Buzz
The phenomenon where larger animals consume relatively less energy compared to smaller ones is a puzzling question for biologists.
When envisioning tasks like 'illuminating the mysteries of the universe', people immediately think of distant physics: astronomers observing galaxies through telescopes, or physicists 'experimenting' with fundamental particles in particle accelerators.
As biologists strive to elucidate the deep mysteries of the universe, they also tend to approach it with physics to explain. However, according to a recent study published in the journal Science, sometimes physics - the discipline of the material world - also 'throws in the towel' when it comes to some biological issues.
For centuries, scientists have questioned why, relatively speaking, larger animals burn less energy and require less food than smaller animals. Why does a tiny shrew need to consume three times its body weight daily while a giant whale can be adequately nourished with only 5-30% of its body weight, primarily with plankton?
Relatively speaking, the humble mouse is 'more gluttonous' than even the colossal whale.
Despite previous efforts to explain this 'paradox' relying on physics and geometry, biologists believe the real answer lies in evolution. The key lies in optimizing the reproductive capabilities of organisms.
A perplexing question, physics also struggles
The first attempts to explain the phenomenon of 'mice eat a lot, whales eat little' or more accurately, the disproportionate relationship between body size and metabolic needs, occurred nearly 200 years ago.
In 1827, French scientists Pierre Sarrus and Jean-François Rameaux argued that energy metabolism should be proportional to the surface area of the body rather than the mass or volume. The issue lies in the fact that metabolism generates heat, and the amount of heat that an animal can dissipate into the environment depends on its body surface area.
In the 195 years since Sarrus and Rameaux proposed their solution, many other efforts have been suggested.
African elephants are even more modest eaters, consuming only 4-7% of their body weight per day.
Arguably the most renowned among them is the study by American researchers Geoff West, Jim Brown, and Brian Enquist published in 1997. They propose a model describing the transportation of essential substances through a network of branching tubes, simulating the circulatory system.
They argue that their model provides 'a theoretical, mechanical basis for understanding the central role of body size in all aspects of biology'.
The two solutions are academically similar. Like many other approaches put forth in the past century, they attempt to explain biological models by invoking physical and geometric constraints.
The issue lies in evolution
Living organisms cannot exist despite the laws of physics. However, evolution has proven to be adept at overcoming physical and geometric constraints.
In their recent study, biologists at Monash University decided to see what would happen to the relationship between metabolic rate and size if physical and geometric constraints were disregarded.
They develop a mathematical model indicating that animals allocate most of their energy in the early stages of life for growth and, when matured, most of the energy will be allocated for reproductive maintenance.
They attempt to determine which factor in animal life governs reproductive ability throughout their lives, and find that larger animals, despite conserving energy like the example of whales above, are more successful in reproducing.
In other words, natural selection has done its job and made the seemingly perplexing physical aspects happen. American biologist Theodosius Dobzhansky once famously said: 'Nothing in biology makes sense except in the light of evolution'.
In summary, sometimes biology and life are so miraculous that they create what seems like 'miracles' in the physical world.
Source: The Conversation, Allafrica
