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Member (Idle past 1700 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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Author | Topic: Definition of Species | |||||||||||||||||||||||||||||||||||||||
Taq Member Posts: 10346 Joined: Member Rating: 6.3 |
Everything that happens within a cell is highly organized and incredibly precise. Cells take in materials, synthesize proteins and other compounds, expel waste and produce energy in precisely the amounts needed. Out of hundreds of theoretically possible amino acids that could exist, only 20 are used for building proteins. And these are arranged in exactly the correct order and in exactly the proper quantities for sustaining the organism. E.coli bacterium have 600 to 800 proteins active at any one time and complex multi-cellular organisms have several thousands. Each protein has a specific function and is specifically suited for that function. Cells have an elaborate system of communication that allows substances to move throughout the organism precisely where they are needed. Can you support any of these claims with any evidence? If what you claim is true then there shouldn't be disease or aging. There wouldn't be any birth defects. Also, if proteins are specified as you claim then you should really tell the people at the HapMap program (http://www.hapmap.org). They are mapping genetic variation in humans and guess what? A lot of that variation includes proteins that differ at the amino acid level.
Then from that knowledge and observation (or despite it), we introduce the mechanism for adaptation as a random, undirected process. Evolution is not undirected. Evolution is directed by selection. If evolution were truly random then detrimental mutations would be passed on at the same rate as neutral or beneficial mutations. This is not what we see.
They don’t change for just no reason, otherwise there wouldn’t so much stasis in the fossil record. Coleanthus is a simple example. Why didn’t this species change over millions of years? It didn’t need to. The rate of mutation in the coelacanth lineage is roughly the same for all other lineages. The difference here is that mutations which didn't change morphology were selected for.
The problem with supposing a mechanism that is not random is that you can’t go very far with it before you are forced to conclude that some intelligence designed it. How so?
Again, what I am suggesting is that perhaps, the mechanism for change is not random and undirected, but in fact, controlled by the cell. The cells genetic structure has certain built in adaptation mechanisms that allow the organism to change in response to its environment. That such mechanisms exist is a fact. Regulation of Bacterial Metabolism You are confusing phenotype plasticity with evolution. Gene regulation can not explain how a bacteria that lacks an enzyme for metabolizing a specific sugar can acquire this enzyme through changing it's DNA sequence. Gene regulation does not involve a change in DNA sequence.
How can we observe and acknowledge the above and then conclude that the mechanism the brought all that about is random and undirected? Because that is exactly what we observe. For example, the Lederbergs were able to show that the mutations which confer antibiotic resistance in bacteria occur in the absence of bacteria (source). Luria and Delbruck were able to demonstrate that mutations which confer phage resistance occurs in the absence of phage (source). Both of these experiments demonstrate that there is no link between the processes which produce mutations and the needs of the organism. IOW, these experiments demonstrate that mutations are random with respect to fitness. So why do biologists claim that mutations are random? Because that is what they observe.
This is an argument of improbability, . . . No, it is an argument from incredulity which is a logical fallacy. If it was about probability you would have done the math for us. You haven't. Instead, you express how you can't believe it. That is incredulity, not improbability.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3 |
Just a few more examples:
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Taq Member Posts: 10346 Joined: Member Rating: 6.3 |
Definition of species is an interesting debate. Please allow this article to help you follow your point to fruition? This is a very, very good point. It is entirely possible to have two separate species that share all of the same genes where the differences between the species are due to differential expression of genes. Also, morphological differences can arise due to the relative differences in mRNA levels for a given gene, and when those genes are turned on during embryonic development and maturation. This is why the cutting edge of evolutionary research (at least in metazoans) focuses so strongly on Evo-Devo.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3 |
Maybe WK or one of the other biologists here could elaborate on this point.
WK did a wonderful job of describing what a frameshift mutation is. I will only add this illustration:
The result of the frameshift mutation in the human myosin gene was a dysfunctional protein due to the massive difference in amino acid sequence caused by the addition (or deletion) of DNA. The result was a weaker jaw muscle. A weaker jaw muscle requires less bone as an anchor. Less bone needed to anchor the jaw muscle allows for a larger cranium, and hence a larger brain. As a counterexample, take a look at this gorilla skull. Notice the massive crests necessary for anchoring the large jaw muscles.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3 |
The few examples of frameshift mutations that I have come across in humans often have terrible consequences Except the one that allowed for one of the most important evolutionary changes in the hominid lineage, the MYH frameshift mutation that allowed for the expansion of the brain.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3 |
I say that every aspect of Darwin's notions of species is already contained in Genesis, and more comprehensively and scientifically posited. Darwin was fighting the idea that Genesis posited a fixation of species. Darwin was suggesting that species were mutable, and that all animals from different kinds shared a common ancestor contrary to what Genesis claims. Also, the definition of species has changed since Darwin's time. With the advent of the Modern Synthesis in the 1930's we now describe speciation with respect to genetic flow instead of Linnaean groupings.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3
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I think what creationsts see re Darwins finches, are still finches with different beaks. They are still different species of finch, are they not? How do you get separate populations of finches with species specific features? How is Genesis useful for understanding genetic flow, lineage specific mutations, and natural selection? Where can I read peer reviewed papers on the mechanism of speciation that is based on Genesis?
I also see that your cladistics get confusing and is in dispute around birds and lizards and mammals, with birds and mammals both being warm blooded, which of course Lizards are not. How does this help us define what a species is? If you want to discuss cladistics and how it is done I would be happy to discuss it in another thread.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3
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This creationist sees rapid diversity as a option within biblical boundaries.
We are more interested in what you can evidence, not what you can see.
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Taq Member Posts: 10346 Joined: Member Rating: 6.3
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What all of these definitions are trying to get at is the underlying genetic mechanisms, those of inheritance and divergence. Even for asexual species you are still talking about a population that is constantly competing leading to cycles of founders and flushes as rare beneficial mutations appear in the population. With sexual species we try to adjust our definitions to reflect gene flow.
When we say that two living populations are separate species what we are trying to relate is the idea that both species were once one species. Through whatever means, that ancestral population split and the two halves began building up differences as mutations accumulated through time. For fossil species we have are looking at the process in action. We can not directly look at the genotype, but we can look downstream of the genotype which is the phenotype. We can see how each branch started accumulating different mutations (or different selective pressures) as evidenced by a difference in morphology. At the foundation of the species definition is inheritance, and the mechanisms of genetics. The results of these simple mechanisms can be quite complex which makes a one-size-fits-all definition of species nearly impossible.
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