This MedLibrary.org supplementary page on Allometry is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
Allometry is the study of the relationship between size and shape,[1], first outlined by Julian Huxley in 1932.[2] Allometry is a well-known study, particularly in statistical shape analysis for its theoretical developments, as well as in biology for practical applications to the differential growth rates of the parts of a living organism's body. One application is in the study of various insect species (e.g., the Hercules Beetle), where a small change in overall body size can lead to an enormous and disproportionate increase in the dimensions of appendages such as legs, antennae, or horns.
Allometry studies shape differences in terms of ratios of the objects' dimensions. Two objects of different size but common shape will have their dimensions in the same ratio. Take, for example, a biological object that grows as it matures. Its size changes with age but the shapes are similar.
Contents |
Allometric scaling
 |
This section is in need of attention from an expert on the subject. Please help recruit one or improve this article yourself. See the talk page for details. Please consider using {{Expert-subject}} to associate this request with a WikiProject |
Allometric scaling's key equation for all of life equates Metabolic Rate P, to body mass W, raised to a power (4μ - 1)/4μ, where μ is percentage of capture by mass W of energy from oxidation reactions, for storage or expenditure. The equation models the rate at which electrical power needs to be captured, given the limitations of organic chemistry, by a biological system, in order to sustain itself for a duration. With metabolic rate expressed in calories/second, or watts, an extremely high metabolic rate, like that seen for masses less than one milligram at μ less than 15%, translates to many seconds, and long life for cells if the energy is available.
This scaling equation, when graphed for a range of values from e-13 to e+8 grams, and from -22 to 141% metabolic efficiency μ, clearly models the evolution of life to the extent that it was driven by metabolic considerations, that is, terms of bioenergetics. This model clearly depicts how energy fluctuations were equilibrated by biological systems in such a way as to drive evolution. This model explains the difference between cancerous cells and stem cells in terms of proliferation and metabolic efficiency, how the former can be triggered to apoptosis, and the proliferation of the latter can be extended, through the application of electrochemistry acting upon μ.
This equation models the mass increase of fat cells, and illustrates, in terms of metabolism and bioenergetics, how fat cells are related to the evolution of mammals by making prolonged in utero development possible. This equation clearly depicts why resort to dieting to reduce fat cell mass is a bad strategy, why increased activity levels is a good strategy, and how to increase muscle mass independently of muscle use.
This equation is not well understood even by its major proponents who, on the one hand, hint it might hold the secret to the aging process, and, on the other, believe that all metabolism is mass dependent, operates at 1000% μ, is the result of respiration, and is not anaerobic, or electrochemical. These beliefs have no variable in the equation to represent them, and even conflict with its terms. The denominator of μ is expressed in amperes. P is expressed in watts. W is expressed in grams mass, and the numerator of μ is the rate at which anabolic organic reactions are triggered by available amperes. The value for W is a reflection of the size and duration of working of the numerator, appearing as either growth or division.
In contrast, one refers to isometric scaling when growth does not lead to a change in geometry of an organism.
References
- ^ Christopher G. Small (1996). The Statistical Theory of Shape. Springer. ISBN 0387947299. (see page 4)
- ^ Julian S. Huxley (1972). Problems of Relative Growth, 2nd, Dover, New York.
Further reading
- Calder, W. A. 1984. Size, function and life history. Harvard University Press, Cambridge, Mass. 431 pp.
- McMahon, T. A. and J. T. Bonner. 1983. On Size and Life. Scientific American
- Niklas, K. J. 1994. Plant allometry: The scaling of form and process. University of Chicago Press, Chicago. 395 pp.
- Peters, R. H. 1983. The ecological implications of body size. Cambridge University Press, Cambridge. 329 pp.
- Reiss, M. J. 1991. The allometry of growth and reproduction. Cambridge University Press, Cambridge.182 pp.
- Schmidt-Nielsen, K. 1984. Scaling: why is animal size so important? Cambridge University Press, Cambridge. 241 pp.
See also
- Allometric law
- Constructal theory
- Evolutionary physiology
- Metabolic theory of ecology
- Phylogenetic comparative methods
- Power law (also know as a scaling law)
Wikipedia content modification information:
- This page was last modified on 30 May 2008, at 07:20.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Allometry".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.