Freethought & Rationalism Archive

Third_Choice · 04-03-2007, 01:52 PM

Quote:

Originally Posted by Non-praying Mantis

Because when one female breeds parthenogenetically, she produces an exact (except for mutations) copy of herself. This avoids the problems of sexual reproduction with low population levels, namely inbreeding, which can lead to large percentages of lethal mutations.

does sexual reproduction cause a higher rate of mutation? or are the rates the same for mitosis and meiosis?

further, two cockroaches would be enough to start a viable population. i know thats not the same as two people, but for many species, probably most, thats all it would take.

Third_Choice · 04-03-2007, 02:03 PM

Quote:

Originally Posted by RAFH

Reproduction isn't the issue. Its the viability of the resulting population. A single individual could clone but the offspring would be very similar to the parent. If that continues for very long, the resulting population would be very, very similar and highly susceptible to predators or diseases that evolved quicker or the occasional natural event. In other words, what kills one, if they are all similar, will likely kill them all.

and yet there are plenty of species that reproduce with only females. plus, if you were to look at any of these species over their ranges, im sure you would find plenty of variation, especially as you go from one extreme of their range to another (heat, elevation, etc).

Quote:

That's why evolution isn't just a handy modifier of life, its essential for life to persist. If you had a single species with clone like similarity, what happens if the climate suddenly changes?

they continue to survive and populate the entire earth with their descendents leading to the variety of life we have today?

further, sex is not required for evolution. somehow all your models assume that the first organism existed in a large population of sexually reproducing highly varient individuals.

Quote:

Whoops, the slight variability allowed by simple mutation most likely will not be sufficient to allow that single species to survive as a population. What if their food source fails? There are many possible sources of extinction for a highly homogenous, unchanging species, much more than for a highly addaptive, quickly changing species.

again to use the cockroach example. 2 cockroaches will eat just about anything and survive in a wide variety of conditions. given a couple generations, the population will number in the thousands. many species on the planet are like this.

once the population covers a large enough range to have environmental variablitity, selective presure will ensure that the populations begin to diverge and you will end up with a large genetically variable population.

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