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Post by tricia on Jan 26, 2014 15:05:22 GMT -5
Sorry, Fred, but you’ve got that a little jumbled. Carbon has an “atomic number” of 6, meaning that there are 6 protons in the nucleus. As in any element, there are normally an equal number of protons and electrons, making each atom electrically neutral. The difference between isotopes is the number of neutrons in the nucleus along with the protons. There exist 3 naturally occurring isotopes of carbon. Carbon-12, with 6 protons and 6 neutrons, makes up about 99% of all carbon atoms on earth. Carbon-13, with 7 neutrons, makes up about 1%. And there is a trace amount of Carbon14, with 8 neutrons at about one part in a trillion. (A bunch of other very short lived isotopes have been produced in reactors.) Carbon-12 and Carbon-13 are stable. Carbon-14 is not. Carbon-14 decays into Nitrogen-14 (7 protons and 7 neutrons) when one if its 8 neutrons turns into a proton by emitting an electron and a neutrino (or is it an antineutrino? or an electron-antineutrino? – can’t remember). During life, living things absorb carbon, including Carbon-14, and living tissue contains Carbon-12, Carbon-13, and Carbon-14 at the naturally occurring ratios. After death carbon is no longer absorbed. Carbon-12 and -13 just sit there, but the amount of Carbon-14 decreases as it decays into Nitrogen, so the ratios change. By measuring the amount of Carbon-14 remaining in a sample, an approximate date of death can be established, up to about 50,000 years (as you said) when there is so little C-14 left that reliable measurements are not possible. Oooooh NOW I get it! lol....why didn't ya say so before?! (I'm totally kidding...I have absolutely no idea what you just said)
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Post by faskew on Jan 26, 2014 18:11:31 GMT -5
Drat! That's what happens when us liberal arts majors start talking about science. I need to get into a ghost-hunter TV show or some such, where my ignorance won't be noticed. 8->
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Post by Deleted on Feb 15, 2014 15:03:56 GMT -5
Hey Tricia, not sure if that's going to help you but I find that the Crash Course youtube series usually does a great job explaining science in fairly simple terms.
Here's a clip on natural selection: And here's their clip on the theory proper:
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Post by Roger (over and out) on Feb 19, 2014 0:18:01 GMT -5
I would add, for the record, that while evolution is in general a successful theory, there are phenomena and behaviors that it does not explain. Homosexuality, for example. What possible survival value can a trait have which specifically involves non-reproduction?
Exceptional artistic, mathematical and musical ability also cannot be explained by evolution, since these abilities have no known biological value or practical application to survival.
Biologist Alfred Russel Wallace, who - it is often forgotten - was co-founder with Darwin of the concept of evolution (in fact Wallace was first to come up with the theory), eventually came to the conclusion that, while the process of selective adaptation or survival of the fittest was valid for some human attributes, for others it was not. He pointed out that, since the law of natural selection by its very nature can only act on useful or harmful characteristics, eliminating the latter and promoting the former, it necessarily follows that the traits developed by this process will be present to a greater or lesser degree in all the individuals of a species. "But in those specifically developed faculties of civilised man which we have been considering (mathematical, artistic and musical ability) the case is very different", he wrote. "They exist only in a small proportion of individuals, while the difference of capacity between these favoured individuals and the average of mankind is enormous." He concluded: "These mental powers differ widely from those which are essential to man, and are for the most part common to him and the lower animals, and could not, therefore, have been developed in him by means of the law of natural selection".
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Post by faskew on Feb 19, 2014 10:06:46 GMT -5
I figure that it's the nature of biological randomness, in that genetics is not truly random. Each random trait is build from bits that already exist, more or less, with minor tweaks, and most will be either useless or even harmful enough to prevent a creature from living long enough to reproduce. Nature is extremely wasteful and useless, dead-end traits are likely very common. Spontaneous abortion and birth defects certainly indicate that's the case, at least in human reproduction.
