Ashley's Evolution Blog

I think that one major reason genetic variation is still present is because oftentimes the strength of selection is not strong enough to completely eliminate a certain trait. While some are more advantageous to have, other traits are still able to survive and reproduce enough to maintain that trait being present in the population. There are different levels of selection, and depending on how strong it is will determine how much variation there is in a population for that trait. Mutations will also always arise in populations and there is often a new advantageous trait to have. Generally if these mutations are advantageous, they may be able to fixate in the population. If traits are constantly changing, then there will always be variation in a population. It would be very difficult for all members of a species to obtain a trait if the alleles for this trait change often. As seen in some R exercises, phenotypes that are not advantageous may still be difficult to eliminate from a populati...

  The theory of neutral evolution refers to random molecular level evolutionary changes that are caused by mutations of nucleotides. On the other hand, evolution by natural selection implies that individuals with the most advantageous phenotypes, who are better adapted to their environment, will pass their genes on to their offspring. One main difference is that neutral evolution focuses on a genetic level, the nucleotides of the genome, while the phenotype is what impacts natural selection. These driving forces of natural selection are based on fitness, and the phenotypes that are selected for will be more likely to pass on their genotype. The opposite is true for deleterious genotypes, as their phenotype is not selected for it will removed from the population. The neutral theory does not take into focus the effects of natural selection, just genetic drift. Alleles have the ability to become fixed if they are neutral or advantageous, which is not as prevalent in the theory of evol...

     I used to only think about inbreeding when it applied to humans, and how this often lead to genetic diseases, but never thought about why this is so or the other affects it had. I now know that inbreeding affects the HWE, but not evolution. This is because inbreeding causes an excess of homozygotes and does not allow for the prediction of genotype frequencies from the allele frequencies. In humans, inbreeding causes genetic disorders that are often homozygous recessive diseases. Additionally, inbreeding may occur in species of animals that are endangered or are kept very close together. Plants self-fertilizing is very common as well, but this is not often seen as a negative thing.     Some possible benefits of assortative mating may be the fixation of beneficial alleles in a population. In some cases, it may be more beneficial to be homozygous and inbreeding would avoid having an unsuccessful, heterozygous offspring.     In each situation, it high...

Each island seems to have a different phenotype that is advantageous depending on the island. A,B, and C are mostly selected for on islands, as their reduced and lack of stripes are adapted to their environments. However, the mainland dominates with snakes which have phenotype D, as their stripes would be most beneficial to have in their leafy forest environment. Any snake that migrates from the mainland would stick out to predators since they do not have the camouflage that the other snakes have: reduced or lack of stripes. Similarly, snakes that migrate from the islands to the mainland would not have the stripes to camouflage them in the leafy environment. This has the consequence of making migration from island to mainland (and vice versa) very difficult. However, the graphs show that phenotype D, the striped snakes, were able to survive on the islands. They are present in a much smaller number than the other phenotypes, but they still have the ability to survive there. In the Ontar...