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How did the mimetic evolve?


After observing the traits of living things and feeling how they are adapted to their respective environments, many people will question the questions: Who designed this?

Of course, the Creator does not exist, all of which is the credit of evolution - but there is another question that comes one after another: How does the creature know how to evolve without the complex wisdom of human beings?

The answer is that creatures neither know nor need to know. Everything is the result of random mutations and natural selection. The evolution of mimicry is the best example.

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We have just introduced the mimetic phenomenon in nature. There are many examples. For example, this kind of Uropyia meticulodina can be seen in Beijing. Their front wings are wide and flat, but the gradient pattern is like a roll. Leaf or bark - this forced perspective is not uncommon in insect camouflage, so some people marvel: how can a little bug know how light and shadow are, more like the sketch I paint - isn't it smart design? Iron certificate?

On the contrary, camouflage patterns are the easiest to explain with evolution. First and foremost, a fertilized egg divides and differentiates many cells, and the whole process has precise regulation. The most important regulation is the location of the cells, or the relationship with the surrounding cells - such as the previous program. The cells observed at the end of the forelimb will determine which finger to differentiate into based on the gradient of the sound factor.

Secondly, more important: although the genetic mutations in evolution are always very subtle, the effects of these mutations on biological patterns can be very intense.

One of the most famous examples is the British birch scorpion: before the 19th century, all the birch scorpions were grayish white with dark spots, just like the material of birch bark, and later the industrial revolutionary soot dyed many birch bark Black, so in 1848, the black varietal appeared suddenly in the birch scorpion, and within a century it became the absolute mainstream, re-avoiding the sight of natural enemies.

After comparing the DNA sequences, we found that these black birch stalks were inserted into a small repeat of a gene related to wing development by a transposon, and the result was that their entire wings were covered by melanocytes.

We have seen another, more extreme example: the wings of the Heliconius numata have seven possible patterns, corresponding to the seven species of Melinaea, making them in all environments. Can be combined with vigilance - and such a delicate Muhammad mimicry uses only one set of alleles.

It is not difficult to understand the small amount of efficiency of genetic mutations in biological patterns: we have long introduced von Neumann's cellular automaton, which is a number of squares, each square According to the color of other squares around, according to a set of rules, the color changes at the end of each round, and the resulting rich pattern is the output.

For such a system, even if the initial conditions are exactly the same, as long as the color change rules are slightly different, it will produce very different results after several rounds - for example, the current pattern is from a white point in the center of a pure black background, at 8 × The results of 62 rounds were calculated on 62 grids using 64 different cellular automata.

To a large extent, the formation of biological patterns is also a kind of cellular automata: a little mutation of the gene can make the same group of cells differentiate into a variety of patterns, from meaningless patterns to vivid camouflage does not need much Changes, this makes natural selection more efficient.

In the case of Macrocilix in southern China, they are often mimicked into bird droppings: Macrocilix taiwana, which is only a few spots of bird droppings. This species is sometimes divided into adjacent ripples. Hooked Moth, known as the Taiwan Ripple Moth (Sewa taiwana)

The mimicry of the Macrocilix mysticata is more successful, like three bird droppings, while the Macrocilix maia mimics the most like, the pattern on the wings is like a splash of bird droppings, and there is a large piece of What is the uric acid excreted in the feces?

So in the end, we still have to conclude that the biological mimicry has not gone beyond the scope of evolution. Instead, it is the most exemplary case of evolution. The small changes in the genetic level have changed the macroscopic traits, which in turn affects the ability of species to adapt to the environment. Survive.