Primitive snakes

[Removed_2815]

Here's a prime example: the vermiform appendix. There's no selective pressure for or against this vestigial process, yet we still have it. Perhaps if we weren't so medically advanced as a species, then there would be the selective pressure of ruptured appendices causing septicaemia and death in people before reproductive age; however appendicitis is hardly a selective pressure today. Things like this may eventually regress or entirely disappear, but until having an appendix negatively affects a person's genetic fitness, it's regression would simply be due to a serious of random mutations (though I don't think the human race is going to survive much longer, evolutionarily speaking ).
Cheers,
Ryan

[Removed_2815]

Originally posted by spidergecko
IF IT KILLS YOU BEFORE YOU CAN REPRODUCE, YOU LOSE IT.

Though you won't find this one-liner in textbooks, I like this rule since it just about sums it up...
Ryan

[Double J]

Originally posted by spidergecko
IF IT KILLS YOU BEFORE YOU CAN REPRODUCE, YOU LOSE IT.

Short, sweet, and to the point. Bravo!

[JimmyDavid]

WRONG!
If i don't put my muscles into any kind of effort, they will srink and become smaller. Sure, there's no reason for them to develop but there's also no pressure for it to shrink. Still they do.
The rest of the body follows the same principle.

[Removed_2815]

They shrink because of atrophy, this is a physiological response and has absolutely nothing to do with evolution. You haven't changed your genome and your offspring won't have small muscles because of this.
Ryan

[Double J]

Originally posted by JimmyDavid
WRONG!
If i don't put my muscles into any kind of effort, they will srink and become smaller. Sure, there's no reason for them to develop but there's also no pressure for it to shrink. Still they do.
The rest of the body follows the same principle.

Actually, there is pressure to use your muscles. If you never used your muscles, they would not develop, they would go into atrophy, and you could not get up to eat, and you certainly could reproduce. Thus, there certainly is a selective pressure to use them..... you cannot survive if you do not use them. Without muscles, we cannot move, escape from predators, eat, or reproduce. They are necessary for survival, and we, as all vertebrates have them, and will keep them.

[JimmyDavid]

Originally posted by Double J
[B]Actually, there is pressure to use your muscles.

And if you don't use them, will it hurt to have them strong anyway? I can't see what the body gains by getting rid of muscle?! That was my point when i said that NOT USING is pressure enough to lose.
Double J, i think it goes deeper than that. Your genes affect you and you affect your genes (but in a small percentage, that is not visible in a single generation). That's Darwin's theory. If you spend a life-time running around you will develop strong legs, your genetic sistem will adapt to a certain level, and your children will benefict from that and so on. But the changes will only be visible after many generations.
If it was just about passing on what you got, we would still be stuck as the first carbonic creatures that existed because how could you ever become something different? (duh) .
Some people sugest spontaneous mutations to disregard Darwin, but (although it can happen) it's just dumb.

[Removed_2815]

Originally posted by JimmyDavid
i think it goes deeper than that. Your genes affect you and you affect your genes (but in a small percentage, that is not visible in a single generation). That's Darwin's theory. If you spend a life-time running around you will develop strong legs, your genetic sistem will adapt to a certain level, and your children will benefict from that and so on. But the changes will only be visible after many generations.

This is way off base. Yes, your genes affect you, but you definitely do not affect your genes. Darwin would be appalled to have such words put into his mouth...

If you spend a life time running around, then yes, you as the individual would have stronger legs - this is a physiological response. Your "genetic system" certainly will not adapt as this suggests something is changing genetically, which simply is not the case. Your children will not benefit from your strong legs, since in your example, your legs only got strong from running around for a life-time, and not something that developed as a result of a selective pressure.
If strong legs were a selective advantage, then people with strong legs would face a selection pressure in which those that are most genetically fit, in terms of strong legs, will survive. This is survival of the fittest and this is Darwin's theory of natural selection.

Evolution is "simply" based on a serious of random mutations that either confer a selective advantage or disadvantage on the organism and, due to a variety of selective pressures, the trait is either selected for or against (running around for no reason other than to develop strong legs will not skew evolution into producing a humanoid species with overly strong legs; unless your talking about artificial selection).

Cheers,
Ryan

[JimmyDavid]

RMBolton, if that were true, a species would NEVER turn into another species.
Explain to me: if you don't affect your genes, how come we didn't get stuck as the first life forms around?
By the way, How can you tell that for sure? Do you have info on stuff that puzzles even the greatest scientists?

[Removed_2815]

Originally posted by JimmyDavid
If it was just about passing on what you got, we would still be stuck as the first carbonic creatures that existed because how could you ever become something different? (duh) .

It is all about passing on what you've got, because that's all you have. I'm not sure how much you know about biology, but I'm assuming you know about random genetic mutations. If not, this is merely a natural event whereby a mutation in an organism’s genome arises. Without random mutations then, yes, an organism could never become something different. Fortunately, natural mutation is common and frequent (relatively speaking) when you take into account probabilities of transcription error, and relate this over evolutionary time.

