Draft:Metabolic Scaling Theory

The Metabolic Scaling Theory (MST) is a set of ideas and models that aim to explain the relationship between the metabolic rate of organisms and their body size. . Central to the theory is Kleiber's Law and the idea that many biological phenomena, ranging from individual physiology to the dynamics of ecosystems, scale with body size in predictable ways.

Metabolic Scaling Theory
Scaling relationships are observed at multiple levels of biology. Metabolic Scaling Theory (MST), which integrates the West, Brown, and Enquist network model (WBE) and the ecological and evolutionary extensions, the metabolic theory of ecology (MTE) , other existing network theories, and empirical knowledge, offers a unified framework to connect scaling phenomena mechanistically. In summary, MST is a set of related theoretical applications of the scaling of metabolism that describe the relationships between the metabolic rate, body size, and temperature in biological systems, ranging from the cellular to the ecosystem level. The theory posits that metabolic rate scales with an organism's body mass to the 3/4 power. This relationship is thought to be a consequence of the fractal nature of resource distribution networks within organisms and the energetic and material constraints on biological processes

Metabolic Scaling Theory explains how metabolic rate, the rate at which organisms consume energy, is influenced by body size and temperature. It is a fundamental aspect of comparative physiology and has important implications for ecology and evolution. The original assumptions and predictions of MST focus on the Allometric scaling (allometry) of organism metabolic rate with organism body size were given by West, Brown, and Enquist (the WBE model), and for how the calling of cellular and organismal metabolism ramifies to ecology were given by the metabolic theory of ecology.

Historical Background
The concept of scaling in biology has a long history, with early observations by Max Rubner, Max Kleiber, and Julian Huxley. However, the modern synthesis of Metabolic Scaling Theory is attributed to the work of West, Brown, and Enquist at the Santa Fe Institute in the late 1990s

West, Brown, and Enquist (1997)
The primary contribution to MST was made by Geoffrey West, James Brown, and Brian Enquist in their 1997 paper. Their work introduced the concept that metabolic rate (B) of organisms scales with their body mass (M) according to the power-law relationship:


 * $$B \propto M^{3/4}$$

Summary and Explanation
The Metabolic Scaling Theory relies on the idea that many physical and biological constraints organisms face result from their size. It is not just metabolic rate that scales with size but many other biological processes and properties.

Extensions and Further Developments
Since the introduction of the basic tenets of MST by West, Brown, and Enquist, several extensions and refinements have been proposed:
 * 1) Temperature Dependence
 * 2) Variability in Scaling Exponents
 * 3) Application to Ecosystems
 * 4) Modifications to Network Models

Conclusion
Metabolic Scaling Theory has provided a framework for understanding the interplay between metabolism, body size, and other biological processes. The WBE model provides the basis to “ scale up ” from individual plants and their specific traits to populations, communities, and ecosystems. The metabolic theory of ecology or MTE extends the WBE model to ecology by invoking four additional principles or assumptions. Intriguingly, these assumptions appear to have identified important organizational principles that are shared across ecological systems.