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Author | Topic: Proving Evolution in the Age of Genetics | |||||||||||||||||||||||||||
Clark Inactive Member |
If the situation you describe is the general case (and I would think it is) then those two varieties are separate species are they not? 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.
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NosyNed Member Posts: 9004 From: Canada Joined: |
The Hovind-ites aren't going to agree. "a dog is still a dog" 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.
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Soplar Inactive Member |
It's difficult to answer, but the chimp DNA matches ours to within 98%
Soplar
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JustinC Member (Idle past 4875 days) Posts: 624 From: Pittsburgh, PA, USA Joined: |
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
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crashfrog Member (Idle past 1498 days) Posts: 19762 From: Silver Spring, MD Joined: |
But the alleles of these dogs don't change (or to clarify, the genotypes of these alleles change, but the alleles don't). The alleles do change, though mutation. To clarify, BTW, alleles don't have genotypes. Individuals have a genotype.
How about the quantum leap where the DNA changes in this way to a different species? 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.
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crashfrog Member (Idle past 1498 days) Posts: 19762 From: Silver Spring, MD Joined: |
I imagine it wouldn't happen in the natural though, so the exception fails. I don't think they'd recognize each other as mates. (That's "behavioral reproductive isolation.)
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NosyNed Member Posts: 9004 From: Canada Joined: |
This actually gives us insights as to why it is so hard to define "species", since that would be trying to dichotomize a continuum. 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.
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NosyNed Member Posts: 9004 From: Canada Joined: |
or simply subgroups of one species. 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
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Clark Inactive Member |
I don't think they'd recognize each other as mates. (That's "behavioral reproductive isolation.) except I know dogs that recognize my leg as a mate. haha. Behavioral reproductive isolation. Cool. Thanks.
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crashfrog Member (Idle past 1498 days) Posts: 19762 From: Silver Spring, MD Joined: |
Lions and Tigers are, I think all would agree, different species. 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.
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commike37 Inactive Member |
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?
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crashfrog Member (Idle past 1498 days) Posts: 19762 From: Silver Spring, MD Joined: |
For example, humans have 46, and fruit flies have 8. Oh, you're talking about chromosome number.
CB141: Differing chromosome numbers quote: 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). 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.
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NosyNed Member Posts: 9004 From: Canada Joined: |
Different species/animals/(whatever term you wish to use) have different DNA. 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??
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RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
What two species have DNA that have the closest relation to each other?
That's impossible to answer at this point; 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? we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
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RAZD Member (Idle past 1436 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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).
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