Because in the embryos of more complex organisms you always first see the same design. This is Ernst Haeckel's theory which he calls "biogenetic law," (and he IS partially wrong: it cannot be considered as a "law") so if I don't explain it enough, research it on google using those terms, as I will not be able to reply until next weekend.one_raven said:How and why?
You mean inherited "accumulated" change(s) at a locus or loci on a chromosome(s) within a population that somewhere along the line eventually does lead to a phenotypic change, or else it is termed "neutral." Without an eventual phenotype change, there is no evolution of any sort.
I don't think we have a difference here. We are both saying that the genotype basis first originates as an "accumulatative" allele mutatation at a loci within a population (and I use the term loci rather than locus because almost all most phenotype traits are changed and are due to more than one locus).CharonZ said:No. I meant accumulation of a given allel in a population. Evolution has a genetic basis, not a phenotypical one. A single base exchange can lead to the same amino acid and thus apparently not lead to a phenotype. But for instance lacking the given t-RNA can lead to further downstream consequences.
Again: evolution is basically defined as the change of allel frequency. Evolution doesn't happen to individuals, but to populations. Furthermore, evolution can lead to a change in phenotypes, but doesn't necessarily do so.
Just in order to clarify things (and pardon me if it is somewhat trivial, but better safe than sorry): allels are variants of a given gene on a given position on the chromosome (locus). Usually by mutation (e.g. an error during duplication) or recombination events (e.g. during meiosis) the base sequence of the allel can be changed, thus leading to a change in the allel. The variations can in theory be as small as a single base exchange. Depending on whether there is an amino acid exchange in the resulting protein there can be a change in the activity of the protein and possibly leading to certain phenotypes (although even a "neutral" mutation could have effects but let's leave it aside for now).Why do the alleles change?
Basically yes. Mostly due to random mutations and of course not globally but always only i a limited amount of cells. Only changes that occur in your gametes are inherited to the next generation.one_raven said:Does your DNA change in the course of a lifetime?
I have heard different accounts, and I have heard that we just don't know yet.
Meaning what? That changes that happen elsewhere are not inherited, rather you inherit what was originally there before the changes?CharonZ said:Only changes that occur in your gametes are inherited to the next generation.
Hapsburg said:Of course evolution happened. The two that said "no" are fucktards to the 99.9th degree.
Wrong! Wrong! Wrong! again. When it comes to Natural Selection, the phenotype enables the organism to better survive and is the ONLY ultimate factor that enables it to survive better than the others in the population. At this point in evolution the genotype means diddly-shit.CharonZ said:Basically yes. Mostly due to random mutations and of course not globally but always only i a limited amount of cells. Only changes that occur in your gametes are inherited to the next generation.
Valich:
There is not need for the accumulation of mutations. And as I said, phenotypes are not a factor (although naturally selection of course only does act against them).
OK.CharonZ said:No, every mutation only affects a single cell (unless the cell doubles, then its daughter cell keeps the mutation too).
So, a mutation in a cell of your hand will have no effect on your sperm cells.
If a single sperm cell mutates, only that cell will be affected.
However if the cells involved in sperm production are affected, all cells derived from them will also harbour mutations.
Specialised cells in the testes that undergo differentiation into sperm cells (called spermatogonia, I think.. am not sure, though).Meaning the testes, or does it go further than that?
Stem cells. They have the capability to become any cell in the body, but that does not mean that every cell in the body was once a stem cell, correct?
And I have been consistently agreeing with you.CharonZ said:No. I meant accumulation of a given allel in a population. Evolution has a genetic basis, not a phenotypical one. A single base exchange can lead to the same amino acid and thus apparently not lead to a phenotype. But for instance lacking the given t-RNA can lead to further downstream consequences.
Again: evolution is basically defined as the change of allel frequency. Evolution doesn't happen to individuals, but to populations. Furthermore, evolution can lead to a change in phenotypes, but doesn't necessarily do so.
Again, resorting to whether you or not anyone else has a BA or PhD is totally irrelevant. So why do you even mention it???You assume I don't have a PhD?CharonZ said:Valich, in case you are not able to read the topic (or follow the conversation for that matter): we are talking about evolution. not natural selection, which, I have to add, as you are obviously not getting it, is only one of the shaping forces of evolution, but not evolution itself.
Really, you are likely the first one getting on my ignore list. Ever.
You neither understand what others post, nor obviously your own posts.
One_rave might have a slightly incorrect view of how evolution works, but at least he tries or at least gives a good impression of trying to understand.
You on the other hand celebrate your ignorance. You to confuse others with random posts which include quotes that have no relavance on the matter (which is ok with me), but you also post your own terribly wrong conclusions and try to sell them as truth (which is not ok with me). For everyone with only a peripheral education it is painfully obvious that you don't comprehend what you post. While I have no problems with people not understanding things or having misconceptions (otherwise I wouldn't be able to teach students.....) I can't stand people that are actively spreading misinformation. You may remain ignorant, that's your choice. But there is no need to involve others.
Didn't you ask yourself why especially the forum members that are professionals on this area (either PhDs or PhD students, from what I gather) turn against you?
While I can't speak for all I do think that it is at least partly because we scientists have generally a very low tolerance against again deliberate misinformation and fraud.