How many pairs of a single species of animal is necessary to preserve a healthy gene pool for that species?

This is not known. Scientists are currently researching this with new tools and can now analyze genetic diversity by studying the DNA directly. There is no set numerical answer in any event.

Such factors as the size of the animal, its reproductive rate, the variation and stability of the environment, competition from other species, geographical range, all are important factors. If a species has a sufficiently safe and hospitable environment it can recover from what is called a small population genetic bottleneck to become diverse again. Remember that mutations occur from time to time.In practice many species many times have colonized new islands or continents with just a few individuals and have developed healthy, diverse populations.

In fact, they may evolve into a variety of species each with its own healthy genetic diversity; that's what the whole story is about the Galapagos! But more individuals means more safety for the species, other things being equal. This is clearly especially true if the species or its preferred environment is under stress, as is the case with all endangered animal and plant species.

With regard to humans, it is believed by many reputable scientists that the population dropped to a few thousand (less than 10,000) at least once during the past million years. This is basic population biology, I just notea few sources but there are countless ones. They tend to be textbooks and journals not internet pages though.

Wikipedia has good summaries of some of the factors.

We are coming from http://www.mahalo.com/answers/shortly-after-take-off-on-a-space-mission-to-mars-planet-earth-gets-hit-by-a-major-meteorite-destroying-all-civilization-what-do-you-do How quaint. ....ok now a more realistic question. :o) Between 50,000 to 500,000 humans would be able to sustain a healthy natural reproductive gene pool.

With cloning that number would shrink dramatically. However no one has investigated weather or not human cloning would break down the human cellular dna sequence over time. ( Think copy of copy of copy ) Mainly because human cloning has been outlawed by the scientific community as "playing god" .

And I don't blame them for their concern. The tree of life happened over the course of hundreds of thousands of years. youtube.com/watch?v=qabl5eIba2g I would say the ideal number of humans would be around 400,000 to preserve the human *genome*.

This is a relative number and what the scientific community is now predicting. Its also the main curriculum in the new england journal of medicine.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.