The researchers show that so-called "constructal theory" can explain basic characteristics of locomotion for every creature -- how fast they get from one place to another and how rapidly and forcefully they step, flap or paddle in relation to their mass. Constructal theory is a powerful analytical approach to describing movement, or flows, in nature.
They said their findings have important implications for understanding factors that guide evolution by suggesting that many important functional characteristics of animal shape and locomotion are predictable from physics.
The findings, published in the January 2006 issue of "The Journal of Experimental Biology," challenge the notion that fundamental differences between apparently unrelated forms of locomotion exist. The findings also offer an explanation for remarkable universal similarities in animal design that had long puzzled scientists, the researchers said.
"The similarities among animals that are on the surface very different are no coincidence," said Adrian Bejan, J. A. Jones Professor of Mechanical Engineering at Duke's Pratt School. "In fact, animal locomotion is no different than other flows, animate and inanimate: they all develop in space and in time such that they optimize the flow of material." In the case of animal locomotion, this means that animals move such that they travel the greatest distance while expending the least amount of energy, he said.
"From simple physics, based only on gravity, density and mass, you can explain within an order of magnitude many features of flying, swimming and running," added James Marden, professor of biology at Penn Stat
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