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Science And Nature

Why are bigger animals more energy-efficient? A fresh response to a centuries-old biological puzzle

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Credit: Pixabay/CC0 Public Domain

If you feel about “unraveling the mysteries of the universe,” you almost certainly think about physics: astronomers peering through telescopes at distant galaxies, or experimenters smashing particles to smithereens at the Large Hadron Collider.

When biologists make an effort to unravel deep mysteries of life, we too have a tendency to grab physics. But our new research, published in Science, shows physics might not will have the answers to questions of biology.

For years and years scientists have asked why, kilo for kilo, burn less energy and require less food than small ones. How come a little shrew have to consume just as much as 3 x its bodyweight in food every day, while a massive baleen whale will get by on an everyday diet of just 5-30% of its bodyweight in krill?

While previous efforts to describe this relationship have relied on physics and geometry, we believe the true answer is evolutionary. This relationship is what maximizes an animal’s capability to produce offspring.

Just how much do physical constraints shape life?

The initial explanation for the disproportionate relationship between and size was proposed nearly 200 years back.

In 1837, French scientists Pierre Sarrus and Jean-Franois Rameaux argued should scale with surface, instead of body mass or volume. It is because metabolism produces heat, and the quantity of heat an animal can dissipate depends upon its surface.

In the 185 years since Sarrus and Rameaux’s presentation, numerous alternative explanations for the observed scaling of metabolism have already been proposed.

Arguably probably the most famous of the was published by US researchers Geoff West, Jim Brown and Brian Enquist in 1997. They proposed a model describing the physical transport of essential materials through networks of branching tubes, just like the circulatory system.

They argued their model offers “a theoretical, mechanistic basis for understanding the central role of body size in all respects of biology.”

Both of these models are philosophically similar. Like numerous other approaches submit in the last century, they make an effort to explain biological patterns by invoking physical and geometric constraints.

Evolution finds a means

Living organisms cannot defy the laws of physics. Yet evolution has shown to be remarkably proficient at finding methods to overcome physical and geometric constraints.

Inside our new research, we made a decision to see what happened to the partnership between and size if we ignored physical and geometric constraints like these.

So we developed a of how animals use energy over their lifetimes. Inside our model, animals devote energy to growth early within their lives and in adulthood devote increasing levels of energy to reproduction.

We used the model to find out what characteristics of animals bring about the greatest quantity of reproduction over their lifetimesafter all, from an evolutionary viewpoint reproduction may be the main game.

We discovered that the animals which are predicted to be most successful at reproducing are the ones that exhibit exactly the sort of disproportionate scaling of metabolism with size that people see in true to life!

This finding suggests disproportionate metabolic scaling isn’t an inevitable consequence of physical or geometric constraints. Instead, produces this scaling since it is advantageous for lifetime reproduction.

The unexplored wilderness

In the famous words of Russian-American evolutionary biologist Theodosius Dobzhansky, “nothing is practical in biology except in the light of evolution.”

Our discovering that disproportionate scaling of metabolism can arise even without physical constraints suggests we’ve been looking in the incorrect place for explanations.

Physical constraints could be the principal drivers of biological patterns less often than has been thought. The options open to evolution are broader than we appreciate.

Why have we historically been so ready to invoke physical constraints to describe biology? Perhaps because we have been convenient in the safe refuge of seemingly universal physical explanations than in the relatively unexplored biological wilderness of evolutionary explanations.

This short article is republished from The Conversation under an innovative Commons license. Browse the initial article.The Conversation

Citation: Why are bigger animals more energy-efficient? A fresh response to a centuries-old biological puzzle (2022, August 20) retrieved 20 August 2022 from

This document is at the mercy of copyright. Aside from any fair dealing for the intended purpose of private study or research, no part could be reproduced minus the written permission. This content is provided for information purposes only.

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