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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Patterns in nature | 5/5 | https://en.wikipedia.org/wiki/Patterns_in_nature | reference | science, encyclopedia | 2026-05-05T03:40:02.241373+00:00 | kb-cron |
Alan Turing, and later the mathematical biologist James Murray, described a mechanism that spontaneously creates spotted or striped patterns: a reaction–diffusion system. The cells of a young organism have genes that can be switched on by a chemical signal, a morphogen, resulting in the growth of a certain type of structure, say a darkly pigmented patch of skin. If the morphogen is present everywhere, the result is an even pigmentation, as in a black leopard. But if it is unevenly distributed, spots or stripes can result. Turing suggested that there could be feedback control of the production of the morphogen itself. This could cause continuous fluctuations in the amount of morphogen as it diffused around the body. A second mechanism is needed to create standing wave patterns (to result in spots or stripes): an inhibitor chemical that switches off production of the morphogen, and that itself diffuses through the body more quickly than the morphogen, resulting in an activator-inhibitor scheme. The Belousov–Zhabotinsky reaction is a non-biological example of this kind of scheme, a chemical oscillator. Later research has managed to create convincing models of patterns as diverse as zebra stripes, giraffe blotches, jaguar spots (medium-dark patches surrounded by dark broken rings) and ladybird shell patterns (different geometrical layouts of spots and stripes, see illustrations). Richard Prum's activation-inhibition models, developed from Turing's work, use six variables to account for the observed range of nine basic within-feather pigmentation patterns, from the simplest, a central pigment patch, via concentric patches, bars, chevrons, eye spot, pair of central spots, rows of paired spots and an array of dots. More elaborate models simulate complex feather patterns in the guineafowl Numida meleagris in which the individual feathers feature transitions from bars at the base to an array of dots at the far (distal) end. These require an oscillation created by two inhibiting signals, with interactions in both space and time. Patterns can form for other reasons in the vegetated landscape of tiger bush and fir waves. Tiger bush stripes occur on arid slopes where plant growth is limited by rainfall. Each roughly horizontal stripe of vegetation effectively collects the rainwater from the bare zone immediately above it. Fir waves occur in forests on mountain slopes after wind disturbance, during regeneration. When trees fall, the trees that they had sheltered become exposed and are in turn more likely to be damaged, so gaps tend to expand downwind. Meanwhile, on the windward side, young trees grow, protected by the wind shadow of the remaining tall trees. Natural patterns are sometimes formed by animals, as in the Mima mounds of the Northwestern United States and some other areas, which appear to be created over many years by the burrowing activities of pocket gophers, while the so-called fairy circles of Namibia appear to be created by the interaction of competing groups of sand termites, along with competition for water among the desert plants. In permafrost soils with an active upper layer subject to annual freeze and thaw, patterned ground can form, creating circles, nets, ice wedge polygons, steps, and stripes. Thermal contraction causes shrinkage cracks to form; in a thaw, water fills the cracks, expanding to form ice when next frozen, and widening the cracks into wedges. These cracks may join up to form polygons and other shapes. The fissured pattern that develops on vertebrate brains is caused by a physical process of constrained expansion dependent on two geometric parameters: relative tangential cortical expansion and relative thickness of the cortex. Similar patterns of gyri (peaks) and sulci (troughs) have been demonstrated in models of the brain starting from smooth, layered gels, with the patterns caused by compressive mechanical forces resulting from the expansion of the outer layer (representing the cortex) after the addition of a solvent. Numerical models in computer simulations support natural and experimental observations that the surface folding patterns increase in larger brains.
== See also == Developmental biology Emergence Evolutionary history of plants Mathematics and art Morphogenesis Pattern formation Widmanstätten pattern
== References == Footnotes
Citations
=== Bibliography === Pioneering authors
Fibonacci, Leonardo. Liber Abaci, 1202. ———— translated by Sigler, Laurence E. Fibonacci's Liber Abaci. Springer, 2002. Haeckel, Ernst. Kunstformen der Natur (Art Forms in Nature), 1899–1904. Thompson, D'Arcy Wentworth. On Growth and Form. Cambridge, 1917. General books
Adam, John A. Mathematics in Nature: Modeling Patterns in the Natural World. Princeton University Press, 2006. Ball, Philip (2009a). Nature's Patterns: a tapestry in three parts. 1: Shapes. Oxford University Press. Ball, Philip (2009b). Nature's Patterns: a tapestry in three parts. 2: Flow. Oxford University Press. Ball, Philip (2009c). Nature's Patterns: a tapestry in three parts. 3. Branches. Oxford University Press. Ball, Philip (2016). Patterns in Nature: why the natural world looks the way it does. University of Chicago Press. Murphy, Pat and Neill, William. By Nature's Design. Chronicle Books, 1993. Rothenberg, David (2011). Survival of the Beautiful: Art, Science and Evolution. Bloomsbury Press. Gielis, Johan (2017). The Geometrical Beauty of Plants. Atlantis Press. Stevens, Peter S. (1974). Patterns in Nature. Little, Brown & Co. Stewart, Ian (2001). What Shape is a Snowflake? Magical Numbers in Nature. Weidenfeld & Nicolson. Patterns from nature (as art)
Edmaier, Bernard. Patterns of the Earth. Phaidon Press, 2007. Macnab, Maggie. Design by Nature: Using Universal Forms and Principles in Design. New Riders, 2012. Nakamura, Shigeki. Pattern Sourcebook: 250 Patterns Inspired by Nature.. Books 1 and 2. Rockport, 2009. O'Neill, Polly. Surfaces and Textures: A Visual Sourcebook. Black, 2008. Porter, Eliot, and Gleick, James. Nature's Chaos. Viking Penguin, 1990.
== External links == Fibonacci Numbers and the Golden Section Phyllotaxis: an Interactive Site for the Mathematical Study of Plant Pattern Formation