Natural Selection

da_prodigy

Natural selection is regarded one of the two basic mechanisms for organic evolution. However it seems to me that natural selection is not a mechanism at all. It is an effect, not a cause. The fittest will survive and this survival is the selection. The only mechanism is the one which make some organisms fittest: Mutation. The problem is how a random proccess like this always make some favours to organisms. Isn't it a bit odd?

toast

da_prodigy;13499 said:

Natural selection is regarded one of the two basic mechanisms for organic evolution. However it seems to me that natural selection is not a mechanism at all. It is an effect, not a cause. The fittest will survive and this survival is the selection. The only mechanism is the one which make some organisms fittest: Mutation. The problem is how a random proccess like this always make some favours to organisms. Isn't it a bit odd?

It's a cause and effect mechanism. For example, the more time you spend learning, the more knowledge you gain. However, beware that you also lose something in return. In this case, the time you used for learning is lost.

Insatiable

da_prodigy;13499 said:

Natural selection is regarded one of the two basic mechanisms for organic evolution. However it seems to me that natural selection is not a mechanism at all. It is an effect, not a cause. The fittest will survive and this survival is the selection. The only mechanism is the one which make some organisms fittest: Mutation. The problem is how a random proccess like this always make some favours to organisms. Isn't it a bit odd?

I too am a fan of the X-Men, but Mother Nature's sense of humour is often not so comical. What we call "mutations" are actually deviations: Down's syndrome, genetically inherited diseases, or other disabilities etc. A mutation for humans virtually never makes survival favourable--an unfortunate fact, but one we must austerely accept. An ordinary human has a better chance of survival than an invalid.

In terms of the animal kingdom, mutations do not account for better survival; rather, it is simply recessive traits that do. A mutation is more of something that is detrimental to survival.

As for natural selection being an effect, it is not. Rather it is the process we name for the fittest having the greatest likelihood of surviving. The effect is the likelihood of surviving or surviving itself. The cause in this case would be (1) a trait conducive to survival (not a mutation because mutations are not contributive to survival) and (2) some sort of phenomenon that triggers the need to have the recessive trait (i.e. something that makes the trait more useful for survival).

NukeChem

The way I've always seen it defined is that natural selection is the action of the external environment as it affects survivability. Traits that better suit an individual of a species to that environment promote survivability, and it is usually a self-regulating process.

Meh, not a biologist so not going to be terribly nitpicky :P

toast

Insatiable;13513 said:

I too am a fan of the X-Men, but Mother Nature's sense of humour is often not so comical. What we call "mutations" are actually deviations: Down's syndrome, genetically inherited diseases, or other disabilities etc. A mutation for humans virtually never makes survival favourable--an unfortunate fact, but one we must austerely accept. An ordinary human has a better chance of survival than an invalid.

In terms of the animal kingdom, mutations do not account for better survival; rather, it is simply recessive traits that do. A mutation is more of something that is detrimental to survival.

As for natural selection being an effect, it is not. Rather it is the process we name for the fittest having the greatest likelihood of surviving. The effect is the likelihood of surviving or surviving itself. The cause in this case would be (1) a trait conducive to survival (not a mutation because mutations are not contributive to survival) and (2) some sort of phenomenon that triggers the need to have the recessive trait (i.e. something that makes the trait more useful for survival).

just one more thing to add:

Law of physic is the reason why x-men or superman don't exist in our world. :teeth:

Insatiable

toast;13527 said:

just one more thing to add:

Law of physic is the reason why x-men or superman don't exist in our world. :teeth:

True, but Storm usually takes care of all matters concerning physics :wink:

Morro

The problem is how a random proccess like this always make some favours to organisms.

If I am understanding this right, you think mutations are always positive? The vast, vast majority (well in excess of 99%) of mutations are negative. Almost all result in abortion, sometimes before pregnancy is even broadcast to the female, or in a still-birth. Of those that DO survive, almost all are severely deformed, and die very young. Only the vast minority get a mutated trait that turns out to be favored by the environment, and thus selected for in the evolutionary sense.

Rolling those dice each time each organism reproduces, it's not difficult to imagine a vast number of positive mutations, cumulatively resulting in the incredible variation in terran life.

Think about a prokaryotic cell on early earth. They might reproduce five times per day. And if it's a highly abundant organism, like cyanobacteria, say, there might be ten trillion of them, on Earth. That's fifty trillion chances at mutation, every single day. Even if only one tenght of a percent gets a mutation, and only one one-hundredth of a percent of THOSE gets a beneficial mutation, that's still five million beneficial mutations, per day, in a single species. Over billions of years (trillions of days,) this can result in quite a bit of change, indeed.

Natural selection is the mechanism of selecting for a certain mutation. Mutation is not a mechanism of evolution. The mechanisms of evolution are natural selection and genetic drift.