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Author Topic:   Human Evolution - Speciation
wormjitsu
Inactive Member


Message 31 of 39 (160897)
11-18-2004 4:53 AM
Reply to: Message 30 by coffee_addict
11-17-2004 10:13 PM


Do you have a link about Chornobyl?
I'd appreciate that.

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 Message 30 by coffee_addict, posted 11-17-2004 10:13 PM coffee_addict has replied

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coffee_addict
Member (Idle past 467 days)
Posts: 3645
From: Indianapolis, IN
Joined: 03-29-2004


Message 32 of 39 (161079)
11-18-2004 1:07 PM
Reply to: Message 31 by wormjitsu
11-18-2004 4:53 AM


Dude, just google it.

Hate world.
Revenge soon!

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 Message 33 by NosyNed, posted 11-18-2004 1:18 PM coffee_addict has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 33 of 39 (161082)
11-18-2004 1:18 PM
Reply to: Message 32 by coffee_addict
11-18-2004 1:07 PM


Chernobyl
But it helps to spell it right.

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 Message 32 by coffee_addict, posted 11-18-2004 1:07 PM coffee_addict has replied

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coffee_addict
Member (Idle past 467 days)
Posts: 3645
From: Indianapolis, IN
Joined: 03-29-2004


Message 34 of 39 (161185)
11-18-2004 4:07 PM
Reply to: Message 33 by NosyNed
11-18-2004 1:18 PM


Re: Chernobyl
Hahaha. Sorry about that. My only excuse is I don't speak Russian.

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wormjitsu
Inactive Member


Message 35 of 39 (161650)
11-19-2004 9:42 PM


So since I know very little about mutation, I'm curious...can ANY environmental condition [or change in condition] potentially mutate a living organism or is there a certain criteria that governs this?

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 Message 36 by Quetzal, posted 11-20-2004 12:51 PM wormjitsu has replied

  
Quetzal
Member (Idle past 5862 days)
Posts: 3228
Joined: 01-09-2002


Message 36 of 39 (161807)
11-20-2004 12:51 PM
Reply to: Message 35 by wormjitsu
11-19-2004 9:42 PM


I don't have a lot of time for reply at the moment. However, I'd like to take a few sentences to clarify what a mutation is and what can effect/cause them.
Mutuation is simply a change in the DNA of a cell. It can be caused by simple error (the DNA replication process is fairly sloppy, and the cellular repair mechanisms don't always work). In addition, environmental mutagens (certain chemicals, ionizing radiation, etc) can increase the "normal" error rate causing more mutations than can be attributed to copying mistakes. Finally, certain virii, can insert copies of themselves (or at least bits) into the genome of an organism and ride down the generations. Some of the retroviral insertions can cause mutation. There are some other factors, and other not-strictly-mutation things that can change the genome or development process, but the ones I listed are the most common of what are usually called mutation.
Two things to take away:
1. Mutations do not occur in response to environmental stimuli - except in the case of an increase in environmental mutagens. Critters don't change to suit the environment. When an environment changes, either the population already contains variants which can survive in the new condition, or the population goes extinct.
2. Individual organisms don't adapt. Populations adapt over generations (or they don't and disappear). Mutations occurring in individual organisms have no effect on the population as a whole unless the mutation occurs in a germline cell AND the mutation isn't deleterious to the point that it renders the organism unable to reproduce.

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 Message 37 by wormjitsu, posted 11-22-2004 4:14 AM Quetzal has replied

  
wormjitsu
Inactive Member


Message 37 of 39 (162225)
11-22-2004 4:14 AM
Reply to: Message 36 by Quetzal
11-20-2004 12:51 PM


Am I anywhere near correct if I say that the only way to conclusively cause POSITIVE mutations without the risk of negative mutations is through natural selection? I beleive that this notion was brought up earlier with the mention of eugenics.

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 Message 36 by Quetzal, posted 11-20-2004 12:51 PM Quetzal has replied

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Quetzal
Member (Idle past 5862 days)
Posts: 3228
Joined: 01-09-2002


Message 38 of 39 (162632)
11-23-2004 11:18 AM
Reply to: Message 37 by wormjitsu
11-22-2004 4:14 AM


Inre positive mutations: the way you describe it isn't strictly correct. In the first place, the determination of what constitutes "positive" or "negative" mutation is heavily dependent on the environment in which the organism finds itself. What might be a beneficial mutation in one environment may be highly deleterious in another context. Secondly, as I pointed out in my previous response, the environment doesn't cause mutation per se, except in the case where mutagens in the environment may effect the rate of mutation. Variants continuously arise in any population. Natural selection acts on those variants, sort of like a filter. If the variant has a net advantage in the given environment, eventually (all other things being equal and disregarding drift, etc.) ultimately the frequency of that particular variant is likely to increase in the population. By the same token, a disadvantagous variant is likely to either die out or decrease (again, all other things being equal) in frequency, simply because it is less able to compete effectively with the other members of the population.
This is a fairly simplistic explanation, and glosses over quite a bit, but should give you a feel for the subject. Basically, a "positive" mutation gives its posessor some type of advantage. Since the variant that contains this positive mutation (in the particular environmental context) is likely to pass on these positive factors to its progeny AND thus increase the frequency of that variant in the population while natural selection weeds out those with a deleterious mutation, we see the net effect as beneficial. Hope this helps.

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zephyr
Member (Idle past 4540 days)
Posts: 821
From: FOB Taji, Iraq
Joined: 04-22-2003


Message 39 of 39 (162662)
11-23-2004 1:12 PM
Reply to: Message 27 by wormjitsu
11-17-2004 5:06 AM


a few days late,
But I haven't been keeping up too well.
quote:
I wonder, are there any instances wher humans genetically mutated because of intense physical exersion? ei:slavery
I remember seeing this discussion of a gene that affects sprinting performance vs. endurance - the thread's only 4 posts but it's pretty interesting.
EvC Forum: For Peter Borger on the evolution of alpha-actinin-3
It would seem that the development of endurance and the ability to sweat definitely improved our ability to hunt. The mutations wouldn't be a direct result of the exertion of hunting in extreme heat, but would owe their eventual fixation to it.

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