his work. Karl Ernst von Baer (1792-1876)
Haeckel is not the only one who created a series of images representing embryonic development. Karl E. von Baer and Haeckel struggled to model one of the most complex problems facing embryologists at the time: general and specific character setting during development in various animal species. Due to the development of time, the von Baer development scheme is different from Haeckel's scheme. The Von Baer development scheme does not need to be associated with a development stage determined by a particular character, where recapitulation involves heterokronik. Heterochrony represents a gradual change in the original phylogenetic sequence due to embryo adaptation. In addition, von Baer early noted that the embryos of different species can not be easily distinguished from one another as in adults.
The Von Baer Act that governs embryonic development is a specific rejection of recapitulation. In response to Haeckel's recapitulation theory, von Baer pronounces his most famous developmental law. The law of Von Baer states that the general features of animals appear earlier in embryos rather than special features, where less common features come from the most common, any embryo of a species more and more distant from that part has been determined through the stages of other animals, and there is never a complete morphological similarity between the embryo and the lower adult. Von Baer's embryo image shows that individual development comes from the common features of embryos that are developing at an early stage through differentiation into special features specific to species, establishing that linear evolution can not occur. The embryological development, in von Baer's mind, is a process of differentiation, "a movement from a more homogeneous and universal to a more heterogeneous and individualized one."
Von Baer argues that embryos will resemble each other before achieving characteristics that distinguish them as part of a particular family, genus or species, but the embryo is not the same as the lower end of the organism.
Wilhelm_His_ (1831-1904) "> Wilhelm His (1831-1904)
The debate between Haeckel and His eventually becomes fueled by the description of the embryo that Wilhelm Krause pushes directly into the ongoing feud between Haeckel and His. Haeckel speculates that allantois are formed in the same way in humans and other mammals. He, on the other hand, accuses Haeckel of changing and playing with facts. Although Haeckel was proved right about allantois, the use of the Krause embryo as justification turned out to be problematic, since the embryo was a bird rather than a human. The underlying debate between Haeckel and His comes from a different perspective on the similarity or inequality of vertebrate embryos. In response to Haeckel's evolutionary assertion that all vertebrates are essentially identical in the first months of embryonic life as evidence of common descent, his response by insisting that more skilled observers will soon recognize that early embryos can be distinguished. He also counteracts Haeckel's picture sequence in Anthropogenie with what he calls "exact" pictures, highlighting specific differences. In the end, He went so far as to accuse Haeckel of "faking" his parable embryo to make the vertebrate embryo look more alike than it is in reality. He also accused Haeckel of creating the early human embryo he described in his imagination rather than obtained through empirical observation. He completed his accusation of Haeckel by stating that Haeckel had "'relinquished the right to count as an equivalent in a serious research company.'"
Opposition to Haeckel
Haeckel underwent many contradictions to the artistic depiction of embryonic development in the late nineteenth and early twentieth centuries. Opponents Haeckel believes that he does not emphasize the difference between the early embryonic stages to make the similarity between the embryos of different species more pronounced.
Initial opponent: Ludwig Rutimeyer, Theodor Bischoff and Rudolf Virchow
The first suggestion of the forgery of Haeckel was made in late 1868 by Ludwig Rutimeyer at the Archiv fÃÆ'¼r Anthropogenie. Rutimeyer is a professor of zoology and comparative anatomy at the University of Basel, who rejects natural selection as simply mechanistic and proposes an anti-materialist view of nature. Rutimeyer claims that Haeckel "has taken the kind of freedom with established truth." Rutimeyer claims that Haeckel presents the same image three times in a row as a forerunner to dogs, chickens, and turtles. Although Rutimeyer does not denounce Haeckel's embryo image as a fraud, he argues that such a picture is a manipulation of public and scientific thought.
Theodor Bischoff (1807-1882), was a strong opponent of Darwinism. As a pioneer in mammalian embryology, he is one of Haeckel's strongest critics. Although the 1840 Bischoff survey illustrates just how similar the early human embryo to other vertebrates, it then demands that the hasty generalization be inconsistent with its recent findings about the inequality between hamster and embryo and dog embryos. However, Bischoff's main argument refers to Haeckel's image of a human embryo, since Haeckel is later accused of obscuring a dog's embryo from him. Throughout Haeckel's time, criticism of embryonic images is often caused by his critics' belief in the representation of his embryological development as a "rough schemata." In this way, Haeckel specifically selects the relevant features to be depicted in his picture. Haeckel's opponents find his method problematic because of simplicity such as removing certain structures that distinguish between higher and lower vertebrates. In 1877, Rudolf Virchow (1821-1902), who had been an inspiration for Haeckel in WÃÆ'¼rzburg, proclaimed that Haeckel's embryo image represents a mere hypothesis.
