Mathematical model of animal growth shows life is defined by biology, not physics

Monash University scientists have challenged the conventional wisdom that biological patterns are explained by physical constraints.

In a study published today in Sciencethe researchers present their mathematical model of animal growth which describes how animals devote energy to growth and reproduction as they age and grow.

“Despite the fact that living organisms cannot break the laws of physics, evolution has shown itself to be extraordinarily adept at finding fault lines,” said study lead author Professor Craig White of Monash. University School of Biological Sciences and the Center for Geometric Biology. .

An unexplained problem in biology concerns the non-proportional (allometric) relationship between energy metabolism and size.

“Finding that an animal’s metabolism can be explained without invoking physical constraints means that we have been looking in the wrong places when it comes to finding answers as to why this widespread pattern occurs,” said Professor White. .

“We think that physical constraints don’t drive biology as much as we observe as previously assumed, and that evolution has a wider range of options than previously thought,” he said. declared.

An increase in size, during development or evolution, is usually accompanied by a less than proportional increase in energy needs so that, when compared gram for gram, large animals burn less energy and require less food than small ones.

For instance, small mammals as shrews might need to consume up to three times their weight in food each day, whereas the largest baleen whales eat only 5-30% of their body weight in krill each day.

“Our study goes against the conventional wisdom that biological patterns such as allometric scaling occur due to physical constraints,” Prof White said.

“We have designed a mathematical model of animal growth that describes how animals shift their energy allocation from growth to reproduction as they grow in age and size, and show that lifetime reproduction is maximized when the metabolism scales disproportionately with size,” he said.

“Many models presented since the early 19th century have used physical or geometric constraints to explain this pattern, but ours does not. Simply put, classical theories have held that animals have the metabolism they have because they have to, we find that they have the metabolism that they have. because it’s the best.”

Prof White said the study showed that allometric scaling does not have to be the result of physical or geometric limitations. In place, natural selectionnot physics, favors allometric scaling.