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Author | Topic: Does microevolution logically include macroevolution? | |||||||||||||||||||||||
EZscience Member (Idle past 5154 days) Posts: 961 From: A wheatfield in Kansas Joined: |
RR writes: And you call yourself "EZscience"! Sorry - it's a goal not always realized.
RR writes: After a period of time in isolation, we can label this group a "new species." Actually, the specific criterium is reproductive isolation itself. There is no requirement for passage of time or any overt morphological differences. For example, I know of several situations where new species of insects were recognized solely because a particular parasitoid attacked one, but not the other. Sure enough, a simple crossing experiment showed them to be reproductively isolated moth species, although any taxonmist going by morphology alone could never tell them apart. So reproductive isolation is all that really matters and 'species' is the only taxonomic designation that has a true biological meaning. All the others do not.
RR writes: Why would not all microevolutionary changes necessarily lead to macroevolutionary consequences ? Because a lot of variation may be retained *within* species that doesn't necessarily have anything to do with whether or not speciation occurs. Species can also change genetically over time without splitting into two. This is why the phylogenetic species concept is separate from the biological species concept. Think of it this way. You and I are surely different in various 'microevolutionary' ways. That means that your kids and my kids and their decendents may differ in certain recognizable ways, but it doesn't imply that we will each give rise to a different surviving lineage of humans. Here is another example. We used a lot of DDT from the 1940's to the 1960's and many insects developed resistance to it independently. But the evolution of resistance is rarely without some cost. With DDT off the market, the alleles confering resistance in many species have receded to very low frequencies in insect populations because their alternatives are selectively favored with the pesticide isn't around. So pesticide resistance is a good example of a microevolutionary change that not only would be expected to have little consequence to macroevolutionary change in insects, it is actually reversible within species and can be lost.
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robinrohan Inactive Member |
Actually, the specific criterium is reproductive isolation itself. This seems odd. What if you had some black bears in Oregon and some other black bears of exactly the same type in Vermont and never the twain do meet? Sometime in the past they got separated due to a flood or something. But it wasn't very far in the past. According to this definition they are separate species, I suppose. Everything else you've explained makes perfect sense to me. Just because you have changes due to imperfect replication, this does not mean that such changes are evolutionarily significant. But there was something else I was wondering about: Might an argument be made that mutations must occur, that they are built into the very process of reproduction?
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EZscience Member (Idle past 5154 days) Posts: 961 From: A wheatfield in Kansas Joined: |
Reproductive isolation is defined by genetic incompatibility.
In other words, you make reciprocal crosses of males and females from the two bear populations. If viable offspring are produced, they are still the smae species. If no viable offspring are produced, they are separate species. Interestingly, it seems to take very little gene flow between populations of higher organisms to prevent rep. isolation. RR writes: Might an argument be made that mutations must occur, that they are built into the very process of reproduction? Mutations are certainly a consequence of DNA replication, among other things. No process of chemical replication is without some probability of error, so yes, mutations are virtually inevitable. But keep in mind that only mutations in germ cell lines (eggs and sperm) will have any heritability. The other interesting thing about meiotic reduction of germ cells to the haploid state is that there is this wonderful mechanism of 'crossing over' . Chromasomes essentially lose their parental identity and genes of the mother become recombined with those of the father, and each egg and sperm, although carrying only a single copy of genes, carries an entirely unique arrangement of them. This seems to be an almost 'engineered' opportunity for creating new genetic arrangements. It also ensures that there is independent segregation of alleles - they are not inherited as whole bunch from one parent or the other.
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robinrohan Inactive Member |
Reproductive isolation is defined by genetic incompatibility. This is different from what I've heard before, which is that species are separated by the fact that they don't interbreed, not that they can't. You're saying that the deciding factor is that they can't. So "theoretically" a big dog can mate with a little dog and therefore they are all the same species. As far as the rest of your post, I'm going to have to study it a little while. It has terms I'm not familiar with, like "meiotic reductions of germ cells to the haploid state." Now there's a mouthfull!
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EZscience Member (Idle past 5154 days) Posts: 961 From: A wheatfield in Kansas Joined: |
That is correct.
