A great divide in life: front drive vs. rear drive

Turns out the automotive divide between front wheel drive and rear wheel drive is pretty basic to all life on Earth. Animals (and their distant relatives choanoflagellates and fungi) are Opisthokonts, meaning their motile cells have rear-mounted flagella. (In most metazoan animals, the most notable motile cells like this are sperm cells). Most other multicelluar life (plants, multicellular algae) are evolved from protists that had two front-mounted flagella that pulled them along rather than drove them from the back. Who'da thunk? 

Also interesting: animals, almost by definition, make almost all their intercellular structure out of triple helix proteins (collagens), whereas fungi make them out of complex polysaccharides (chitin, also used by insects to make external structural parts), and plants mostly use another polysaccharide, cellulose). Interesting twist: the biosynthesis of collagen apparently requires the presence of a considerable amount of oxygen in the environment to proceed. So animals, which began to evolve on a large scale about 700 million years ago, required a long history of photosynthetic organisms to have "poisoned" the atmosphere with enough oxygen for the reactions they used to literally make themselves out of nutrients to proceed. 

An aside: Young Earth creationists would have to twist themselves into triple helices to explain why Gawd would waste all that time and energy on that, except they mostly ignore such complexities in the contingent history of life in their dumb explanations. Ha ha. 

  

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"The answer" to life, the universe & everything... (No, it's not 42, but it is a dimensionless real number): α (alpha), equal to the strength of the electromagnetic interaction between elementary charged particles:

α = ⁠e²4πε₀ħc ⁠≅ 1/137

where 
e is the elementary charge (~1.602×10⁻¹⁹ C);
h is the Planck constant (~6.626×10⁻³⁴ J⋅Hz⁻¹);
ℏ is the reduced Planck constant, ⁠(h/2π⁠ (~1.055×10⁻³⁴ J⋅s);
c is the speed of light in a vacuum(~300Km⋅s⁻¹);
ε₀ is the electrical permittivity of space (~8.854×10⁻¹² F⋅m⁻¹);
μ₀ is the magnetic permeability of space (~1.2567×10⁻⁶ N⋅A⁻²).
As far as anyone knows, having no reason to suspect otherwise, this is and always has been and always will be true everywhere in the universe, but no one really knows why, if there is a why, this number has the value it does. 

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