Population bottlenecks occur when a population’s size is reduced for at least one generation. Because genetic drift acts more quickly to reduce genetic variation in small populations, undergoing a bottleneck can reduce a population’s genetic variation by a lot, even if the bottleneck doesn’t last for very many generations.
Both natural selection and genetic drift lead to evolution process by varying the gene frequency of a population over time. Both these processes are involved in evolution and are not mutually exclusive. However, natural selection is the only process, which selects the best adaptive organism to the environment, and genetic drift reduces the genetic variation.
In population genetics, evolution is defined as a change in the frequency of alleles (versions of a gene) in a population over time. So, evolution is any shift in allele frequencies in a population over generations – whether that shift is due to natural selection or some other evolutionary mechanism, and whether that shift makes the population better-suited for its environment or not.
HIV virus is one of the most pressing health concerns facing the modern world. Since the first reported case of HIV/AIDS in 1981, over 25 million people have died. Out of the millions of people infected each year with the HIV virus, a few have shown HIV/AIDS resistance. A genetic mutation found mostly in people of European descent delays the progression of AIDS and in some cases even brings about immunity.
They appeared in an evolutionary blink and changed the rules of life for ever. Before eyes, life was gentler and tamer, dominated by sluggish soft-bodied creatures lolling around in the sea. The invention of the eye ushered in a more brutal and competitive world. Vision made it possible for animals to become active hunters, and sparked an evolutionary arms race that transformed the planet.
For much of nature, natural selection and ‘survival of the fittest’ still play a dominant role; only the strongest can survive in the wild. As little as a few hundred years ago, the same was true for humans, but what about now?
Natural selection (aka survival of the fittest) is a mechanism of evolution. Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time.
The whole human family is one species with the same genes. Mutation creates slightly different versions of the same genes, called alleles. These small differences in DNA sequence make every individual unique. They account for the variation we see in human hair color, skin color, height, shape, behavior, and susceptibility to disease. Individuals in other species vary too, in both physical appearance and behavior.
Under occupation, Danish farmers were banned from raising their home country?s flag. In protest against the flag ban, farmers came up with an ingenious idea. The farmers would raise a new pig breed in protest.