self-organization
Catalysts are chemical substances that modify reaction rates without themselves being changed in the process. Their kinetics are characterized by threshold and amplification phenomena. Enzymes are the major class of biological catalysts.
Read MoreAutopoesis is both a concept about self-maintaining systems, especially biological ones, and an epistemological theory about cognition and self-reference.
Read MoreChemical reactions do not generally display dynamic patterns or spatial order. The Belousov-Zhabotinsky reaction, discovered in 1951, may be the first completely understandable laboratory example of pattern formation in a chemical system that involves nothing more than chemical reaction and molecular diffusion. That same year, in 1951, Alan Turing investigated the theoretical possibilities of pattern formation by reaction/diffusion as "The chemical basis of Morphogenesis." The B/Z reaction is an example of a chemical system that shows spatial, periodic and wave properties that suggests that morphogenetic self-organization might follow similar pathways in both inorganic and organic systems. (cf. Slime Mold)
from Arthur T. Winfree, When Time Breaks Down, p. 168
The modern awakening of interest in complexity as a science began in Vienna in 1928, with Ludwig von Bertalanffy's largely descriptive graduate thesis on living organisms as systems. A few years earlier Alfred North Whitehead had described his similar vision of a "philosopy of organism" in Science and the Modern World. Whitehead describes his theory of the organic conception of nature as based on "self-knowledge of our bodily event." This total bodily event is on the same level as all other events, except for an unusual complexity and stability of inherent pattern. (Science and the Modern World, p. 73)
Read MoreDevelopment is the process that transforms an egg into a growing embryo and eventually into an adult form.
How is this process to be understood? According to Scott Gilbert, the aesthetic of embryology separates it from other areas of biology. It is an aesthetic informed by the ordered, directional change manifest during the life of individual organisms, as they develop from a single, fertilized egg into complex patterns of diifferent, yet interacting cell, tisssues, and organs.
A few questions have dominated the study of embryology:
First of all, how is the extraordinary process of development regulated? How does a single-celled organism turn into a highly differentiated one with millions or even billions of cells? Do Genes control development? see genotype / phenotype
Is the final form of the organism set from the start? Or are there different paths of development available to the embryo? (For a discussion of preformism and epigenesis, see epigenesis}
What is the relation between the sequence of development and the process of evolution? Why do embryos of different species look so similar, and how do they end up so different?
Read MoreHow can a cell "know" to respond to the presence or absence of an enzyme? What is it that induces genes to work only when needed?
Using a fine baby's hair, taken from his own daughter, Hans Spemann tied off and separated the two halves of a two-celled newt embryo. The cells on either side of the knot gave rise to normal newt tadpoles. When Spemann divided the egg differently, by tying it perpendicular to the furrow between the two cells of the embryo, he obtained a dramatically different result. Only one side made a normal tadpole, while the other made a disorganized mass of belly tissue. This eventually lead to the recognition that a region of the embryo, called the dorsal lip of the blastopore, was critical for the organization of the embryo. If this region of the embryo was removed, the embryo formed a blob of tissue lacking structures that normally form on the top (dorsal) side of the animal. In 1924, Spemann proved that a graft could induce host tissues adjacent to it to completely change their fate and to form a second embryo in relation to the graft. If the dorsal lip was transplanted to the presumptive belly region of another developing embryo, it organized a second embryonic axis, and two embryos formed that were joined together. Spemann dubbed this region the "organizer" because he deduced that it organized the dorsal parts of the embryo into neural structures and could induce development of another embryonic axis. All organizers share the property of influencing the formation of pattern, or morphogenesis, in tissues or cells. The basic interpretation of their special activity is that the cells of organizers produce substances that can influence the development of other cells. Such substances have been dubbed morphogens. It has long been thought that morphogens produced in one site diffuse outward and form concentration gradients from their source. The idea then is that cells surrounding the source respond to the amount of morphogen they experience. The affected area is also called the zone of polarizing activity (ZPA). Recent advances in embryology have correlated these zones with the expression of specific genes (toolkit genes)
Read More"In order to adequately understand their apparently idiosyncratic contributions... riddled with jargon and with a mysteriously ineffable systematicity..." (E. Grosz)
Describing the development of weapons such as the saber or the sword, Deleuze and Guattari relate how metallurgy follows variations in materials and their qualities (spatio-temporal haecceities) and transforms them into features (traits of expression) such as hardness, sharpness and finish.
