Currently maintain a significant proportion of the world’s biological diversity seems to be possible only through the maintenance of organisms in their wild state and within its existing range. This is generally preferable to other lines of action because it allows continuous adaptation of populations in response to natural evolutionary processes and, in principle, the continuation of current practices in use (although they often require increased administration).Viable populations of many organisms can be kept for breeding or in captivity. Plants can also be maintained in seed banks and germplasm collections; similar techniques for the preservation of animals are being developed (the storage of embryos, eggs and sperm) but are more problematic.
In any case, preservation outside the place of origin, ex situ obviously only possible for a small part, is extremely expensive and often involves a loss of genetic diversity by the high probability of inbreeding (founder effects; v. gr. a Venezuelan family of Lake Maracaibo, about three thousand people-is descended from a German sailor carrying the gene for chorea (Huntington), the incidence of this disease among existing members is 60%, so this factor effect is called the “founding member”).
Source: http://www.biotech.bioetica.org/clase3-7.htm