In any breeding population traits will be in a bell curve, with unusual traits at each end and most traits in the large middle lump somewhere. Unusual traits may not have a current purpose, but may be useful if the environment changes. Or they may be a side effect of something useful. For example, wisdom teeth. We don't need them and they can be painful or even deadly. Why do we have them? Apparently because our jaws used to be larger and, for what was a supposedly useful reason, our jaws are now smaller, leaving not enough room for wisdom teeth in most people. So the prime effect of evolution wasn't to make wisdom teeth a nuisance, but they became so as a secondary effect of something that was useful.
Something like that. 8->
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Post by Deleted on Feb 20, 2014 21:38:23 GMT -5
What about, for instance, apple, orange, and peach trees? Do these trees really need these large fruits to survive? Or were they cultivated by humans to develop that way? What came first? Humans or bananas?
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Post by Deleted on Feb 20, 2014 22:01:19 GMT -5
Bananas...the atheist's nightmare.
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Post by raybar on Feb 20, 2014 22:09:30 GMT -5
Kirk Cameron is (ad hominem) an idiot.
Many of our foods have be modified by selective breeding to the point where today's form and its ancestral stock of 10 or 15 thousand years ago hardly resemble each other.
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Post by Deleted on Feb 20, 2014 22:20:05 GMT -5
I thought the video was amusing. So, how come everything else evolves on its own, but not plants?
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Post by Deleted on Feb 20, 2014 23:18:52 GMT -5
Yeah, I know, I know. Just like dogs.
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Post by Deleted on Feb 21, 2014 4:21:58 GMT -5
I would add, for the record, that while evolution is in general a successful theory, there are phenomena and behaviors that it does not explain. Homosexuality, for example. What possible survival value can a trait have which specifically involves non-reproduction? Homosexuality isn't necessarily a genetic trait, so there's no need for evolution to explain anything there. Remember, the theory of evolution applies to genetics, not behavior. I thought the video was amusing. So, how come everything else evolves on its own, but not plants? But plants do evolve on their own. They just generally don't evolve the way we want them to.
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Post by joan on Feb 21, 2014 10:46:22 GMT -5
Kirk Cameron is (ad hominem) an idiot. Many of our foods have be modified by selective breeding to the point where today's form and its ancestral stock of 10 or 15 thousand years ago hardly resemble each other. Truth is not an ad hom.
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Post by faskew on Feb 21, 2014 13:00:49 GMT -5
Lily wrote: >So, how come everything else evolves on its own, but not plants?
Plants evolve, like everything else. But humans have tweaked certain ones to be more useful for us. (Same for animals.) The first corn was tiny - about the size of a finger joint. Humans selected seeds from the larger ears to plant and, over time, ears of corn are now several inches long. ALL our domesticated plants and animals have been genetically modified by human intervention. We still eat a few wild things, like certain fish, but the wild foods are dying out fast. Here on the mainland we have things like catfish farms - ponds stocked with catfish that are harvested for restaurants. I don't know whether you can even buy wild catfish any more. As our rivers dry up or become polluted, the future is catfish farms or no catfish. 8->
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Post by Roger (over and out) on Feb 21, 2014 17:28:53 GMT -5
That's debatable. There is certainly very strong evidence for a genetic basis to homosexuality. But even if there wasn't, this still wouldn't account for the persistence of homosexual traits over millions of years. It doesn't have to have a genetic basis to be sidelined by evolution.
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Post by faskew on Feb 22, 2014 15:09:25 GMT -5
Zak's right on this one. It's not absolutely conclusive, but there is good evidence for a genetic connection to at least some homosexuality. Certainly some homosexual activity is also cultural. The classical Greeks, for example. Men were expected to marry and have children, but they also believed that women were just animals who could talk and true love for men could only be found among those who could discuss politics, philosophy and poetry - other men. And, of course, there are all the prison and sailor stories. Basically, you can choose whether or not to engage in homosexual acts, but you probably can't choose whether or not you're a homosexual. A subtle difference in many cases. 8->
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Post by Deleted on Feb 22, 2014 21:09:02 GMT -5
And not addressed is bi-sexuality. I believe that is the actual biological reality.
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