@misc{Lexicon of Arguments, title = {Quotation from: Lexicon of Arguments – Concepts - Ed. Martin Schulz, 29 Mar 2024}, author = {Mayr,Ernst}, subject = {Individuals}, note = {I 205 Formation of Individuals/Biology/Mayr: Def Parthenogenesis: Asexuality: in some organisms, individuals develop themselves from the eggs, fertilization is not necessary. E.g. Aphids, plankton crustaceans: here sexual and asexual generations alternate. I 206 Sexuality: increases diversity and thus defense against diseases. I 207 Pangenesis theory: (old) theory, according to which each body cell contributes hereditary material. From Aristotle to the 19th century. PreformationVsEpigenesis (already in Aristotle, then to the nineteenth century). I 208 VsAristotle: Aristotle believed falsely, only female organisms could possess eggs. >Aristotle. I 209 Egg: the actual mammal was discovered only by Karl Ernst von Baer in 1828(1). It was recognized that the ovary is the counterpart to the testis. DNA: discovered by Johann Friedrich Miescher (19th century). I 211 Definition Preformation: Eggs produce individuals of the same species. Therefore it was concluded that egg or sperm is already a miniature of the future organism. Logical consequence: in this organism all future offspring must again be contained in a miniature edition (nesting). Numerous contemporary pictures did show such small miniature humans (homunculi) in the spermatozoon. I 212 Epigenesis: thought that the development came from an entirely unformed mass. "Vis essentialis." Each species has its own peculiar "essential force". This was completely opposed to the uniform forces described by the physicists, e.g. gravitation. Definition Epigenesis: Development during the life history of the individual, in contrast to ontogeny and phylogeny. Nevertheless, the epigenesis prevails in the controversy. Solution only in the 20th century: difference between Definition genotype (genetic constitution of the individual) and Definition phenotype (totality of perceptible characteristics). Cell: how does it come that the nerve cell develops so completely differently as a cell of the digestive tract? I 214 Cell division: Wilhelm Roux (1883)(2) concludes the complex internal differentiation of the cell: Solution: particles must be placed on a thread, and this is divided! Confirmed later. Cell: passes through a differentiation process, only a small part of the genes in the nucleus is active. Cell development: in taxa with regulatory development (e.g. vertebrate animals) there are no fixed early cell lines, but extensive cell migration. Induction (influence of already existing tissues on the development of other tissues) largely determines the specification of the cells. Cell migration: pigment and nerve cells make extensive migrations through the organism. Often they follow clear chemical stimuli. 1. E. v. Baer (1828). Entwickelungsgeschichte der Thiere: Beobachtung und Reflexion. Königsberg: Bornträger. 2. W. Roux (1883). Über die Bedeutung der Kerntheilungsfiguren. Leipzig: Engelmann.}, note = { Mayr I Ernst Mayr This is Biology, Cambridge/MA 1997 German Edition: Das ist Biologie Heidelberg 1998 }, file = {http://philosophy-science-humanities-controversies.com/listview-details.php?id=445261} url = {http://philosophy-science-humanities-controversies.com/listview-details.php?id=445261} }