How does evolution actually happen

Here is what actually happens but don't tell your science teacher. He will fail you...

"A certain species exists. Something in their habitat changes, eg, new preadatorial (is that a word?) species (or old species becomes more efficient), competition for food increases, climate change, etc..." resulting in extinction of the entire species or few surviving lessening and weakening the gene pool.

"A community of a certain species has a gene pool. Those organisms which have genes better suited for the change in habitat will be more likely to survive and are often the ones that will produce the new generations as they are the ones that will survive the change. (my understanding of natural selection)" Yet the stuation will change again. Much needed genetic traits to deal with the new environment had been lost by the weakening of the gene pool by earlier hostile conditions."

"there is no gene for new structures and the like." You are right
Please excuse my spelling too... Thanks
"How/why did monkeys loose their tails as they evolved into humans? Did the 'tail' gene just disappear over the years? maybe i can answer this for myself:" If the tail genes (if it works that way) dissappears, the monkey has less genetic codes and has evoled downward.

"I saw a documentary once on the congo i think it was, and a point was raised about the possibility that the first stage of human evolution happened there. They showed footage of monkeys which were at the barrier of a forrest, just beside a open land, clear, without any obstacles. These monkeys would sometimes venture out of the forests and onto these open lands. And then they showed some remarkable footage of the monkeys stading up onto their hind legs, much like a human, straight backs. they were getting up to see further down the land. Perhaps it was from this community, millenia ago that the first step towards homo sapiens were made." That is the theory Dudlyhed but nothing but conjectue supports it.

"Perhaps in that community, as more monkies moved onto the plain, height became a more important trait than having a tail... and so those with more height and less tail were chosen as mates." The key word here is Perhaps...

I could be completely wrong..

"please don't comment on the story, It might be totally incorrect and innaccurate, that was something i saw years ago and I'm not saying thats just how it was." You got the TV STORY correct. That is what is believed.

"I've seen mutation mentioned more than a few times. What exactly is mean by mutation? Do you mean the deformation of DNA?" YES and that leads to death and desesease. "if that is so, can all evolution be soley the result of this? How common is deformed DNA?" Mutaion's have to do deformations thus work against positive change.

I hope someones got the aswer for me, let alone understands my question... there have been more than a few tangents so far...

This thread should have nothing to do with creation, just the theory of evolution. [/B][/QUOTE] OK Dudly but both sides should be discussed.

 

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Re: reply

You say that a slight mutation occurs and this is what, over the years will cause a species to evolove. But if one gene in a gamete were to mutate, wouldn't that make it incompatible with the original complementary gene from the opposite gamete? and wouldn't that mean that the same gene would need the same mutation in the genes of the gamete?

What are the chances of that? I know you can say that it is a possibility, but seriously and realistically speaking, what are the chances of two opposite sex organism of the same species have the same mutation on the the same gene mating with each other?


And Deist27... Your comments seem to be reasonable but saying that a mutaion works against a organism is not intirely accurate. It can but I, without really knowing a great deal about mutation (see above) can see how it could have its advantages.

 

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jee alleles have many mutant forms and life seems to reproduce fine... maybe he mean chromosome duplication?

 

Re: Re: reply

And Deist27... Your comments seem to be reasonable but saying that a mutaion works against a organism is not intirely accurate. It can but I, without really knowing a great deal about mutation (see above) can see how it could have its advantages. [/B][/QUOTE]

Let's say a mutation can sometimes have an advantage, say one in a million is the figure given above. The 999,999 bad mujtations would the one good one to get lost long before a good one comes along.

 

Actually more like 1 out of 1000 or less.

Here a good exampe of a answer to your problem:
http://nmsr.org/nylon.htm

 

Re: Re: reply

The mutations are not slight, they are either there or not, it's the resulting change in the protein that is slight.

Yes.

(BTW I like that serendipitous mis-spelling of evolve (evolove). You should think about changing your sciforums name to that, it has so many implications).

