Mimicry: Evolution explanation?


by Spirit
Tags: evolution, explanation, mimicry
Spirit
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#1
Dec3-05, 07:05 PM
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Hey,
Just wondering: How does evolution explains the process by which some species, spceially from insects, have mimicry tactics for defense?

Thx in advance,

Mimicry: The phenomenon in which some species [the mimic] resembles another species [the model] and gains protection from the resemblace.
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cronxeh
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Dec3-05, 08:46 PM
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I suppose you'd have to give a specific set of examples to be analyzed. I think due to the shared nature of genes and common phylogenies, the same characteristics are shared and propagated. It would be strange if a fungus acted like a nematode - and indeed it doesnt mimic it. So the characteristics you are referring to happen among Insecta, because they are related and have same genes for that behavior within the class.
sameandnot
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Dec3-05, 08:56 PM
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must have something to do with consciousness. at least in a very crude sense.
consciousness of environment --> ability to mimic environment --> ability to consciously affect genes?

Moonbear
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Dec3-05, 09:46 PM
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Mimicry: Evolution explanation?


Mimicry is very interesting. In terms of evolutionary theory, the best way to look at it is in terms of convergent evolution...two different species in which the progression of change in appearance has taken a similar direction although they started out differently.

It would also depend on the type of mimicry. For example, a harmless insect that shares similar coloration with a poisonous insect, which offers it protection from predators, may have come about quite coincidentally. For example, if the poisonous insect has red coloration and birds have learned not to eat it, then another insect happens to have a variant that has red coloration that the birds don't eat either, more individuals in that population with that coloration pass their genes along to the next generation than those with a different color, etc.

For other species, there may be learning involved, but it's not really known for certain. An example would be a type of firefly that can change the pattern it blinks to mimic the pattern other species use to attract mates. When it attracts the other species, it eats them. In this case, it's using the mimicry to attract its prey rather than to avoid predators.
saltydog
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Dec5-05, 09:27 AM
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That's just completely by chance: Random mutations affect color patterns in snake skin for example. Just by chance, the color pattern of a non-poisonous snake resembles the appearance of poisonous snakes. Predators avoid the poisonous snakes, also a selective pressure, you know the ones that didn't died so their lineage died off but I digress. The non-poisonous snakes with this color obtain a survival advantage over their peers who do not share the color pattern. Soon, the phenotype becomes dominant which we observe as the mimic. Same dif with the rest of the animal world, plants too. I say we come up with 9 more.

Here's another: Some catapillars secrete a pheromone that resembles the pheromone of ants in their environment. The predator ants normally would chew up the catapillar for baby ant food. Instead, they just craw all over them and ignore them.

Wait, wait, one more: Some orchids resemble the . . . tail end of some insects. The males insects sense this and proceed to . . . well you know what I mean and in the process pollinate the orchids.

All chance: If you toss enough coins on the floor, one will stand on its edge.
cronxeh
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Dec5-05, 10:26 AM
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The Mustelus canis (smooth dogfish shark) has melanohores that it can contract to adapt to their environment, and change the color of its body from gray to brown, and the color of its bottom from yellowish gray to white.

There are other species like the chameleon that have melanophores and chromatophores, a boolean combination of which allow them to chemically manipulate the reflected light.

I suppose you could calculate just how 'by chance' such occurances are in nature, especially in marine biology where some species deep under water have baits on the end of their tails which also illuminate light to attract prey.
selfAdjoint
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Dec5-05, 05:33 PM
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Quote Quote by sameandnot
must have something to do with consciousness. at least in a very crude sense.
consciousness of environment --> ability to mimic environment --> ability to consciously affect genes?

Conscieousness has nothing to do with it. Superficially evolution often mimics conscious choice, so that even Dawkins is led to speak - not seriously - about "Selfish Genes", but it is random variation and selection all the way. The bug that by purest chance looks more like a predator, a poisonous species or a piece of a tree will survive better and leave more descendents. And generation after generation this mechanism will cause the mimicry to get better and better until it's awesome.
Ouabache
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Dec5-05, 07:48 PM
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A common thread in all of these excellent replies is that biological mimicry: whether by color, pattern, behavior, biochemistry and even sound; are perfect examples of how the forces of evolution behave; by random genetic mutation and positive selection pressure, such that the mimic has a survival advantage.

One thing not mentioned, if the population of the mimic exceeds that of its model (species it is imitating), a negative selection pressure occurs.. Predators will associate that the mimic is eatable ; blinking pattern of fireflies will become associated with danger etc..


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