Question about evolutionary mechanisms
Discussion
So first of all I hope I’m posting this in the right place, as I understand it they’ve closed P&P and started an area under another name that in all other respects is identical but halfway down the page listing topic areas? Makes sense… 
…You know it does
……If I’ve got it all wrong ignore this post as it’s unlikely to interest you
.Classically most text books say species separate and evolve when living in different environments. But this isn’t strictly true is it? After all what you really get are different variations of the same species. They can still breed etc.
So what evolutionary mechanism causes the genetic information to be scrambled to a point where the number of chromosomes, areas genetic information is stored etc. change?
speedy_thrills said:
So what evolutionary mechanism causes the genetic information to be scrambled to a point where the number of chromosomes, areas genetic information is stored etc. change?
Loads of things can change the genetic information within an organism, and therefore change its genotype (genetic makeup in molecular terms) and possibly phenotype (how that genetic makeup is expressed in real terms - e.g. black or brown hair).During DNA replication and cell division, errors (and therefore mutations) can occur. Similarly, stuff like radiation, viruses and certain chemicals can cause mutation. Most of the time these errors are irrelevant and don't really make any tangible difference to the organism. Besides, organisms are very good at identifying the errors and repairing them before they become permanent and pass on to future cells or generations (kind of like a proofreader).
But every now and again, genetic mutations are passed onto the next generation, where they are seen as a change in phenotype (e.g. mutation may cause bird beaks to become longer, which helps them to catch more worms). Therefore birds with longer beaks catch more food, and so more likely to survive and reproduce (therefore passing on long beaks to future generations). So long-beaks out compete their short-beak brethren (which gradually reduce in numbers and may eventually die out). Thus long beaks slowly become the norm and you've got evolution.
It's pretty late and I'm not sure if that answered you question or how well I explained it, but there you go!
Edit: Crap. Just noticed you're a Biochemistry student and so most of that post was probably like teaching your grandmother to suck eggs.
Edited by wiffmaster on Wednesday 8th April 05:24
speedy_thrills said:
Coq au Vin said:
Time. Lots and lots of time.
That'll change the information on the chromosomes but not the number or arrangent of genetic information however.If, for example, a virus inserts its DNA into a cell's DNA, that will affect the arrangement of genes on that chromosome, and possibly how the chromosome folds as well, which in turn would affect which genes are expressed.
Mutations, copy errors, viruses inserting DNA, all can affect chromosome folding, and gene position. Mostly for the worse, of course. But do it for long enough...
OT but I seem to remember that a large percentage of the human genome is actually made up of viral DNA that has been incorporated over the eons.
Beyond a certain level of difference divergence becomes self reinforcing.
The semi diverged lines could still join up again but the directions they are taking start to become self fullfilling. They start to eat different foods, spend more or less time doing certain things, venture into different environments. After a bit, even though they could still breed back into one species, they just don't interact enough to do so.
Ultimately they stop mating altogether. It is often said that people prefer partners like their mothers or fathers. There is probably a lot in this. From an evolutionary point of view the logic goes "My parents survived, I survived, so choosing a similar mate enhances a surviving lineage".
At that point the species have truly divererged. Even though they still could mate they don't interact and even if they did they wouldn't be interested.
The semi diverged lines could still join up again but the directions they are taking start to become self fullfilling. They start to eat different foods, spend more or less time doing certain things, venture into different environments. After a bit, even though they could still breed back into one species, they just don't interact enough to do so.
Ultimately they stop mating altogether. It is often said that people prefer partners like their mothers or fathers. There is probably a lot in this. From an evolutionary point of view the logic goes "My parents survived, I survived, so choosing a similar mate enhances a surviving lineage".
At that point the species have truly divererged. Even though they still could mate they don't interact and even if they did they wouldn't be interested.
Good to see some scientists in today!
The definition of a species (or it was when I learned it) is that it can interbreed with itself, but not with other species. In other words, if two different animals/plants can't interbreed, they are different species.
Split one species across two different environments and it will gradually evolve into two species - divergent evolution - Darwin's finches etc, and possibly man. If divergence is not that great and they can still interbreed, then you have 'strains' or 'races' instead. Conversely you can put two different species into the same environment and they will gradually converge as they adapt to that environment - convergent evolution.