Look at certain penicillin-resistant bacteria for example, this is evolution at an accelerated pace. Through a random genetic mutation, some bacteria are able to secrete an enzyme known as penicillinase, which inactivates penicillin by cleaving the amide bond of its beta-lactam ring. You can imagine how these resistant bacteria would flourish since non-resistant bacteria are destroyed by penicillin, leaving only the resistant strain to reproduce.

Originally posted by JimmyDavid
Some people suggest spontaneous mutations to disregard Darwin, but (although it can happen) it's just dumb.

I'm not sure what you mean here. Random mutations are the backbone of Darwin's theory. For there to be natural selection, there has to be variation in the population. Random mutations are the source of this variation.

Ryan

[Removed_2815]

Originally posted by JimmyDavid
RMBolton, if that were true, a species would NEVER turn into another species.
Explain to me: if you don't affect your genes, how come we didn't get stuck as the first life forms around?
By the way, How can you tell that for sure? Do you have info on stuff that puzzles even the greatest scientists?

Random mutations, natural selection, and evolution are how organisms speciate, this is basic biology.
Evolution is taught in grade school, the "greatest scientists" aren't puzzled...
I suggest you pick up "On The Origin of Species" and an introductory text on Biology, read them cover to cover because I think you're missing some background biological knowledge. That's probably your best place to start.

Cheers,
Ryan

[JimmyDavid]

Not quite. Darwin said mutations occur but never that they were reponsible for the history of evolution. Adaptation was! And that's where the chain of thoughts goes apart among scientists. Some blame mutations on everything, others say life is flexible up the genetic level. My friend, nothing is proven and we can only speculate, that's why i posted "i THINK it goes deeper than that" and didn't get arrogant enough to impose the theory i lean to.

It's clear that you go with the mutation theory (i respect that), i go more along genetic flexibility. Maybe in 1000 years, when we know all about genetics, we can tell for sure wether or not genes are flexible. As for now, i go with it because it makes sense to me.

[Removed_2815]

There's only one theory of evolution.
Adaptation is a result of genetic mutation. There is no dichotomy in theories. Adaptation is an alteration or adjustment in an organism in response to its environment, brought about by selective pressures acting on genetic variation. This is based on mutation. I can't say this any clearer than I already have.

Evolution is just a theory (so they say) but the aspects of evolution are based on solid science, there are no theories within theories. Darwin knew that there was something hereditary that was causing the variation in his finches, he just didn't know what (simply because the discovery of DNA and the study of genetics occurred long after his death).

Not sure what you mean by "genetic flexibility" but I think it has something to do with your strong leg example, which is a ludicrously incorrect example. One of the very first things that people are taught when they decide to study biology is that an individual's genome is immutable. The individual cannot physically change his genes by developing strong legs, this is undeniable fact. My children should be born with 5 fingers on each hand even if I decide to cut mine off.

Ryan

[spidergecko]

Using the "strong legs" example, selective pressure would favour those organisms that require strong legs for survival. The organisms with the weakest legs will be removed from the pool sooner than strong legged ones. The strong legged organisms will proliferate. The weakest of these strong legged organisms have a higher probability of getting killed so in time, only the strongest legged organism will survive. The difference between each organism is a small difference in genetic makeup. Recombination ensures that every individual in a species is potentially different than the others. Those genetic mutations either kill new mutants or enforce the gene pool of current individuals.

If you continually chop the tails off of mice as they are born, 1 million years from now the mice will still produce tailed-offspring (assuming no other mutation takes place).

[CamHanna]

Originally posted by JimmyDavid
Darwin said mutations occur but never that they were reponsible for the history of evolution. Adaptation was!

"Adaptation", in this case, refers the population as a whole. A random mutation occurs at the very beginning of an individuals life, long before birth, though admittedly I don’t understand when exactly, presumably in egg or sperm cell; I’m sure Ryan will know. This individual, by virtue of this random mutation, is more genetically fit (better able to survive and reproduce) than the other individuals in the population. Thus the mutated genes are passed on to the offspring and spread throughout the population, until the entire population has this mutation. This POPULATION has now adapted, using the mutation, to react to some selective pressure. This occurs because individuals without the mutation are not as able to survive and reproduce.

Individual physical fitness, while it may affect an individuals chance of survival, is not heritable. If this physically fit individual has some genetic predetermination to be physically fit then the offspring might also have this predetermined fitness. If the physically fit individual is fit only by virtue of excessive exertion then the offspring will also need to exert themselves excessively to become as physically fit as their parent was. This is an individual adaptation; unless each individual in the entire population trains themselves to be physically fit then the population will not change. This is not evolution.

Mutations can occur in a living individual (ie. a tumor) but this is not in response to anything the individual has done (aside from exposing themselves to carcinogens). This mutation also occurs in only one cell and later in that cells daughter cells; it does not affect the entire “genetic system” and is thus not passed on to the offspring.

Cam

Edit: Then/Than corrections.