Proving Evolution in the Age of Genetics

The Hovind-ites aren't going to agree. "a dog is still a dog"I guess the exception would be the small male impregnating the large female. I can't really picture the mechanics of it happening (!), but the offspring and parents would most likely surive. I imagine it wouldn't happen in the natural though, so the exception fails.This isn't about Genetics, so I suppose it's off topic. But I don't think Creo's realize it stuff like this that can result in speciation.

You're almost certainly right. Of course, they don't ever seem to be able to make a good operational definition of what the heck they are talking about. This, one begins to sustpect, is deliberate. If they do nail it down they get nailed with their own definition. "Kind" seems to be avoided as a four letter word.

It's difficult to answer, but the chimp DNA matches ours to within 98%Soplar

You should probably clarify what you mean by species, since there are several different definitions that biologists use.The intuitive definition is phenotypic similarity. The problem with this definition is that it isn't too objective.The definition which is most used by biologists is the Biological Species Concept, which states that a species is a reproductively isolated population.There are examples of both of these getting created within the human experience. You must realize, though, that "species" doesn't have a firm foundation within the evolutionary framework, since according to evolutionary theory all life is a branching continuum. This actually gives us insights as to why it is so hard to define "species", since that would be trying to dichotomize a continuum.This message has been edited by JustinCy, 01-13-2005 21:26 AM

The alleles do change, though mutation. To clarify, BTW, alleles don't have genotypes. Individuals have a genotype. What I'm telling you is that there is no quantum leap; horses and donkeys are different species, yet they're not completely genetically incompatible. Only incompatible enough that their interspecific offspring are sterile.There is no quantum leap. There's a continum of speciation, which leads to certain ambiguous situations where we're not sure if we're looking at multiple species or simply subgroups of one species.

I don't think they'd recognize each other as mates. (That's "behavioral reproductive isolation.)

And like any continuum with changes from one end to the other we can frequently be very definite at the extremes and less and less definite as we get closer and closer together in the continuum.That is, there is frequently no difficulty but as two animals get closer to each other the differentiation is harder.Lions and Tigers are, I think all would agree, different species. Then we have the case of the different varieties of dogs. Much less clear.I understand, but don't know enough to say, that there are distinct species that are much more morphologically similar than many dog varieties. None the less they are distinctly different species.mmmm that was a lot of more or less useless blather was it not?I think what needs to be done is have the "creos" make it clear what they mean by "species" or "kind" or any other compartmentalization they want to talk about.

Which, of course, will, in some cases, become different species over time. The blurring of the lines is evolution in action.This message has been edited by NosyNed, 01-13-2005 21:43 AM

except I know dogs that recognize my leg as a mate. haha.Behavioral reproductive isolation. Cool. Thanks.

Except they can be crossed to form ligers (which fans of Napoleon Dynamite know are bred for their skills in magic), which can at least occasionally breed true; or tigons, one of which at least was able to mate with a tiger.They don't mate in the wild because they don't share many habitats, and generally don't recognize each other as mates.So, yeah. Gene flow is possible between them, but negligible in the wild. That, and morphology, is sufficient reason to consider them different species.

All right, my knowledge of genetic terms has wined since I took Molecular Biology has waned, and I don't exactly have the best definition of a species. Nonetheless, I'll try to show this argument.Different species/animals/(whatever term you wish to use) have different DNA. For example, humans have 46, and fruit flies have 8. Now for a fruit fly to eventually evolve into a human, certain changes have to occur in a DNA. To go from a human to a fruit fly, you need to add sets of genes that describe a certain organ/part/(insert your term here). What evidence is there for evolution on the genetic level?

Oh, you're talking about chromosome number. CB141: Differing chromosome numbers

quote:

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Chromosome counts are poor indications of similarity; they can vary widely within a single genus or even a single species. The plant genus Clarkia, for example, has species with chromosome counts of n=5, 6, 7, 8, 9, 12, 14, 17, 18, and 26 [Lewis 1993]. Chromosome counts in the house mouse species (Mus domesticus) range from 2n=22 to 40 [Nachman et al. 1994].

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Chromosomes can split or join with little effect on the genes themselves. One human chromosome, for example, is very similar to two chimpanzee chromosomes laid end-to-end; it likely formed from the joining of two chromosomes [Yunis and Prakash 1982]. Because the genes can still align, a change in chromosome number does not prevent reproduction. Chromosome counts can also change through polyploidy, where the entire genome is duplicated. Polyploidy, in fact, is a common mechanism of speciation in plants.

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DNA doesn't decribe organs. It only describes proteins. It's a common misconception that DNA is a "blueprint", in other words, it contains a kind of encoded diagram or plan of the organism's body. This isn't apparently true. All DNA contains is descriptions of proteins. If we've learned anything from the human genome project, it's that the human genome doesn't contain all that many genes. A lot less than we used to think, in fact.

Well, two humans have "different DNA" in that the genetic sequences aren't the same.You seem to mean that the genetic packaging into chromosomes is the difference.However, this doesn't work. There are many species with the same number of chromosomes that are definitly different species. Therefore there is some other level of difference that you haven't reached yet.Since we have 23 pairs of chromosomes does that mean we are the same species as all other animals that have 23 pairs of chromosomes??

It's impossible at any point: the smallest difference in DNA doesn't result in a change in species or even in variety.This begs the question of what is a species?

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we are limited in our ability to understand
by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}

not a closed loop. the linear progression is there with some more compatable with others near them and less compatable with others further away.certainly size fits into the equation, but you also have reproductive failures (sponaneous abortions and the like) where the mating just doesn't "take" (several examples already given).