No. You may be confusing the double stranded structure of DNA with an organism being diploid. A gene is double stranded DNA, and the 2 strands, for the most part, need to be complementary. There are two copies of a gene (mostly true but there are exceptions which I can explain if you wish) in diploid organisms (one copy from father, one from mother) and one copy can be very different from the other. Example: the sickle cell gene is caused by a single nucleotide substitution in the hemoglobin gene resulting in an amino acid change in the hemoglobin. When an individual gets a sickle cell hemoglobin gene from one parent and a regular hemoglobin from the other parent (called heterozygous for this gene), the individual gets in increase in resistance to malarial infection, but is otherwise fine. An individual who gets sickle cell hemogobin from both parents (called homozygous for this gene) also gets increased resistance to malarial infection, but also gets decreased hemoglobin ability to carry iron ion (say iron ion 10 times fast) resulting in decreased ability of hemoglobin to carry oxygen, resulting in anemia.

low, but irrelevant for evolution.

 

so, for a two gametes to fuse and become a zygote, as long as there are the same number of chromosomes, its possible?

hmmm...
can any two genes of the same sorta function (whats the name for that?) join up?

 

Re: Re: Re: reply

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I just noticed

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same number of homologous chromosomes

?join up in what way?

 

as in...
wait.. I've confused myself...
Ok.. got it...
we get one half of a trait from one parent, the other half from the other... as long as the two genes (I'm sure there's a term for what I am talking about... dammit. I've forgotten all the terminology, I swear I knew it once...) are of the same type of thingy (!) they will produce some sort of phenotypey thingy...

sorry for the vagueness.. but I hope you can understand where I'm comming from..

 

we get half a trait (allele) from each parent, when both alleles are the same they will produce a phenotype.

yes and no,

if an allele is dominant than a single allele will produce a phenotype.
if an allese is recessive than the phenotype is only visible in the homozygote (both alleles are the same type)

besides dominant and recessive mutations you can also have hypomorphic mutations. The gene is still functional, but at al lower level than normal. Sometimes this gives no phenotype. Sometimes it gives a slightly different phentype. Sometimes it has a radically different phenotype.

and i am probably forgetting something.

 

Thanks! It's all kinda coming back now!

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so... a mutated allele and a non mutated allele can still work to produce the phenotype?
just that the phenotype would not nessecarily be similar in anyway to what would be expected, or may be deformed, or maybe even enhanced?

 

here are some thoughts with in mind that I am talking mainly about developmental biology:

most mutations don't have a phenotype.

a lot of mutations that result in an inactive gene (so the gene's function is completely wiped out) have no phenotype even when 2 copies of the defect allele are present. That is because there is a lot of redundancy built into the system.

As you might realize this doesn't really make it very easy to assess the function of a gene. A lot of genes have more than one function and a lot of genes have redundant functions. Basically it is a mess. Only a few genes will actually produce a clear phenotype.

some genes are so important early on in development that when they are inactivated they result in a premature death of the embryo. But they also have function later on, but you can't see them this way because the embryo never develops this far.

if you seriously mess up development at an early stage you will often see a huge effect later on.

 

to me, mutations seem to be seriously insignificant and I find it hard to believe that all evolution stems from it...

is there more to it?

how can all evolution be due to mutations that may not even make that great a change? or even a positive one?

 

mutations are insignificant as a driving force of evolution, but natural selection isn't. It uses the mutations to change the phenotype of the organism.

If you think it is powerless you should take a look at what is capable if we do the selection ourselves. Look at dogs for instance. They show a huge variety of phenotypes, although they all started with the same genetic material not so long ago. If human selection can do all this in a few 1000 years, why couldn't natural selection accomplish something similar during a longer period.

does that help you?

 

so all the different species of dogs are due to mutations?

 

no, due to selection (which was possible because there was genetic variety)