Strength in Numbers
08/08/12 12:57 Filed in: GenomeWeb Daily Scan
Submitted by S. Pelech - Kinexus on Wed, 08/08/2012 - 14:30
Preservation of habitat that is rich in biological diversity seems to be the best solution to ensure survival of most species facing extinction. Some 40% of all animal species today appear to be under threat of extinction, but more than 99% of all of the animal species that have ever swam, walked or flew on this planet are forever gone. It seems that new species emerge when the numbers of the predecessors of these species actually dwindle or become geographically isolated. Apparently, the rate of evolution of new species is accelerated after mass extinctions, such as occurred about 65 million years ago with the demise of the dinosaurs. Genetic evidence points to the near extinction of our own direct ancestors about 200,000 years ago. More recently, whales have made a bit of a come back in the last few decades after their populations were decimated more than 95% by a few hundred years of whaling practices. In these examples, genetic diversity was not really the critical factor for the survival of these species.
It is intuitive that sheer numbers of individuals within a species would be a critical factor for a species' survival. With a larger population, it might seems that there would be greater genetic diversity as well, since there would be a more chances for accumulation of natural genetic mutations within the population. However, this is not necessarily true. For example, there is greater genetic diversity amongst individual members of the other primate species than there is in humans. When one looks closely at the various genes encoded in diverse animal species, the number of genes and their nucleotide sequences are remarkably similar. It seems that phenotypic differences arise primarily from where and when the proteins encoded from these genes are produced.
The most critical factor for the emergence of new species is likely to be the genetic variation related to the specific locations of genes on individual chromosomes. The vast majority of mutations within the coding sequences are inconsequential for the survival of a species or the emergence of a new one. But chromosomal rearrangements can result in non-viable embryos following fertilization. With dwindling populations and a higher probability of in-breeding, there is improved chances that the similarly rearranged chromosomes from an egg and a sperm can properly align following cell fusion and later reductive cell divisions so that each daughter cell will have two copies of each gene. This becomes most critical for the production of gametes later on, which in their haploid state must have a copy of each gene for the next generation. These considerations are likely to apply equally to both animals and plants that reproduce sexually.
Link to the original blog post
Preservation of habitat that is rich in biological diversity seems to be the best solution to ensure survival of most species facing extinction. Some 40% of all animal species today appear to be under threat of extinction, but more than 99% of all of the animal species that have ever swam, walked or flew on this planet are forever gone. It seems that new species emerge when the numbers of the predecessors of these species actually dwindle or become geographically isolated. Apparently, the rate of evolution of new species is accelerated after mass extinctions, such as occurred about 65 million years ago with the demise of the dinosaurs. Genetic evidence points to the near extinction of our own direct ancestors about 200,000 years ago. More recently, whales have made a bit of a come back in the last few decades after their populations were decimated more than 95% by a few hundred years of whaling practices. In these examples, genetic diversity was not really the critical factor for the survival of these species.
It is intuitive that sheer numbers of individuals within a species would be a critical factor for a species' survival. With a larger population, it might seems that there would be greater genetic diversity as well, since there would be a more chances for accumulation of natural genetic mutations within the population. However, this is not necessarily true. For example, there is greater genetic diversity amongst individual members of the other primate species than there is in humans. When one looks closely at the various genes encoded in diverse animal species, the number of genes and their nucleotide sequences are remarkably similar. It seems that phenotypic differences arise primarily from where and when the proteins encoded from these genes are produced.
The most critical factor for the emergence of new species is likely to be the genetic variation related to the specific locations of genes on individual chromosomes. The vast majority of mutations within the coding sequences are inconsequential for the survival of a species or the emergence of a new one. But chromosomal rearrangements can result in non-viable embryos following fertilization. With dwindling populations and a higher probability of in-breeding, there is improved chances that the similarly rearranged chromosomes from an egg and a sperm can properly align following cell fusion and later reductive cell divisions so that each daughter cell will have two copies of each gene. This becomes most critical for the production of gametes later on, which in their haploid state must have a copy of each gene for the next generation. These considerations are likely to apply equally to both animals and plants that reproduce sexually.
Link to the original blog post