Question

This week we have examined the three modes of Natural Selection: directional selection, stabilizing selection, and disruptive selection. Conduct an internet search for an example of one of these modes of natural selection, describe and share it with the rest of the class. You only have to choose one of the three mechanisms, but you can certainly share more if you would like to.

Examples: The long average length of Giraffe necks represents directional selection. Average birth weight in humans represents stabilizing selection. Disruptive selection was mostly theoretical until recently, see if you can figure out the one example that was found in 2008.

In this assignment, I’m looking to see that you have an understanding of Natural Selection and that you are able to properly cite and reference your discussion board posts.

Answer 1

In directional selection, extreme phenotype is favored over other phenotypes making the allele frequency to shift towards that phenotype in due course of time. Example are: the varying lengths of giraffes' necks in a certain region of Africa in which the selective pressure could be decreased food availability causing the death of shrubs of particular height.

In stabilizing selection, the opposite of disruptive selection takes place which favors the intermediate variants. Example is the average birth size of the baby. If too small, the baby could loose body heat and die and if too big could cause birth complications and die.

In disruptive selection, extreme values for a trait are favored over intermediate values. example is the coluration of peppered moth in England as they can be light coloured or dark coloured with very few in the extremes.