Haeckel's contemporary criticism: Michael Richardson and Stephen Jay Gould
Michael Richardson and his colleagues in the July 1997 edition of Anatomy and Embryology, showed that Haeckel slandered his image to exaggerate the phylotypic phase similarity. In the March 2000 issue of Natural History , Stephen Jay Gould argues that Haeckel "exaggerates the equation with idealization and neglect." In addition, Gould argues that Haeckel's image is inaccurate and falsified. On the other hand, one of those who criticized Haeckel's picture, Michael Richardson, argues that "Haeckel's much criticized image is important as a phylogenetic hypothesis, props, and evolutionary evidence". But even Richardson admitted in 1997 that his team's investigation of Haeckel's image showed them to be "one of the most famous fakes in biology."
Several versions of Haeckel's drawings can be found in many modern biology textbooks in the discussion of the history of embryology, with clarifications that these are no longer considered valid.
Haeckel's proponents (past and present)
Although Charles Darwin received Haeckel's support for natural selection, he was tentative in using Haeckel's ideas in his writings; With regard to embryology, Darwin relies heavily on the work of von Baer. Haeckel's work was published in 1866 and 1874, years after Darwin's "The Origin of Species" (1859).
Despite many contradictions, Haeckel has influenced many disciplines in his field in an effort to integrate the disciplines of taxonomy and embryology into the Darwinian framework and to investigate phylogenetic reconstruction through its Biogenetic Law. In addition, Haeckel serves as a mentor to many important scientists, including Anton Dohrn, Richard and Oscar Hertwig, Wilhelm Roux, and Hans Driesch.
One of Haeckel's early supporters was Carl Gegenbaur at the University of Jena (1865-1873), where both men absorbed the impact of Darwin's theory. Both quickly attempted to integrate their knowledge into the evolution program. In determining the relationship between "phylogenetic relations" and "laws of form evolution," both Gegenbaur and Haeckel depend on the method of comparison. As Gegenbaur says, the task of comparative anatomy lies in the explanation of animal body shape and organization to provide evidence for the continuity and evolution of a series of organs in the body. Haeckel then provides the means to achieve this goal with his biogenetic law, in which he proposes to compare the various stages of individual development with his ancestral line. Although Haeckel emphasizes comparative embryology and Gegenbaur promotes comparison of adult structures, both believe that both methods can work together to produce evolutionary morphological aims.
Philologist and anthropologist, Friedrich Müller, uses Haeckel's concept as a source for his ethnological research, involving a systematic comparison of folklore, beliefs and practices of different societies. MÃÆ'¼ller's work relies heavily on theoretical assumptions that are very similar to Haeckel and reflects German practice to maintain a strong relationship between empirical research and the philosophical framework of science. Language is very important, because it bridges between the natural sciences and philosophy. For Haeckel, language specifically represents the concept that all phenomena of human development are related to the laws of biology. Although MÃÆ'¼ller does not particularly have an influence in advocating Haeckel's embryo image, both share a common understanding of the development from lower form to higher form, since MÃÆ'¼ller specifically sees humans as the last link in the endless chain of evolutionary development.
Modern Acceptance of Haeckel's Biogenetic Law, despite the rejection of Haeckelian's current view, finds support in some degree of parallelism between ontogeny and phylogeny. A. M. Khazen, on the one hand, states that "ontogeny must repeat the main phylogeny." A. S. Rautian, on the other hand, argues that the reproduction of patterns of ancestral development is a key aspect of a particular biological system. Dr. Rolf Siewing recognizes the similarity of embryos in different species, together with von Baer's law, but does not believe that one should compare embryos with the stage of adult development. According to M. S. Fischer, the review of Biogenetic Law is possible as a result of two fundamental innovations in biology since Haeckel's time: cladistics and developmental genetics.
To preserve Haeckel's embryo image, his main argument is "schematisation." Haeckel's drawings are not intended to represent a technical and scientific, but rather schematic drawings and reconstruction specifically for lay audiences. Therefore, as R. Gursch says, Haeckel's embryo image should be considered "reconstruction." Although the picture is open to criticism, the image should not be considered to be falsifying anything. Although modern defenses of Haeckel's embryonic image still consider the inaccuracy of the images, the allegations of fraud are considered unreasonable. As Erland NordenskiÃÆ'¶ld says, fraud charges against Haeckel are not necessary. R. Bender finally stepped away to reject his claims concerning the manufacture of certain developmental stages in Haeckel's drawings, on the grounds that Haeckel's embryo drawings is a faithful representation of the real stages of embryo development compared to embryos that are published.
Survival and reproduction of Haeckel's embryo drawings
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