The definition of a species (or it was when I learned it) is that it can interbreed with itself, but not with other species. In other words, if two different animals/plants can't interbreed, they are different species.
Split one species across two different environments and it will gradually evolve into two species - divergent evolution - Darwin's finches etc, and possibly man. If divergence is not that great and they can still interbreed, then you have 'strains' or 'races' instead. Conversely you can put two different species into the same environment and they will gradually converge as they adapt to that environment - convergent evolution.
Wiffmaster is pretty much spot on I think in terms of how DNA mutates and evolves. Although I think he's forgotten to explain why certain plants have literally hundreds of chromosomes.
I can only add that in terms of evolution it's also worth remembering that Natural Selection happens on a genetic level. All genes are selfish (According to R.Dawkins who does more than bait Christians apparently).
Not wanting to be pedantic but it's also worth bearing in mind that there is more than one definition of "species" but they're not perfect. For example (and if memory serves) a Donkey and a Horse can reproduce to create viable but infertile offspring despite not being the same species.
I can only add that in terms of evolution it's also worth remembering that Natural Selection happens on a genetic level. All genes are selfish (According to R.Dawkins who does more than bait Christians apparently).
Not wanting to be pedantic but it's also worth bearing in mind that there is more than one definition of "species" but they're not perfect. For example (and if memory serves) a Donkey and a Horse can reproduce to create viable but infertile offspring despite not being the same species.
Simpo Two said:
Good to see some scientists in today!
The definition of a species (or it was when I learned it) is that it can interbreed with itself, but not with other species. In other words, if two different animals/plants can't interbreed, they are different species.
Split one species across two different environments and it will gradually evolve into two species - divergent evolution - Darwin's finches etc, and possibly man. If divergence is not that great and they can still interbreed, then you have 'strains' or 'races' instead. Conversely you can put two different species into the same environment and they will gradually converge as they adapt to that environment - convergent evolution.
The Finches Darwin saw were most probably sub-species as, although I'm not an expert, I would assume that as they're still 'Finches' they would still be able to interbreed. The definition of a species (or it was when I learned it) is that it can interbreed with itself, but not with other species. In other words, if two different animals/plants can't interbreed, they are different species.
Split one species across two different environments and it will gradually evolve into two species - divergent evolution - Darwin's finches etc, and possibly man. If divergence is not that great and they can still interbreed, then you have 'strains' or 'races' instead. Conversely you can put two different species into the same environment and they will gradually converge as they adapt to that environment - convergent evolution.
Your definition of Convergent Evolution is slightly incorrect. Convergent evolution is where two seperate species evolve the same (or very similar) traits; an example would be the eye. The species are totally unrelated and may not even be in the same environment; however they both, independently evolve an eye to 'solve' the problem of sensory perception. The way they evolve the trait is likely to be completely different although they essentially do the same thing (the eye has evolved something like 20 different times or more). So Convergent Evolution has got nothing to do with species in the same environment convergeing but more different species evolving similar traits.
Also, species in the same environment will often become more different to eachother as competition increases and they become specialists.
Edited by Dr_Gonzo on Wednesday 8th April 10:11
G_T said:
Not wanting to be pedantic but it's also worth bearing in mind that there is more than one definition of "species" but they're not perfect. For example (and if memory serves) a Donkey and a Horse can reproduce to create viable but infertile offspring despite not being the same species.
Not all mules are infertile, there are some female mules that have had foals.What would be interesting would be to find out if their foals (F2 hybrids?) could mate
.
The Black Flash said:
Mutations, copy errors, viruses inserting DNA, all can affect chromosome folding, and gene position. Mostly for the worse, of course. But do it for long enough...
True but it wouldn't create a situation where the number of chromosomes in a species changes...would it? Just the arrangement.The only one situation I could think of was parthenogenesis in a female human with a chromosomal abnormality (and then mating with her son etc.).
But then I found this and suddenly it seems more obvious. So I take it the unusual chromosomal arrangement can be carried through to the next generation...and we all live happily ever afterwards without parthenogenesis
.speedy_thrills said:
The Black Flash said:
Mutations, copy errors, viruses inserting DNA, all can affect chromosome folding, and gene position. Mostly for the worse, of course. But do it for long enough...
True but it wouldn't create a situation where the number of chromosomes in a species changes...would it? Just the arrangement.Of course in organisms as complex as humans, this is usually a bad thing.
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