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Author Topic:   MACROevolution vs MICROevolution - what is it?
mobioevo
Member (Idle past 4198 days)
Posts: 34
From: Texas
Joined: 12-13-2007


Message 73 of 908 (441287)
12-16-2007 11:39 PM


What is it? Nothing.
When Dobzhansky first introduced the words micro- and macro-evolution to the biologist lexicon, biologists had no idea what made up genetic information. The gene was a very abstract concept that existed in the minds of geneticists, population geneticists, and breeders. They had no idea that genetic information was made up of DNA. They had no idea that the genome was such a complex structure. Today we have a very clear concept of what a gene is, and can detail very minute and major changes in the genome.

So definitions like this,

Taz writes:

The way I understand it, the term microevolution refers to small changes in allele frequency due to mutation and natural selection within a population. Macroevolution refers to a kazillion small changes over long periods of time giving rise to changes significant enough to be noticed.

has no use in modern evolutionary studies. There is no reason to have separate definitions for the same process. The only difference between the two is the length of time. When there is change in genetic information over time, use the term evolution. When a new species is created, use the term speciation.


Replies to this message:
 Message 74 by RAZD, posted 12-17-2007 10:13 PM mobioevo has responded
 Message 76 by Elmer, posted 12-18-2007 2:09 PM mobioevo has responded

    
mobioevo
Member (Idle past 4198 days)
Posts: 34
From: Texas
Joined: 12-13-2007


Message 77 of 908 (441755)
12-18-2007 5:12 PM
Reply to: Message 74 by RAZD
12-17-2007 10:13 PM


Re: What is it?
What I am trying to say is that separating evolution into microevolution and macroevolution is not only unnecessary, but also that it is confusing to creationists and other people not trained in evolutionary studies because the terms use the same evolutionary forces. I know that the terms microevolution and macroevolution are throw around to try to help educate people, but that does more harm than good. It makes it seem like there are two evolutionary forces acting on the organisms at different levels. The only difference between the terms is the time scale, and when a new species arises it is because of evolution and some isolation effect.

quote:
Within a population of breeding organisms the dynamics within the population will be to breed and mix genetic\hereditary traits. In a steady-state ecology this will give selective advantage to the more average phenotypes within the population, the ones that "stayed" in the middle...

I don't know what you mean by average phenotypes, but I think you mean overdominance (heterozygous advantage/superiority). Under certain environmental conditions a heterozygote will have higher fitness than homozygotes and will cause balancing selection. But to assume the entire genome has overdominance within this environment is too much of a simplification. Each allele (assuming alleles have no affect on each other) and will have an independent reaction to the environment. Other ways alleles react within an environment is dominance, complete dominance, incomplete dominance, and underdominance.

quote:
...we have a sudden change from a single population with a common purpose, to two very similar but slightly different populations in competition for food, habitat, protection from predators, etc.

Be careful in your language. I have never met a population or species with a common purpose (even in human populations). Competition between subpopulations will be dependent on the speciation event. If it was sympatric or parapatric speciation under which prezygotic and postzygotic isolation are causing reproductive isolation, then yes they will compete for resources. If the speciation event was due to allopatric or peripatric speciation then they will not compete for resources because the populations have been spatial isolated.

I think you have a valid hypothesis

quote:
As I see it, this means that the biggest impact on natural selection in both those new populations will be for divergence from each other to lessen the competition, lower negative selection back towards the level that existed before speciation.
But for your argument to hold you need to show that competition between individuals in the single population before the speciation event was lower than competition between individuals in the two populations after sympatric or parapatric speciation.

quote:
As I see it, this means that the biggest impact on natural selection in both those new populations will be for divergence from each other to lessen the competition, lower negative selection back towards the level that existed before speciation. I see this as a period of marked, high selection pressure that can result (and has resulted) in extinction for one or more populations. This added selection pressure to diverge did not exist before speciation and is caused directly by speciation.

If I understand your argument correctly since these two species that divided from a single species are now competing for the same resources there will be strong selection pressure to maximize the efficiency of resource use. I do not see how this is any different from positive selection on an advantageous allele that allows for more efficient resource use.

quote:
The issue is that macroevolution - the divergence of related species - occurs after speciation has already occurred.