"We may speak of a machinic phylum or technological lineage, wherever we find a constellation of singularities , prolongable by certain operations, which converge, and make the operations converge, upon one or several assignable traits of expresssion" ..."Each phylum has its own singularities and operations...which determine the relation of desire to the technical element."...
"We will call an assemblage every constellation of singularities and traits deducted from the flow of matter-movement. The assemblages cut the phylum up into distinct, differentiated lineages, at the same time as the machinic phylum cuts accross them all." (Thousand Plateaus, p. 406) Examples of these assemblages include the nomads' invention of the man-horse-bow assemblage.
"The machinic phylum is materiality, natural or artificial, and both simultaneously; it is matter in movement, in flux, in variation, matter as a conveyor of singularities and traits of expression...This matter flow can only be followed. The artisan is one who is determined to follow a flow of matter as pure productivity. The artisan is the itinerant, the ambulant. His work is a legwork. To follow the flow of matter...is intuition in action." (p.409) (this is neither nomadic nor sedentary, but in contact with both) -- minor science.
"Why is the machinic phylum, the flow of matter, essentially metallic, or metallurgical?" (p 410) "Metallurgy is the consciousness or thought of the matter-flow...The machinic phylum is metallurgical, or at least has a metallic head, as its itinerant probe-head or guidance device." In this respect, Deleuze and Guattari follow the trope established by the Futurists and followed by the architectural avant-garde, that described engineers as noble savages at the vanguard of technological innovation, "men of the people without culture or education," endowed with "the gift of mechanical prophecy, the flair for metals." (Marinetti, Le Futurisme, Quoted in Reyner Banham, A Concrete Atlantis, p.204)
According to Manuel de Landa, for Deleuze the machinic phylum is the overall set of self-organizing processes... in which a group of previously disconnected elements suddenly reaches a criticial point in which they begin to "cooperate" to form a higher entity. The notion of a machinic phylum blurs the distinction between organic and non-organic life. Phenomena of self-organization occur whenever a bifurcation takes place in phase space: when a new attractor appears or when the system's attractors mutate in kind.
According to de Landa, Deleuze realized the philosophical implications of trajectories, attractors, and bifurcations in phase space . He emphasized the ontological difference between "actual physical systems" (represented by trajectories in phases space), and "virtual physical systems" represented by attractors and repellors. Although he did not mention bifurcations by name, he explored the idea that special events could produce "an emission of singularities", that is, the sudden creation of a set of attractors and repellors. Thus in addition to "actual machines", there are two layers of "virtual machines" . The world of attractors (the first layer) defines the long-term tendencies of reality. The world of bifurcations modifies those tendencies and represents the source of creativity and variability in nature. (see de Landa p. 236 and Deleuze Logic of Sense)
A field is a region of physical influence. Fields are not a form of matter, rather, matter is energy bound within fields. In current physics, several kinds of fundamental fields are recognized: the gravitational and electro-magnetic fields and the matter fields of quantum physics.
The field concept in biology has its origin in the work of Hans Driesch, although the concept itself was elaborated by A. Gurwitsch and P. Weiss. (see account in Gerry Webster and Brian Goodwin, Form and Transformation, pp 94-100) For Joseph Needham, fields are "wholes actively organizing themselves."
In the last decade of the nineteenth century, the embryologist Wilhelm Roux proposed a "developmental mechanics" (Entwicklungsmechanik ) to account for origin and maintenance of organisms through a causal morphology that would reduce them to a "movement of parts," and would prove that biology and physics were completely one with each other. Roux sought to transform biology from a purely historical into a causal discipline through analytic thought and experiment. His "mosaic theory" described development as the self-differentiation of hereditary potentialities with the irreversible functional differentiation among cells. This hypothesis was supported in part by Roux's own experiments at the marine biological station in Naples. When he killed one of the first two cleavage cells in a frog's egg, the surviving cell, as he expected, gave rise to only half of a normal embryo.
in 1891, while working at the Naples station with a different organism, Hans Driesch obtained radically different results. Driesch demonstrated that, contrary to the Roux-Weismann hypothesis, each cell of a sea urchin embryo, when isolated at the two-cell stage, does not produce a half-embryo but a complete, miniature pluteus larva of normal form. (see mechanism / vitalism for philosophical interpretations of these experiments.)
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