Monday, August 14, 2006

Some thoughts on Evolution

Most evolutionary scientists accept Evolution as fact. Problems only arise when deciding how it occurs. There are several theories, and perhaps all may play a part,
though surely Darwin's natural selection acts in combination with the other theories, and is the architect.

When Mendel found the mechanism for variation, it solved Darwin's dilemma of not knowing what enabled the variations. Later neo-Darwinism was born with the uniting of Mendelism and Darwinism, which accounted for the gradual evolutionary change. Yet as Darwin knew with the breeding of dogs and pigeons that there is a great amount of variation stored in each species which enabled breeders to change their shape and size,.Plants and animals can adapt to the environment by making use of the great variation stored in the genes, but this is is not in itself evolution. If the environment changed back to its original status so would the species change back too.Over many many generations this adaptation may bring about a new species if separation prevented any gene mixing. I feel that its not just the appearance of the species that will make for a new species but a fundamental change in its physiology which will prevent it breeding with the species from which it was separated. That is why pigeons breeds have never become separate species.There would have to be a change in their physiology.

Punctuated equilibrium is another theory, advocated by Stephen J.Gould. This means that after a great extinction there where many niches open to the surviving species.They were able to explode into the vacant ground and evolution and speciation was rapid eventually ending in a period of stasis. This may well be correct with natural selection playing its part. During this so called stasis period slow evolution continued to fine tune with natural selection still the architect. Invasive plants do the same, moving out of their natural environment with all the constraints of co evolved partners, parasites and competition holding them in place,they are freed to adapt or even evolve to spread unhindered into their new environment.

Lynn Margulis makes a great deal of sense with her symbiogenesis whereby plants join together for their mutual benefit as in the Azolla fern in my pond.
Genetic variation is proposed to mainly occur as a result of transfer of nuclear information between bacterial cells or viruses and eukaryotic cells.
see also
Then there is the hybridisation of two species which produce more competitive individuals, which will eventually cause the extinction of the parent species and they themselves will become a species in their own right. Up to now it sees the only examples I have,have been brought about by man.
see article on wild radish

Killer bees were the product of the African bee and the European. Neither of these species were overly aggressive. I have had experience with both of them.The hybrid now seems to have adapted pretty well and has invaded much of the territory to the north from where it escaped.
see article on fire ants
read about how hybridisation improves adaptation
So these are cases where the evolutionary branches have actually joined together again. I'm sure this is a natural process occurring all the time but we can never find it in the


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