Insights Scaling Laws and the Speed of Animals - Comments

Thanks for the insight! This is a very interesting topic for me, but I must say I was quite skeptical until I realized this is about TOP speed, more in line with physical limits. I'm fairly certain mobility is advantageous across most forms of beings so It certainly makes sense to me that evolution has pushed towards the limits across all scales.

 

This 1.4m "dominance zone" I guess I would call it keeps nagging at me. I'd be grateful for any elaborations you could offer there... as I'm not able to access the paper.

 

I couldn't help but be reminded of another similar study - the one finding (statistically) constant time of emptying the bladder across five orders of magnitude of animal mass (what the authors dubbed 'the law of urination'):
http://arxiv.org/abs/1310.3737

 

Certainly all animals use the same types of muscle proteins for movement, but bacteria and other motile single-celled organisms use very different types of proteins for motion (for example, actinomyosin contraction in animals is driven by ATP hydrolysis whereas flagella are powered by the movement of protons across a membrane). Of course, the authors' estimate relies solely on considering the mechanical properties of proteins in general, so it seems to not be so dependent on how these proteins generate motion, just on the fact that proteins are generating force.

 

"metabolic rate per unit mass ... 2 kilowatts per kilogram of muscle. The paper doesn’t really explain where this comes from, citing controversy in the literature" Yes. This is controversial, but the argument is usually between a power law with an exponent of 2/3 or 3/4. A fascinating paper (The fourth dimension of life: fractal geometry and allometric scaling of organisms. West GB, Brown JH, Enquist BJ. Science. 1999 Jun 4;284(5420):1677-9) will definitely be interesting to readers of this post.

 

You said, "Above that it breaks down because the lifters generally get fatter without getting much more muscular."; do you have a source on that?

 

I'm slightly confused about the title of this... like I understand most parts but it just seems like you are saying all animals have the same rate at which they can move there own body length. Would just like clarifying on that

 

I'm wondering, is the same true for animals like spiders that don't use the same mechanisms to move as most animals do?

 

Some specific examples across species would help understanding this topic!

 

Nice article! Adrian Bejan talks about this kind of thing in his book Design in Nature. He even extends the reasoning to the evolution of technology, like cars and planes. His idea is that the world is organized by flow. That structures that increase the flow of matter are selected.

This is related to the idea that energy from the sun flows through the surface of the earth (coming in as yellowish light and leaving as infrared), and matter forms cycles (like the water cycle, the carbon cycle, etc.).

 

I wondered, isnt square-cube law only affects acceleration? Maintaining a speed at basic means acceleration has to overcome drag force of water or air. With bigger body, the drag force is higher, but not so high as the mass. With theese assumptions i dont find it strange that speed is rather independent from mass.