Bow tie (biology)
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In the biological sciences, the term ''bow tie'' (so called for its shape) is a recent concept that tries to grasp the essence of some operational and functional structures observed in biological organisms and other kinds of
complex Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...
and
self-organizing Self-organization, also called spontaneous order in the social sciences, is a process where some form of overall order and disorder, order arises from local interactions between parts of an initially disordered system. The process can be spon ...
systems. In general, bow tie architectures refer to ordered and recurrent structures that often underlie complex technological or biological systems, and that are capable of conferring them a balance among efficiency, robustness and evolvability. In other words, bow ties are able to take into account a great diversity of inputs (fanning in to the knot), showing a much smaller diversity in the protocols and processes (the ''knot'') able to elaborate these inputs, and finally an extremely heterogeneous diversity of outputs (fanning out of the bowtie). These architectures thus manage a wide range of inputs through a ''core'' (knot) constituted by a limited number of elements. In such structures, inputs are conveyed into a sort of funnel, towards a " synthesis"
core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the centra ...
, where they can be duly organized, processed and managed by means of protocol

and from where, in turn, a variety of outputs, or responses, is propagated. image:general bowtie architecture.png, scheme of a general bow tie architecture According to Csete and Doyle, bow ties are able to optimally organize fluxes of mass, energy, signals in an overall structure that forcedly deals with a highly fluctuating and "sloppy" environment. In a biological perspective, a bow tie manages a large ''fan in'' of stimuli (input), it accounts for a "compressed" ''core'', and it expresses again a large ''fan out'' of possible
phenotypes In genetics, the phenotype () is the set of observable characteristics or phenotypic trait, traits of an organism. The term covers the organism's morphology (biology), morphology or physical form and structure, its Developmental biology, dev ...
, metabolite products, or –more generally – reusable modules. Bow tie architectures have been observed in the structural organization at different scales of living and
evolving Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
organisms (e.g. bacterial
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...
network) as well as in technological and dynamical systems (e.g. the Internet). Bow ties seem to be able to mediate trade-offs among
robustness Robustness is the property of being strong and healthy in constitution. When it is transposed into a system, it refers to the ability of tolerating perturbations that might affect the system’s functional body. In the same line ''robustness'' ca ...
and efficiency, at the same time assuring to the system the capability to evolve. Conversely, the same efficient architecture may be prone and vulnerable to fragilities due to specific changes, perturbations, and focused attacks directed against the core set of modules and protocols. The bow tie architecture is one of several different structures and functioning principles that
living matter In biology, tissue is a biological organizational level between cells and a complete organ. A tissue is an ensemble of similar cells and their extracellular matrix from the same origin that together carry out a specific function. Organs are th ...
employs to achieve
self-organization Self-organization, also called spontaneous order in the social sciences, is a process where some form of overall order arises from local interactions between parts of an initially disordered system. The process can be spontaneous when suff ...
and efficient exploitation of available resources.{{cite journal , vauthors = Tieri P, Grignolio A, Zaikin A, Mishto M, Remondini D, Castellani GC, Franceschi C , title = Network, degeneracy and bow tie integrating paradigms and architectures to grasp the complexity of the immune system , journal = Theor Biol Med Model , volume = 7 , pages = 32 , year = 2010 , pmid = 20701759 , doi = 10.1186/1742-4682-7-32 , pmc = 2927512


References

Self-organization