Saturday 31 August 2024

Neti neti

Turtle to fish

Not wet mud

Not sea kelp

A

One of the triumphant implications of Maxwell’s theory was an understanding of the nature of light. Rather than a distinct kind of substance, light is a propagating wave in the electric and magnetic fields, also known as electromagnetic radiation. We think of electromagnetism as a “force,” and it is, but Maxwell taught us that fields carrying forces can vibrate, and in the case of electric and magnetic fields those vibrations are what we perceive as light. The quanta of light are particles called photons, so we will sometimes say “photons carry the electromagnetic force.” But at the moment we’re still thinking classically

A
Although a small fraction of nonsynonymous mutations are advantageous or neutral, many are harmful: they impair protein function, often affect physiological or morphological characteristcs, and reduce individuals’ survival or reproduction. For this reason, they tend not to persist in species populations, and so genes evolve more slowly by nonsynonymous mutations than by synonymous substitutions. The genome also has a lot of noncoding DNA, some of which appears to be nonfunctional and which also evolves rapidly, like synonymous mutations, by genetic drift. These differences are important for phylogenetic studies because rapidly evolving parts of the genome provide information on relationships among species that diverged over a short time interval in the recent past. (I mean “short” and “recent” by geological standards, namely hundreds of thousands of years!).

a

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