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?
Alleles are matching genes; one from our biological mother, one from our biological father. We have two copies of every gene (strings of code that drive some biological function on our chromosomes)
In biology, evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection. The forces that cause these characteristic changes are mutation, gene flow and genetic drift.
Jean Baptiste Lamarck put forth the theory of inheritance of acquired characters, which is also known as Lamarckism. It was published in ‘Philosophie Belgique’ in the year 1809.