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Evolution

Posted Apr 27, '13 at 5:46am

partydevil

partydevil

5,097 posts

danm i've been in the hospital for a week and exactly this week, 1 of those guys pop up. and i wasn't able to join in the fun. =(

 

Posted May 24, '13 at 4:03pm

HahiHa

HahiHa

5,031 posts

Knight

Pokemon
Not felling to write

If you don't feel like writing, don't write.

Besides, Pokemon is not the way evolution happens. Evolution is not random but it has no goal, no ultimate stage.

 

Posted May 25, '13 at 10:39am

pangtongshu

pangtongshu

8,569 posts

lol dude I know
I just want to have 100 form posts
At the begining I just put 3 random posts
I can't delete them so I just putting posts and when I come to 100 I'll not post more

And about Pokemon
Just to write something

That's called spamming..and is very looked down upon.
Don't do that.

 

Posted May 25, '13 at 1:06pm

aknerd

aknerd

1,276 posts

*Looks at last couple pages... looks at opening post...*

People LOVE to "debate" evolution. But that's silly, and doesn't really solve anything. If you are in a debate about whether or not evolution is a valid theory, you are either debating someone who has little to no idea what what evolution is, or ARE the person who has little to no idea what evolution is. That doesn't sound like very much fun, so let's not do that, okay?

*cough*

Someone recently mentioned that evolution is not random. I suppose this is a mostly true statement, but, as with all things, its a bit more complicated than that. So, that being said, I propose that the next topic for discussion should be...

NEUTRAL THEORY

There are a few different neutral theories in ecology/evolution, but I know the least about the neutral theory of molecular evolution, so I'd like to start with that as it will increase the odds of me learning something new.

Basically, this theory states that most of the genetic differences we see between species on a molecular level don't have anything to do with fitness. I guess an intuitive explanation would be that the effects of an individual mutation are almost always so small that they really don't come into play on a phenotypic level, especially when you consider that a lot of our genome is just junk code.

So, without relying on the wiki article TOO much, what do ya'lls think about this? What are some implications of neutral theory? This is one of the most contested topics in evolution, so there should be plenty to talk about...

 

Posted May 25, '13 at 3:38pm

HahiHa

HahiHa

5,031 posts

Knight

Someone recently mentioned that evolution is not random. I suppose this is a mostly true statement, but, as with all things, its a bit more complicated than that.

Well it depends what, I'll call it 'step', you're looking at. Every organism experiences a basic rate of random mutations. The point is that if there was no selection or any other factor acting on said difference, each organism of a single species would have the same fitness, leading to a sprawl of randomness. Since this isn't the case, specific characteristics are being selected for, in a non-random matter. Organisms are adapted 'to' something.

So, without relying on the wiki article TOO much, what do ya'lls think about this? What are some implications of neutral theory? This is one of the most contested topics in evolution, so there should be plenty to talk about...

I might read the article later for more infos, but from your short summary, it sounds reasonable. I mean, what is fitness? To put it in a simplistic way, anything related to and influencing your reproduction success will count for your general fitness, and anything that does not, does not.

It is established, as far as I know, that not every feature is, or has ever been, adaptive. An adaptation may be linked with a secondary change that will not affect your fitness, but will change nonetheless.

And as you said, most mutations don't really have any impact. Although this also implies that most mutations will not affect your germ cells and thus will not be transmitted; I don't know if this has any relevance to the theory, but it might impair its relevance.

So basically, I do not disagree that any molecular diversity doesn't necessarily have a fitness impact; I might however challenge the notion that "most of it" is not relevant to fitness. It seems like a bold claim.

 

Posted May 26, '13 at 5:01pm

MageGrayWolf

MageGrayWolf

9,676 posts

Knight

Did some searching on neutral theory.

This had a nice brief run down of it. and pointed out best that

"The neutral theory is easily misinterpreted. It does NOT suggest:

That organisms are not adapted to their environments
That all morphological variation is neutral
That ALL genetic variation is neutral
That natural selection is unimportant in shaping genomes
"

http://evolution.berkeley.edu/evosite/e … eory.shtml

This site had a pretty good overview on the subject.
http://www.blackwellpublishing.com/ridl … heory1.asp

I would suggest reading it over your self, I will just post the summary here.

