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Author Topic:   Definition of Species
greyseal
Member (Idle past 2183 days)
Posts: 464
Joined: 08-11-2009


Message 73 of 450 (543986)
01-22-2010 4:01 PM
Reply to: Message 72 by herebedragons
01-22-2010 11:15 AM


Re: Speciation discussion, expectations and reality
How much more change is needed?

Needed for what? To convince me that the ToE is accurate and is the best explanation for life on this planet? To convince me that creation is a myth? Or that God doesn't exist? Or simply to convince me that organisms change over time?

the ToE is not an explanation of abiogenesis, it only explains the diversity of life on this planet. The ToE is correct whether god made everything or whether we all originated in the big bang. Similarly, the existence of god has nothing to do with the ToE.

I am convinced that organisms change over time. It's obvious they do. What I am not convinced of is the extent of change.

good, then you believe in evolution - likely you call it "microevolution". there is no difference between that and "real" evolution, only time. If you feel the earth is not 4.5 billion years but rather <10,000 then we have a problem

One of the major things I am having the hardest time wrapping my mind around is the idea of random mutations being the source for new biological innovations. Let's consider the example of E. coli bacteria developing a new metabolic pathway. Here is my paraphrase of how it happens. E. coli is introduced to an environment with a food source that it normally does not metabolize. During the first several hundred generations, random mutations are occurring until at about 400 generations it hits on one that improves its ability to metabolize the new food source. It can then metabolize the new food source and grow at a normal rate.

Remember, it's not one bacteria, it is a colony of millions, perhaps billions, and they're all evolving at once. The ones that do not metabolyze their food do not do so well and do not reproduce as fast. the ones that metabolyze it better reproduce faster and more. This is an inexorable pressure towards those who can survive, weeding out the ones that can't by - you guessed it - natural selection; they die if they can't survive. If they die, no offspring.

There is no passing on of the secret between bacteria, only from parent to offspring. there is no guided hand there, only blind chance and the ability of life to do what it does.

when the pressure for change is off (i.e. the remainder of the bacteria can metabolyze the new food because the ones that can't are dead) then less will die, meaning that whilst they are STILL evolving, there won't be such a marked change as when this threshold was introduced. no pressure on the colony, no special behaviour and ability being rewarded, no pressure for any other type to arise than what's already there. That doesn't mean they don't try and it doesn't mean they won't, but with less pressure you'll not measure change quite so easily as mass death of those inable to survive can show you.

I picture a "random mutation generator" functioning much like a program they use in movies to decode passwords, trying thousands of combinations until one works. Maybe this isn't very realistic, but still, there would be literally thousands, maybe hundreds of thousands, of mutations that could occur until by chance it stumbles upon the right mutation that works.

you're right, it's bad. there is no mutation like you seem to be indicating, these are not pokemon. There's no flash of light. there's just millions and billions of these mutations happening every second, continuously. with even a slight advantage, parts of the answer will be found very, very quickly. mistakes will be fatal very, very quickly.

The reason they didn't talk about any other sorts of mutations is because, well, how would you check for it?

It's easy to see if a bad food source slows down growth of colonies billions of bacteria in size, but not so easy to see if there's some funky stuff going on that, for example, might solve a disease you have no intentions of testing it against.

They weren't looking for anything else, and it wasn't relevant. You'll have to trust me on that if you can't understand why.

Cheers,

Daniel.


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 Message 72 by herebedragons, posted 01-22-2010 11:15 AM herebedragons has not yet responded

  
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