In my opinion your argument does not clearly seperate microevolution from macroevolution. The way beneficial mutations arise within a species and the positive selection that acts on the beneficial allele to rise in frequency is the same way beneficial alleles increase in frequency when two species are competing for the same resources. The divergence of two related species can evolutionarily occur the same way as two individuals within the same species. In fact that is how speciation events occur the divergence of individuals within a species.


This message is a reply to:
 Message 74 by RAZD, posted 12-17-2007 10:13 PM RAZD has responded

Replies to this message:
 Message 81 by RAZD, posted 12-18-2007 8:55 PM mobioevo has not yet responded

    
mobioevo
Member (Idle past 4198 days)
Posts: 34
From: Texas
Joined: 12-13-2007


Message 78 of 908 (441762)
12-18-2007 5:38 PM
Reply to: Message 76 by Elmer
12-18-2007 2:09 PM


Re: What is it? Nothing.
Elmer writes:

The issue, then, is the question of whether or not macro evolution is simply micro evolution 'writ large', meaning that evolution is a matter of material 'extension' {size}, rather than function [form, design]. Darwinists insist on the former, since for them biological change, evolution, is simply a matter of physical parts growing larger or smaller, randomly, [thanks to genetic mutations], so that the resulting organism is forced to accept these accidental morphological/behavioural changes and adapt their vital functions, (both internal and external behaviours), to suit these unasked for changes, or to perish at the point where they cannot.

I do not understand what you mean when you say "material extention [size]" and when you say "physical part growing larger or smaller." I think you mean this in terms of morphology but I'm not sure. I am sure you are just anthropomorphizing your description to make it clearer, but to be clear organisms are not "forced" to do anything including accepting morphological/behavioral changes due to mutations. Also, after the "changes" (mutations) the organism does not adapt, it is the changes that causes the organism to adapt.

Edited by mobioevo, : No reason given.

Edited by mobioevo, : No reason given.

Edited by mobioevo, : spelling


This message is a reply to:
 Message 76 by Elmer, posted 12-18-2007 2:09 PM Elmer has responded

Replies to this message:
 Message 79 by Elmer, posted 12-18-2007 6:58 PM mobioevo has responded

    
mobioevo
Member (Idle past 4198 days)
Posts: 34
From: Texas
Joined: 12-13-2007


Message 80 of 908 (441798)
12-18-2007 7:20 PM
Reply to: Message 79 by Elmer
12-18-2007 6:58 PM


Re: What is it? Nothing.
This may be off topic and I urge you to start a new thread for better clarification on the topic of genetic determinism.

How does your example on giraffes come into conflict with genetic determinism? A genetic mutation causes a giraffe's neck to grow longer allowing it to eat more leaves from the tall trees and thus get more resources. A genetic changed influenced the long neck.

quote:
we now know that organismic traits are not at all the linearly determined results of inflexible chains of immutable chemical reactions generated by accidental molecular reconfigurations at the 'gene'level.

Please provide a source.

quote:
darwinism depends entirely upon the false notion of genetic determinism. Once it is accepted, [as it has been accepted by real scientists since the genome projects wound up], that the gene does not rule the organism, but is merely the organism's tool, and putting paid to all that 'selfish gene' malarkey, we now know that organismic traits are not at all the linearly determined results of inflexible chains of immutable chemical reactions generated by accidental molecular reconfigurations at the 'gene'level

While there can be epigenetic changes that affect the phenotype but not the gennotype of the organism, the epigenetic effects induce the same mechanism as would be if there was genetic change. Gene regulation is an important part of phenotype expression, but without the gene present that phenotype would not exist. This is why the idea of genetic determinism is still alive.

I currently have a proposed new topic dealing with a paper that talks about epigenetics and genetic determinism, but it has yet to be directed to the Biological Evolution area.


This message is a reply to:
 Message 79 by Elmer, posted 12-18-2007 6:58 PM Elmer has responded

Replies to this message:
 Message 82 by Elmer, posted 12-18-2007 10:30 PM mobioevo has not yet responded

    
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