Posted on 08/09/2005 9:09:21 AM PDT by Crackingham
Scientists have discovered one of the most intricate examples of convergent evolution with the help of South American "poison" frogs and ants and their cousins in Madagascar. (And here's an odd fact for smokers: one Madagascan frog studied was found to have nicotine in its system!)
Poison frogs can't make their own poison--they steal it from ants. Poison frogs secrete a variety of chemicals called alkaloids to create a poisonous defense against predators. Since they can't produce alkaloids on their own, these frogs maintain a steady diet of specific alkaloid-rich ants to keep up their defense.
Now, Valerie Clark of Cornell University and her colleagues have detailed two instances of convergent evolution--the process in which organisms not closely related independently acquire similar characteristics while evolving in separate ecosystems--between frogs and ants on two continents.
First, species of ants high in alkaloids had to evolve on two separate continents.
"The ants had to be there with alkaloids for the frogs to evolve to get alkaloids in their skin," Clark told LiveScience.
Then the frogs had to develop a resistance to the alkaloids--instead of spitting out the ants or passing the alkaloids through their systems, the frogs became able to keep their ant dinners down. Then they evolved to make use of the alkaloids themselves.
Also, both the frogs in South America and Madagascar evolved to have "don't-eat-me" skin colorings, the final step in a remarkable tale of multi-step convergent evolution.
Up until now, scientists have mainly studied frogs from South America and Australia. But Clark and her colleagues showed that the Madagascan frogs needed the same types of food to be poisonous.
They examined the stomach contents of 21 frogs from the genus Mantella and found that alkaloid rich ants made up 67 percent of their food intake.
Not only that, but they found nicotine--the same chemical found in cigarettes--in one Mantella baroni frog out of 22 examined. Nicotine is produced by plants and can sometimes be found in animals that eat these plants. But so far no nicotine-producing plants have been found growing in the area where this frog was found. This was the first time researchers observed this phenomena and they are not sure how the chemical enters the frog's system.
"Our team has not yet conducted a survey of possible nicotine containing in the area where the nicotine-frog was found, and none of our team's insect samples yielded nicotine in chemical analyses," Clark said. "However, this is some of the most convincing evidence that plant-insect-frog toxin food chains do exist."
Powers?
Dr. Steve Austin
not to be confused with "a man barely alive, 'we can rebuild him, we can make him better than he was ... better ... stronger ... faster.'"
The half life of 40K is 1.28 billion years. Using it to determine the age of rocks less than a million years old, in which less than one 40K atom in a thousand has decayed, is like using a GPS unit to measure the length of a cockroach. In other words, if you want to be able to claim you've found a six foot cockroach and measured its length scientifically, you can do so, but only the gullible will be taken in.
But I will give Austin this. Most creationists are too lazy to collect their own data, and tendentiously misinterpret other people's. Austin tendentiously misinterprets his own!
Sorry, skr. I didn't read enough to see who is agreeing with who. I was just sticking to my little point about the main article, which was conjecture extrapolted as proof.
I can't believe this thread is still growing.
But I did like the frog pictures. Cool.
If you are up on the K-Ar method, and I think you are, then you could not have missed the point of the work.
I didn't miss the point of the work. He applied to newly formed rock a method that's used to date rock that's hundreds of millions to billions of years old. He found dates between a few hundred thousand years and a few million years old, with anyone who knew the method and knew anything about science would say are indistinguishable from zero. He then tried to pretend they are not indistinguishable from zero.
As I said, a great analogy is using a GPS unit to measure the length of a cockroach. You put the device at the head of the cockroach, and measure the position. You put it at the other end, and measure the position. You subtract the two. You get a distance, which will probably be a few feet. Does this mean you have a giant cockroach? Does it mean GPS doesn't work? No, it means a GPS unit measures positions to an accuracy of a few feet, and therefore is not a real useful way of meauring the length of something that's a couple of inches long.
Likewise, potassium argon dating is a good way of measuring the age of billion year old rock. If you apply it to new rock, you'll get an age which is determined entirely by the random and systematic errors of the method, which are a few million years.
'Scientific creationists' are either stupid, or liars, or both. My own opinion is the latter; Austin surely can't be stupid enough to believe what he claims here.
What is the assumption on the concentration of daughter element in the K-Ar method ?
Hint: Go to the nearest university library and check out Dhalrimple's (sp?) book on K-Ar dating.
That would be G. Brent Dalrymple ?. The guy who wrote "Radiometric dating does work! Some examples and a critique of a failed creationist strategy"?
LOL!
From the link: Thus the large majority of historic lava flows that have been studied either give correct ages, as expected, or have quantities of excess radiogenic 40Ar that would be insignificant in all but the youngest rocks. The 40Ar/39Ar technique, which is now used instead of K-Ar methods for most studies, has the capability of automatically detecting, and in many instances correcting for, the presence of excess 40Ar, should it be present.
Game, set, and match to RWP.
So now its the Ar-Ar method that is preferred ...
(huge sigh) ... OK ... let me catch up ...
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