Details of Natural Selection. I Need help.

[Ryan Rudolph]

I generally believe in natural selection as the mechanism driving evolution, but the devil is in the details so to speak.

There has been a nagging question I have had for years, a question I have asked many professors, and even members here, and I have never been quite satisfied with the answer. Perhaps this dissatisfaction is caused by my inability to correctly imagine the answer, or maybe the answer is not the right one, and so this question persists, in my mind, coming to the surface every now and again.

Allow me to explain:

Take the finch experiment of Darwin. He observed several finch species from the Galapagos islands seemed not only related to each other, but also related to the parent species from the mainland. The island birds seemed to have evolve a different size and shaped beaks to allow them to eat the prey that was unique to that island.

Now, my question was how does natural selection work? how does the gene responsible for the trait change over time to match the changing environment?

The most common answer I have gotten is that there are random mutations in the genome for every trait that eventually result in changes to the trait that the environment is putting pressure on, and the most adapted trait survives, while the others disappear.

However, the first question that arose is - isn't it quite rare that a coding random mutation would result in a complete change in a trait in the first place?

And the next question is - how rare is it that this random mutation would also consequentially match the changing environment that the organism moved into that put pressure on that one particular trait?

Moreover, that seems like winning the lottery to me, and if the odds are that low that any of this should happen, it doesn't seem to make sense, considering how a species can face significant changes over a short time. Another problem I have with the 'random mutation theory' is if its true, this means that every trait of a species is constantly being mutated, and tested by the environment, but this would mean that random mutations would result in the finches having a large spectrum of beck size differences, along with differences in every other trait imaginable, but that sort of inefficiency doesn't make sense to me, especially when some of the environmental changes happen over a short period of time, and do not threaten any of the other traits.

And I have had biologists laugh at me when I question this theory of how natural selection works, but in other sciences, such as physics, Einstein made observations such as god does not play dice, or everything happens for a reason, and even though "random mutation of genes' is a reason, it doesn't seem like the right one to me, as some of the best scientific theories are quite simple, elegant and have a certain beauty to them. This theory feels awkward, clumsy, and lacking in refinement.

Any thoughts?

[Robert]

Ryan,

I don't have an answer, but you could try posting your questions in the Evolution & Natural Selection section at RationalSkepticism.org.
http://www.rationalskepticism.org/evolution/

The site/forums has been around since February this year as a result of Richard Dawkins' decision to close the forum on his site, and is populated by a lot of ex members.

[Diebert van Rhijn]

isn't it quite rare that a coding random mutation would result in a complete change in a trait in the first place?

Natural selection just selects by reproductive succes the traits already present. This is not the same as having mutations or with genetic drift, and happens in a whole different timescale (could be fast, during disastrous changes of the environment).

With the finches it was not genetic drift or mutation causing the differences between the populations. It was more a mix between hybridization (there was actually possible contact between distant populations) and selection on existing traits, variation in existing genome, some of which might be recessive or deactivated. Also check out adaptive radiation.

So with evolution you need to make distinction between adaptation, genetic drift [statistical redistribution], gene flow, mutations [errors, viruses etc], natural selection and speciation. One mutation doesn't map to a change in trait, or not a noticeable one at least, or if it does, the chance the organism would survive the change is near to zero. So most mutations, if not repaired right away, will just sit there, inactive, but might arise by recombination once in a while. Also, many traits are caused by a combination ('cooperation') of genes and a mutation could only slightly change a trait, not "completely' modify it.

[Ryan Rudolph]

Diebert,

It has become obvious from your answer that there are quite a few side concepts and processes that directly relate to natural selection that I fully hasn't understood yet. I will take some time to research these, and post some additional questions if they arise. Thanks for the response.

[1456200423]

Now, my question was how does natural selection work? how does the gene responsible for the trait change over time to match the changing environment?

And the next question is - how rare is it that this random mutation would also consequentially match the changing environment that the organism moved into that put pressure on that one particular trait?

Any thoughts?

Organisms adapt by calling up genes that they already possess.

http://www.panspermia.org/oseti.htm

[Ryan Rudolph]

Diebert,

Thanks for your response, as you have proved to be quite knowledgeable on the subject. Some of these biological ideas have always eluded me.

Natural selection just selects by reproductive success the traits already present. This is not the same as having mutations or with genetic drift, and happens in a whole different timescale (could be fast, during disastrous changes of the environment).

Okay I follow you there. Natural selection acts on traits already present in a population.

With the finches it was not genetic drift or mutation causing the differences between the populations. It was more a mix between hybridization (there was actually possible contact between distant populations) and selection on existing traits, variation in existing genome, some of which might be recessive or deactivated. Also check out adaptive radiation.

Okay, so you have a mainland finch that was able to breed with a closely related finch on the island, and the island finch had the beak size trait that was passed on to a certain number of offspring, and those survived better then the ones who didn’t inherit the trait for the correct beak size for the local food.

So there are a few concepts that I need to go into; genetic drift, adaptive radiation, adaptation, gene flow, mutations, natural selection and speciation. I will define each term, and then comment, and if I’m off track, perhaps you could add a comment yourself.

Genetic drift: An overall shift of allele distribution in an isolated population, due to random fluctuations in the frequencies of individual alleles of the genes.

Response: The example I read about is a low frequency trait disappearing because the parents do not reproduce. So can it be a loss or gain of alleles?

Adaptive radiation: the development of many different forms from an originally homogeneous group of organisms as they fill different ecological niches

Response: So the moving of a population into a totally different environment acts on different traits, keeping some and eliminating others? Correct?

Adaptation: Adaptation is the evolutionary process whereby a population becomes better suited to its habitat. This process takes place over many generations, and is one of the basic phenomena of biology.

Response: no questions; seems clear enough.

Gene flow: In population genetics, gene flow (also known as gene migration) is the transfer of alleles of genes from one population to another.

Response: Does this happen because two populations breed, causing new alleles to express in those environments, the example I read about was a population of green beatles allowing a brown one to breed with its population adding that trait to the genepool for that species, correct?

Mutations: Mutations are changes in the DNA sequence of a cell's genome and are caused by radiation, viruses, transposons and mutagenic chemicals, as well as errors that occur during meiosis or DNA replication. They can also be induced by the organism itself, by cellular processes such as hypermutation.

Response: no questions; seems clear enough.

Natural selection: survival: a natural process resulting in the evolution of organisms best adapted to the environment.

Response: no questions; seems clear enough.

Speciation: The formation of two or more genetically distinct groups of organisms after a division within a single group or species. A group of organisms capable of interbreeding is segregated into two or more populations, which gradually develop barriers to reproduction.

Response: no questions; seems clear enough.


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