Posted on 01/02/2010 10:57:44 AM PST by Restore
Mutations are the raw material of evolution. Scientists at the Max Planck Institute for Developmental Biology in Tubingen, Germany, and Indiana University in Bloomington have now been able to measure for the first time directly the speed with which new mutations occur in plants. Their findings shed new light on a fundamental evolutionary process. They explain, for example, why resistance to herbicides can appear within just a few years.
"While the long term effects of genome mutations are quite well understood, we did not know how often new mutations arise in the first place," said Detlef Weigel, director at the Max Planck Institute in Germany. It is routine today to compare the genomes of related animal or plant species. Such comparisons, however, ignore mutations that have been lost in the millions of years since two species separated. The teams of Weigel and his colleague Michael Lynch at Indiana University therefore wanted to scrutinize the signature of evolution before selection occurs. To this end, they followed all genetic changes in five lines of the mustard relative Arabidopsis thaliana that occurred during 30 generations. In the genome of the final generation they then searched for differences to the genome of the original ancestor.
The painstakingly detailed comparison of the entire genome revealed that in over the course of only a few years some 20 DNA building blocks, so called base pairs, had been mutated in each of the five lines. "The probability that any letter of the genome changes in a single generation is thus about one in 140 million," explains Michael Lynch.
To put it differently, each seedling has on average one new mutation in each of the two copies of its genome that it inherits from mum and dad. To find these tiny alterations in the 120 million base pair genome of Arabidopsis was akin to finding the proverbial needle in a haystack, says Weigel: "To ferret out where the genome had changed was only possibly because of new methods that allowed us to screen the entire genome with high precision and in very short time." Still, the effort was daunting: To distinguish true new mutations from detection errors, each letter in each genome had to be checked 30 times.
The number of new mutations in each individual plant might appear very small. But if one starts to consider that they occur in the genomes of every member of a species, it becomes clear how fluid the genome is: In a collection of only 60 million Arabidopsis plants, each letter in the genome is changed, on average, once. For an organism that produces thousands of seeds in each generation, 60 million is not such a big number at all.
Apart from the speed of new mutations, the study revealed that not every part of the genome is equally affected. With four different DNA letters, there are six possible changes—but only one of these is responsible for half of all the mutations found. In addition, scientists can now calculate more precisely when species split up. Arabidopsis thaliana and its closest relative, Arabidopsis lyrata, differ in a large number of traits including size and smell of flowers or longevity: Arabidopsis lyrata plants often live for years, while Arabidopsis thaliana plants normally survive only for a few months. Colleagues had previously assumed that only five million years had passed by since the two species went their separate ways. The new data suggest instead that the split occurred already 20 million years ago. Similar arguments might affect estimates of when in prehistory animals and plants were first domesticated.
On a rather positive note, the results of the US-German team show that in sufficiently large populations, every possible mutation in the genome should be present. Thus, breeders should be able to find any simple mutation that has the potential to increase yield or make plants tolerate drought in a better manner. Finding these among all the unchanged siblings remains nevertheless a challenging task. On the other hand, the new findings easily explain why weeds become quickly resistant to herbicides. In a large weed population, a few individuals might have a mutation in just the right place in their genome to help them withstand the herbicide. "This is in particular a problem because herbicides often affect only the function of individual genes or gene products," says Weigel. A solution would be provided by herbicides that simultaneously interfere with the activity of several genes.
Turning to the larger picture, Weigel suggests that changes in the human genome are at least as rapid as in Arabidopsis: "If you apply our findings to humans, then each of us will have on the order of 60 new mutations that were not present in our parents." With more than six billion people on our planet, this implies that on average each letter of the human genome is altered in dozens of fellow citizens. "Everything that is genetically possible is being tested in a very short period," adds Lynch, emphasizing a very different view than perhaps the one we are all most familiar with: that evolution reveals itself only after thousands, if not millions of years.
when did species stop producing their own kind?
>>when did species stop producing their own kind?<<
There is no scientific definition of “kind.” It is an English language interpretation of a concept introduced in the Bible.
when did species stop producing its own species?
Vestigial organs? Science has recently shown that the appendix is currently being used by our bodies. If I remember correctly, it is a repository for “good bacteria” that our intestines use to aid digestion.
