@@MRSA has evolved, along with other stuff
Martin Yirrell posted Thursday 2nd October 2008 17:43 GMT, in response to Peter Mellor:
>I haven't the faintest idea what you mean by "loss of information",<
Genetic material is effectively information on the variable features of the form of life encoded in a highly efficient manner. Mutation is the result of damage to the material and is the loss of genetic information.
The genetic code represented in DNA defines the form of life (phenotype), including its "variable features". If the genome changes, then the expressed phenotypes changes also (generally speaking). The encoding is NOT done in a "highly efficient" manner, as several commentators have remarked. You have to define "efficient". (Human-designed codes require "redundant" bits of information in order to detect or correct errors. Does the inclusion of "redundant" bits render these codes "inefficient"?) There is now good evidence (see earlier postings) that the genomes of most species are inefficient, and include large quantities of "junk" which no longer have any discernible effect upon the phenotype.
Mutation can be due to damage (e.g., by radiation), or to imperfect copying of DNA during cell division (since no copying process can be guaranteed to be totally error-free).
Over millions of years, the DNA molecules in the cells of living organisms have accumulated information, rather than lost it, overall. They may have lost some information, but this has been replaced by a greater amount of different information.
Although many mutations are fatal for the organism (the resulting phenotype), a few are either neutral or beneficial (i.e., they do not impair, or improve, the probability that the organism will survive long enough to transmit its genes to the next generation).
>Note: "It has EVOLVED ..."<
No, actually it hasn't evolved, it is "a resistant variation of the common bacterium Staphylococcus aureus".
Just as people vary, so bacterium vary. Some people have genetic illnesses, some people have red hair, it is not evolution it is variation.
The existence of a "resistant variation" is the basis for the evolution of a resistant strain compared to the original non-resistant strain. This is the definition of "evolution". Variation between individual bacteria (in this case, being more resistant to, or less resistant to, being killed by methicillin) is acted upon by natural selection so as to favour the survival and reproduction of the more resistant individuals. In the presence of methicillin, the more resistant strain will more probably survive and produce offspring.
The *population* evolves (not the individual bacteria), as its gene pool is shifted by natural selection to include more copies of a "successful" gene and fewer copies of the related "unsuccessful" gene.
[BTW: The plural of "bacterium" is "bacteria". The plural may be used to denote many individuals of a single species or several different species.]
>MRSA is a classic example of evolution happening right under our noses. Antibiotics became widely used from the 1940s on. MRSA evolved its resistance in the 1990s (and is not the first species of bacterium to have evolved resistance to at least some antibiotics).<
Now I'm not sure about MRSA but I do know that bacteria resistant to modern antibiotics were found in the frozen corpses of members of an ill fated polar exploration. Selection occurs without Evolution occurring.
I would like to see the reference for the polar explorers.
Your statement "Selection occurs without Evolution occurring." is the totally wrong conclusion to draw here. What has most likely occurred, is *mutation* without *selection*, and hence without *evolution*. Natural selection drives the direction of evolution, acting upon existing genetic variation within the evolving populations.
The fact that bacteria mutated to be resistant to certain antibiotics before these were widely used as medicines, is not surprising.
Consider that bacteria and fungi have evolved together for millennia competing for the same food sources. One trick evolved by certain strains of fungi was to excrete substances (eventually named "antibiotics") which were toxic to bacteria. In response, certain strains of bacteria evolved a resistance to these toxins. This is almost identical to the familiar evolutionary "arms race" between predators and prey.
Long before Alexander Fleming noticed the blank patches in his culture dishes, and we began to splash antibiotics all over the environment, strains of bacteria that were resistant to any given fungal secretions must have arisen naturally.
It is the ubiquitous presence of certain antibiotics in the environment (or at least, some environments) that drives the evolution of resistant strains: whole populations of individual bacteria, each one of which carries the genes to enable it to survive the toxins. This ubiquitous presence has only come about with mankind's intervention. We had a magic bullet and we shot ourselves in the foot with it!
>Speciation arises from evolution<
No, speciation is quite different from Evolution and occurs when variation arises from the selection of information already existing in the genome. It is noteworthy that domestic dogs are considered one species despite a range of variation that, had it occurred naturally, would have resulted in a number of 'species'. Evolution, on the other hand requires the generation of new genetic features that did not previously exist - limbs for example from a form without limbs. Evolution has never been observed.
To deal with your last point first: evolution has been observed wherever living species have been observed. It occurs everywhere and at all times. The fact that it is (usually) a slow process may conceal its occurrence from us, unless we know what to look for. In some cases, we can only infer what has occurred in the past from indirect evidence (e.g., the fossil record) after the changes have occurred. The evidence is still real, however.
I have read "young Earth" creationists trying to argue that we cannot use radiometric dating based on long-lived isotopes, since we have not had time to measure their half-lives! These people cannot get their brains around the method by which a half-life of many thousands of years can be estimated by accurately measuring the decay of a sample over a few months.
The fact that evolution occurs (usually) slowly, by imperceptible increments, poses a similar problem. In particular, the emergence of separate species takes a long time, as does the "generation of new genetic features that did not previously exist". Limbs, eyes, and brains have arisen that did not previously exist, but natural selection takes millennia to do it, acting upon tiny variations between individuals, that are the expression of minor differences between their genomes, resulting in turn from random mutations. (See "Your Inner Fish" by Neil Shubin, to see how the anatomy of the human limb can be traced back to that of our watery ancestors.)
Speciation is the name given to a wide divergence between genetically separated populations. When the difference between them is such that they can't easily interbreed, we say that we have two different species, but the label is a man-made designation. There are countless cases that fall into a grey area, where there is an argument over whether two sub-species are variants of a single species, or separate species?
Appearances can be deceptive. Two species may look similar, but be unrelated. Sharks and dolphins have striking similarities of body shape, but one is a fish, the other a mammal. This can result from "convergent evolution". Conversely, some animals may appear totally different, but be close cousins. The hyrax (http://en.wikipedia.org/wiki/Hyrax) is an animal the size of a large rabbit, but is thought to be fairly closely related to the elephant.
The classification system used by Linnaeus was based upon observable features. It is now being substantially revised in the light of modern genetics. (This knowledge was not available to Linnaeus or Darwin, but it is now totally accepted by scientists that genetic relatedness is the only sure basis of classification of species.)
Domestic dogs are not *regarded* as the same species; by the criterion of genetic relatedness they ARE the same species. The differences in appearance show how rapidly artificial (as opposed to natural) selection can produce changes, but all breeds are descended from the grey wolf (or a common ancestor with the wolf that was around when mankind began to domesticate them). A Yorkshire terrier can interbreed with a great dane: the problem lies in the logistics, not in the genetics! This is one example of appearances being deceptive.
Your statement that: "... speciation is quite different from Evolution and occurs when variation arises from the selection of information already existing in the genome." is completely false. You seem to be implying that different species have the same genome, which is nonsense. We know that different species have different genomes, and the greater the differences between the phenotypes, the more differences there are between the genomes.