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Fosdick  Suspended Member (Idle past 5500 days) Posts: 1793 From: Upper Slobovia Joined: |
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Author | Topic: What exactly is natural selection and precisely where does it occur? | |||||||||||||||||||||||
Chiroptera Inactive Member |
quote: Huh? Peahens dig males with long tail feathers. Peacocks with long tail feathers therefore get to breed. Peacocks with short tail feathers don't get dates, and so don't reproduce. How in the world is this not selection? Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: I don't know why you are accusing others of story telling, John. So far all you have ever done is invoke some sort of vague "spirit force" guiding evolution. You have never proposed a mechanism for this "spirit force", not presented any evidence in favor of such a force beyond your own inability to understand natural selection. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
Well, now this is starting to sound like a semantics issue.
Darwin spent a good chunk of Descent of Man discussing sexual selection, and it is clear that he didn't think it was so different from "ordinary" natural selection. I don't think any biologist really thinks of it as any different than natural selection, either. Why do you insist that there is a profound difference between the two? Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: And you are an unpopular story teller. Look, this is very simple. Give us your mechanism for evolutionary change, and then present evidence for your mechanism. Babbling about "spirit forces" and how "sharks and crocodiles would prevent mammalian evolution" just makes you look like a nut. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: By the way, what has Dawkins done in biology? I mean, I know that he is a trained biology, but what was (or is) is field of research? And what impact has Dawkins had on evolutionary biology? All I know about Dawkins is a couple of books he wrote for the mass public. In fact, he is currently the Simonyi Professor for the Public Understanding of Science at Oxford, which sounds like it is more of an educational post than a scientific research one. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
Well, if you don't know the answers to the questions, Hoot, why don't you take a break and let someone else answer them?
Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
Now biologists have an understanding of how Star Trek techo-babble sounds to physicists.
Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: You should probably use the definition of natural selection that everyone else uses (which is pretty much how Percy describes it). The purpose of language is allow communication between people; one aspect of language is the use of words with meanings that people pretty much agree upon. When you start making up your own definitions as you go along, you defeat the whole purpose of communication. -
quote: What the holy hell are you babbling about now? This isn't so hard, Hoot. Populations consist of a number of different individuals. These individuals are different in physical features, some of which are heritable. When some individuals leave more surviving offspring behind than others due to these heritable differences, we call that "natural selection". There are over six billion human beings on this planet. These humans beings are different, often in heritable features. Some human beings have more surviving offspring than others -- when this is due to those heritable differences, then we say that "natural selection" is occurring. You have children. I do not. If that is due to physical, heritable differences between you and I, then we can say that "natural selection" has occurred. There are probably people who have more children than you do. If that is due to physical, heritable differences between you and those other people, then we say that "natural selection" has occurred. This is the meaning of natural selection. This is how natural selection is used by any biologist who is using the term. Sure, you can use natural selection to mean any thing you want it to, but then you are not talking about the same thing everyone else is. Then communication is no longer occurring. By reading your own idiosyncratic meaning onto the phrase when everyone else is using it to mean the standard concept, you are putting yourself in a position where you will not understand what anyone else is saying. By using the phrase to mean your own idiosyncratic meaning, then you are putting yourself into a position where no one else is going to understand what you are saying. If you don't want to communicate with anyone, then you can do that more efficiently by not typing anything at all. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: I suggest that right now. you don't worry about whether it is the individual organism or the gene that is being selected. It isn't important to the definition of natural selection. Try to understand the basic concept first; complications and extensions to the basic concept can come later. I will repeat my earlier attempt at a definition:
Populations consist of a number of different individuals. These individuals are different in physical features, some of which are heritable. When some individuals leave more surviving offspring behind than others due to these heritable differences, we call that "natural selection". Note that I made no mention of whether it is the individual or the gene that is being selected. All I have done is define natural selection in terms of observable phenomena, namely that some individuals leave behind more progeny than others, and that this difference be due to inheritable characteristics. Whether the "individual" is the organism or the gene can be put off later, after it is demonstrated that you understand the basic concept. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
And we can add another:
3. The allele frequencies of population C over time t remain unchanged despite the presence of selective pressure. 4. The allele frequencies of population D over time t change despite the absence of selective pressure and/or random genetic drift. Both of these are possible as well. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: If you say so. But I think you are again demonstrating how little you know about the subject. Edited to add:I still think you should be concentrating on understanding the basic concepts before trying to add complications. Oh, and happy birthday. I hope you have a good one. Edited by Chiroptera, : No reason given. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
As I have been saying, I think it will be more fruitful if we were to focus on the basics first; complications like eusocial species can come later.
I will repeat my attempt at a definition:
Populations consist of a number of different individuals. These individuals are different in physical features, some of which are heritable. When some individuals leave more surviving offspring behind than others due to these heritable differences, we call that "natural selection". First, this definition makes no mention of which is being selected, the organism or the gene. It simply makes a simple observation: some individuals do not reproduce as much as other individuals. Whether the invisible hand of natural selection is actually pointing to the individual that is not reproducing or to its genome isn't yet important. I am merely linking natural selection to the most observable phenomenon. In fact, I suspect that Modulous will basically agree with this definition (although he might, and should, have some reservations about details). Neither he, nor anyone else, has objected to this since I have proposed it twice, so I am assuming that most of us are in broad agreement that it is a useable definition. I would suggest one or two fixes myself, now that I think about it, but let's see what the objections to this definition are first. In particular, I am interesting in seeing what your objections are. As far as I know, this definition is or is close to the actual definition actually used by biologists. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
quote: Sorry for the confusion. Let me try to explain the situations where these things might occur; these are theoretical situations -- whether such a situation can or does occur in reality is a different question.
[qs]4. The allele frequencies of population D over time t change despite the absence of selective pressure and/or random genetic drift.[/quote] This is a situation where there is little or not selective pressures, but mutations continue to occur. Since mutations produce new alleles, the allele frequencies are changing. Some alleles are increasing from 0 to something, and other alleles are decreasing in frequency as new mutations make up more of the genome.
3. The allele frequencies of population C over time t remain unchanged despite the presence of selective pressure. Now this is a situation where a mutation produces a deleterious allele. Natural selection, then, will try to eliminate it. However, if the mutation occurred once, it can occur again; in a large enough population, this same mutation will repeated occur. The production rate is steady as long as the population is steady; however, the elimination rate will depend on the number of individuals with this allele. A basic differential equation problem. At some point, production and elimination will balance each other, and an equilibrium will be reached. It will be eliminated exactly as fast as it is produced, meaning that the allele frequency will hold steady. As I said, a classic differential equations problem. I wonder if some alleles like that producing cystic fibrosis can be explained in this manner? -
quote: I actually don't like the language "individuals selected to reproduce" or "replicators selected to replicate". I don't think it makes sense to speak of "natural selection" occurring to an individual; you can only speak of natural selection when you compare the number of progeny produced by individual A with that of individual B. In fact, accidents do happen, and even very "fit" individuals may just happen to be standing beneath falling branches. What you really need to check is whether, over time, all of the individuals with allele A produce more progeny on average than the individuals with allele B. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
I've been told that I am being confusing, so I am going to bow out of this conversation.
Have fun, though. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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Chiroptera Inactive Member |
I don't think that Hoot Mon was trying to be rude. I think he was just making a friendly joke. At least that is how I read it.
I recognize that the side discussions probably aren't helping much. That is why I am bowing of the thread for a while. People gave their different suggestions as to how to explain the concept; now I think the fewer people are talking, the less potential there will be for confusion. Actually, if their god makes better pancakes, I'm totally switching sides. -- Charley the Australopithecine
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