It may have also been more utilized in the past, when the world didn’t have food preservation and refrigeration.
And how are male teats vestigial? That would imply that at some time in the past men, or male mammals, had functioning breasts! If that were so, then it would seem to me that we have “devolved”. That is to say, we’ve lost functionality we used to have.
What is more logical is the thought that the only thing that makes men male is the Y chromosome. We have all the code in our male bodies to product female offspring (the X chromosome), and that code gives us teats.
>>when did species stop producing its own species?<<
Many times — if a species creates a being that can’t reproduce with its own species, you have a new one.
>>And how are male teats vestigial? That would imply that at some time in the past men, or male mammals, had functioning breasts! If that were so, then it would seem to me that we have “devolved”. That is to say, we’ve lost functionality we used to have.
What is more logical is the thought that the only thing that makes men male is the Y chromosome. We have all the code in our male bodies to product female offspring (the X chromosome), and that code gives us teats.<<
None of which changes my answer. To “devolve” is a value judgment. To “evolve” means to change. The fact you don’t approve of the change is irrelevant.
So donkeys and zebras are the same species? (google zedonk) A donkey and a zebra can mate and have fertile offspring. Theis is because they are the same “kind”.
So, “kind” isn’t a scientific term. It doesn’t mean that it isn’t a valuable term. Perhaps it SHOULD be a scientific term, but isn’t. Perhaps it would be relatively close to the scientific term “genus”. The Bible says that animals produce after their own “kind”.
And kinds have not stopped producing after their own kind. The dog kind will always produce more dogs, even if they become classified as a different species.
never seen a can produce anything other than a cat. never seen a human produce anything buy a human. so when did that stop?
>>None of which changes my answer. To “devolve” is a value judgment. To “evolve” means to change. The fact you don’t approve of the change is irrelevant.<<
But the answer I was replying to was your statement that vestigial organs are proof of evolution. They are not.
“Evolve” doesn’t mean just to “change” it means “develop gradually, esp. from a simple to a more complex form”. Vestigial organs would be evidence of the opposite.
“Devolve” isn’t a proper use of the word in this context, of course. It means to transfer power to a lower (governmental) level. Perhaps the best word might be “entropy”. One definition of entropy is: A measure of the loss of information in a transmitted message.
As a matter of fact, there is.
The Earth itself provides some evidence.
Given 4.5 billion years in emerging from some unknown but likely catastrophic astronomical event, life is now present on our evolving Earth.
Very good arguments. I think we are tangential, but let me address your points as best as I can:
>>But the answer I was replying to was your statement that vestigial organs are proof of evolution. They are not.<<
I really meant evidence of more than proof.
>>“Evolve” doesn’t mean just to “change” it means “develop gradually, esp. from a simple to a more complex form”. Vestigial organs would be evidence of the opposite.<<
But you apply a very limited view of “to develop.” We no longer have tails, but have vestigial attachments for one. Certainly a tail is more complex than a flat butt, but for us it was no longer needed. At points along the continuum, what was to be Homo Sapiens I am sure it appeared “we” were losing more than gaining. But it is a complex process and it is hard to gauge the evolutionary forces against which we are now pitted.
>>. One definition of entropy is: A measure of the loss of information in a transmitted message.<<
It is one definition, but I don’t think it applies to Homo Sapens nor other evolutionary paths.
>>
never seen a can produce anything other than a cat. never seen a human produce anything buy a human. so when did that stop?<<
You have lived for a billion years? Wow, maybe you have a point if you have.
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i dont get it?
Species change gradually — it takes millions and sometimes billions for someone to “see” a change.
how do you know?
We have billions of fossils and other correlated data from across the spectrum of science, including physical, physics and c chemistry. The OP itself speaks at length of its approach and results.
Sorta beats your “’just because I think so” non-refutation.
But feel free to tell me which of the OP’s approaches is incorrect and how. Or what part of the entire spectrum of natural science is wrong.
Do so and the world is your oyster.
its still all theory not factual proof.
>>its still all theory not factual proof.<<
You need to do some studying — a “theory” is the highest form of scientific analysis.
It is only laypeople who think it is just a guess writ large.
Evolution caught in the act:Hmmm, so was Al's Global Warming.
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