You have all the key points clear. Meiotic reduction refers to the fact that all our cells have 2 copies of all genes (diploid) but when eggs and sperm are formed, they only get one copy (haploid) so that when they fuse together to form a zygote, the diploid state is restored. In terms of the chromasomes, for humans there are 23, but two copies of each in every cell (= 46), one from the egg the other from the sperm. What I am refering to here is that the copy of a particular chromasome you got from your mom, say no. 23, actually contains a mix of the genes from your maternal grandmother and maternal grandfather. Because of crossing over - the chromasome itself isn't inherited as a unit from either parent. Independent segregation refers to the fact that different alleles (alternative forms of the same gene) segregate independently because of this very mechanism. They have evolutionary destinies independent of one another in terms of the genotype they find themself in in the next generation. This mechanism seems eminently well 'designed' to create new genetic combinations every generation. (Please don't take the 'designed' literally).
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robinrohan Inactive Member |
(Please don't take the 'designed' literally). No, I won't. All this is rather difficult but I will study it.
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robinrohan Inactive Member |
I really would suggest that somebody define first what macro-evolution is. I thought it meant that when a new species appears, this is macro-evolution. And I thought that if there are changes within a species but not enough to make it a new species, then that was microevolution. However, the definition of a species is that it has an isolated gene pool, not that it is different from some other life form in the sense of physical traits. What matters is whether it can get it on with this other group in the sense of producing offspring. If it can't, it is a different species from that other group. But according to easy-science, it's not a matter of whether you produce babies but if you are capable of producing babies. So it all comes down to sex. This message has been edited by robinrohan, 06-15-2005 11:09 PM
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robinrohan Inactive Member |
Thanks. I found it. Message #16. In reference to "People who tell the truth" subtopic below.
This message has been edited by robinrohan, 08-01-2005 05:14 PM
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Jianyi Zhang Inactive Member |
quote:Nothing would stop the change, as such thing never occurs. Current theories of evolution with many mainstream evolutionists are pseudo-scientific claims. Gradual reproductive isolation by geographic isolation, sexual or natural selection are just fairy-tales without any prediction value. Nobody can tell which organism by which mechanism, by how long to become what kind of organism. Hilter, Stalin, MAO had all kinds of "scientific evidences" to support their theries, but they can not provide any cases to falsify them. People seem not learning lessons from history.
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tjsrex Inactive Member |
I don't think anyone posted a definition of what Macro-Evolution is so let me give it a shot. Macro-Evolution is when new information is added to the genome. Micro-Evolution is when already existing information is altered. There are some theories going around about how it might be possible for Macro-Evolution to occur, but they are still in there infant stages( transposons, polyploidy). Dispite what some might say there is no proof of Macro-Evolution, that is to say there is no physical evidence other then the characteristics of animals. Macro-Evolution has never been witnessed in a lab is what I am trying to say.
I don't know in my opinion I just don't have enough faith to believe in evolution. Way to many "random","pointless","small","time consuming" mutations for me. Statistically it is not realistic.
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crashfrog Member (Idle past 1467 days) Posts: 19762 From: Silver Spring, MD Joined: |
Macro-Evolution is when new information is added to the genome. Micro-Evolution is when already existing information is altered. When you alter existing information, by definition you have new information.
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tjsrex Inactive Member |
My definition of Macro-Evolution might have been sort of vague so ill give some examples.
Fish do not come complete with all the genes for legs and the structures needed to use them. In order for them to be born with working legs the proper genes must be in place. Some fish might have short fins, long fins, small fins and so on. But unless it has the Genes for a leg that fin is going to stay a fin.
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tjsrex Inactive Member |
Somewhat yes. Successful macro-evolution requires the addition of NEW information and NEW genes that produce NEW proteins that are found in NEW organs and systems. If I see someone who looks extremely hairy because a mutation altered his information. Im not going to say the mutation added something that wasn't already there. It just altered it....I mean you can say it is new because it is not the same as before....but its not really different.
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crashfrog Member (Idle past 1467 days) Posts: 19762 From: Silver Spring, MD Joined: |
Successful macro-evolution requires the addition of NEW information and NEW genes that produce NEW proteins that are found in NEW organs and systems. Right. And all that stuff comes by slight, successive changes to what was there before.
It just altered it....I mean you can say it is new because it is not the same as before....but its not really different. If it's not the same as it was before then indeed, it is different. What else would "different" mean?
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crashfrog Member (Idle past 1467 days) Posts: 19762 From: Silver Spring, MD Joined: |
Fish do not come complete with all the genes for legs and the structures needed to use them. What do you think you need to use legs? Muscles, bones, a nervous system to control them - fish have all that. What do you think fish would need to use legs that they don'thave, besides legs?
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