"The neutral theory of molecular evolution suggests that molecular evolution is mainly due to neutral drift. Alternatively, molecular evolution may be mainly driven by natural selection.

Four main observations were originally interpreted in favor of the neutral theory: molecular evolution has a rapid rate, its rate has a clock-like constancy, it is more rapid in functionally less constrained parts of molecules, and natural populations are highly polymorphic.

Kimura argued that the high rate of evolution, and the high degree of variability of proteins, would, if caused by natural selection, impose a high genetic load. Neutral drift, however, can drive high rates of evolution, and maintain high levels of variability, without imposing a genetic load.

The constant rate of molecular evolution gives rise to a 'molecular clock'.

Neutral drift should drive evolution at a stochastically constant rate; Kimura pointed to the contrast between uneven rates of morphological evolution and the constant rate of molecular evolution and argued that natural selection would not drive molecular evolution at a constant rate.

The molecular clock for proteins ticks over according to absolute time rather than generational time. But for silent changes in DNA, lineages with shorter generation times probably evolve faster. Neutral drift should cause the molecular clock to run according to generational, not absolute, time.

Selection can operate without producing impossible genetic loads, and Kimura's original case for the neutral theory is no longer convincing.

The neutral theory explains the higher evolutionary rate of functionally less constrained regions of proteins by the greater chance that a mutation there will be neutral.

Selectionists explain the higher evolutionary rate of functionally less constrained regions of proteins by the greater chance that a mutation there will be a small, rather than a large, change.

Pseudogenes and silent changes in third codon positions may be relatively functionally unconstrained. These parts of the DNA evolve faster than do the first two positions in codons, and meaningful third base changes. Neutralists attribute this high rate of evolution to enhanced neutral drift.

For amino acids encoded by more than one codon, there are consistent biases in the frequencies of the codons. Changes between the silent codons are therefore not completely unconstrained.

The neutral theory predicts a positive relation between the degree of variability of a molecule and its rate of evolution."

So it would seem the debate is over just how much random drift plays a role in changes at the molecular level.

 

Posted Feb 26, '14 at 4:50am

pangtongshu

pangtongshu

8,569 posts

Continuing a discussion from Theism and Atheism

The whole idea that animals/people can evolve into entirely different animals ignores that a given animal's DNA doesn't hold the genetic information to create anything other than another one of that kind of animal.

An animal doesn't just suddenly become another animal, however. The process is a slow one, working from all the way down to the level of alleles.

Also, no one has yet seen the so called missing link that would give evolution some credit. A few pig bones found in Africa do not provide evidence of a missing link.

Our grand collection of Transitional fossils disagree with you on that point.

 

Posted Feb 26, '14 at 4:56am

themastaplaya

themastaplaya

661 posts

Continuing discussion......

Alright then. The whole idea that animals/people can evolve into entirely different animals ignores that a given animal's DNA doesn't hold the genetic information to create anything other than another one of that kind of animal. Also, no one has yet seen the so called missing link that would give evolution some credit. A few pig bones found in Africa do not provide evidence of a missing link.

Our grand collection of Transitional fossils disagree with you on that point.

Your grand collection of perfectly normal bones that have been lied about and have had entire skeletal displays built around them that were dreamed up.

 

Posted Feb 26, '14 at 5:02am

pangtongshu

pangtongshu

8,569 posts

Your grand collection of perfectly normal bones that have been lied about and have had entire skeletal displays built around them that were dreamed up.

Lied about? Do you have a source on this?

There is no truth to the claim by creationists and others that there are huge gaps (i.e., “missing links”) between ancient apes and humans. If anything, there is an embarrassment of riches " so many specimens have been found in the past decade or two that the only challenge is clearly establishing their positions in the family tree and deciding which are truly in the direct line that leads to modern humans and which are evolutionary dead ends. Claims of “missing links” or “gaps” are only valid in the sense that when one transitional fossil is found, this creates two more “gaps”!
-From a fellow user on AG who shall remain anonymous unless he/she wishes to be known. Whether this is a quote or not from elsewhere is unsure.

 

Posted Feb 26, '14 at 5:22am

themastaplaya

themastaplaya

661 posts

Pang, link to the following if you dare. This will help explain my opinion why evolution is bull----.
(use control C, and control V to link if this doesn't work)
http://www.biology-online.org/biology-forum/about22923.html

 
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