Is close enough good enough?

[gubba]

G'day Folks,

 

Been musing about mutations a bit lately after brushing up on genetics recently. An oft- stated axiom in evolution is the non- purposiveness ( strewth! is that english?) of natural selection, often followed by wonderful examples of nifty pieces of biological engineering such as binocular vision, flight feathers etc. etc. The descriptions of these adaptations nearly all tend to rave, in deterministic language, about how they were developed to their current level of excellence. Ring bells with anyone?

 

I don't know, but I reckon I wouldn't mind my sight reaching into infra-red, I certainly won't complain if I possessed a better designed spine for our bipedal existence, mind I don't get around so much anymore. My point is that, perhaps, natural selection is not so much about selecting the Fittest as culling the truely Abysmal! If we back off a bit from our species hubris and look across the fossil record, species don't tend to hang around too long no matter how marvellous many of them must have been. And ALL THE TIME THE GENES WILL BE MUTATING. Could mutation, or rates of mutation, be the largest determinant of species' viability? Why is there so much redundancy (no quite what I mean) in our genes? I'm very attracted to the idea that they serve as fall back positions in case of faulty genes etc.

 

Anyway all the above lets me proclaim the laid back musings of evolution, we get along as best as we can 'til the s**t hits the fan and lets hope it ain't in our lifetime. Some of us spread a bit wider, some slow a bit, some even pick up a couple of tricks, but life rolls along much the same just changed a bit, so a couple of us drop off or fall asleep. Still once everyones' got their eyes open you'd be an idiot to close your own tight shut. cheers gub.

[Fishteacher73]

As you speak about mutation rates and viability of species...makes me think about sharks.. Possibly one of the older groups that are still about. It has been said that UV radiation is one of the largest causes of genetic mutations. Water filters out UV quite well at moderate depths...Perhaps this is one reason they are still about...

[gubba]

G'day Fish,

 

Good point! Not only sharks but a few species of fossil fish have been dragged out of the depths in southern waters over the years, still, that does not explain the longevity of crocodiles as a species. Some of the life of our rocky shorelines go back a very long way as well if my memory is not leading me astray, I think even abolone is relatively old? The point here being that species like abolone don't expose themselves to the sun and what's rock like as a UV filter? cheers gub.

[Fishteacher73]

Crocs have very thick skin and boney plates. I would venture to say that these also are good UV filters..Carbonate shells are probably pretty good filters, there is no living tissue, I believe that UV has reasonably close absorbtive properties as visable light, but I could be wrong on that.

 

But speaking of rocky shores...one thing I forgot that toatally blows this idea apart (at least to a degree)..stromalites..not much covering, right at the surface...oh well...

[nkt]

There is no reason why anything shouldn't be free to mutate wildly. Of course, for something to stay the same for a million years, it would suggest that the selection pressure was for the current feature set. Anything a bit better will be selected for, so that will become the dominant form. Once it has reached that plateau, it can stay like that for a million years, as long as nothing else changes and selects against it.

 

Of course, as a friend once said, "Evolution is hard on Aardvarks and the causes of Aardvarks"! Over-specialism is sure to kill you when things change, as you will have far further to adapt than the less successful who have yet to adapt fully to current conditions. If they get there first, they out-breed you, and you wind up having to find another place to evolve to.

[Fishteacher73]

The genetic replication mechanism are pretty effecient. Even if there are transcription errors they are often repaired. The main driving force seems to be not particularly mutation, but selective breeding of succesful individuals within the phenotypic spectrum. For example, if a population of animals finds that a larger trait A (arm length, lung capacity, whatever) is advantageous, those in the normal population with the larger trait will be more successful and produce more offspring. The median measure for trait A will then over a few generations be larger than it started. His is notr from mutaion but natural selection pressure opting for a better fit individual withing the normal phenotype. You will have shift but not mutation. This is how much adaptation occurs.

This is not to say that mutation is not a vital role in species evolution, but genetic drift is a more common one.

[gubba]

G'day Fish,

 

Any idea on how much variability is feasible in your "normal phenotype", there's commonly a circuliarality to the arguments around mutation and drift etc. that strike me as the best signposts for more research that my foggy old brains can recognise. cheers gub.

[Fishteacher73]

That variation is debateble. It has to do with definition of species. There are corals that look very much alike, but are distinct species, while there are species that have vastly different morphological forms.