In class on Monday we talked about Speciation, or the creation of new species. What helps drive the process of speciation is natural selection. We learned 4 different aspects of natural selection:

Genetic Variation (mutation)Over Production of OffspringStruggle for Existence (food limitation)Differential Survival & Reproduction (heredity)

A source of genetic variation is mutation, which is considered “the fuel” for evolution. Remember… populations evolve, not individuals. As species reproduce each generation of offspring is different because the parents’ genes mix and the result can be a variety of things. Mutation is random, the behavior, shape or appearance that an organism inherits will not necessarily always be beneficial, although natural selection favors organisms that possess features that give them an advantage in survival. Thus organisms possessing unfavorable traits will die off and their trait will die with them (decreasing their presence within a population).

The 3 types of Natural Selection we learned about are:

Stabilizing: when the “average” individuals in the population are favored of the extremes of a traitDisruptive: when individuals at both of the extremes of a trait are favored over the average individualsDirectional: when individuals possessing an extreme trait at one end of the curve are favored

*Disruptive Selection plays an important role in speciation because as variance within the population increases, dividing the population into 2 distinct groups, speciation becomes possible.

Lastly, we covered 2 types of Speciation:

Allopatric: speciation by geographic isolation. This type of speciation is much like a cheesy movie where the main character goes off having adventures that changes him so drastically that when he returns nobody in his hometown recognizes him. Organisms that were once part of the same population (same specie) and were separated geographical underwent mutation creating new traits only shared in that isolated population, eventually resulting in a new specie. Sympatric: speciation in which new species evolve from a single ancestral species while inhibiting the SAME GEOGRAPHICAL REGION. For example, there is small volcanic crater lake in Nicaragua that is completely isolated, so there is no physical way it could be connected to any other body of water. A study was done on the lake and this is what was concluded, “We find, first, that crater Lake Apoyo was seeded only once by the ancestral high-bodied benthic species Amphilophus citrinellus, the most common cichlid species in the area; second, that a new elongated limnetic species (Amphilophus zaliosus) evolved in Lake Apoyo from the ancestral species (A. citrinellus) within less than ~10,000 yr; third, that the two species in Lake Apoyo are reproductively isolated; and fourth, that the two species are eco-morphologically distinct.” (http://www. nature. com/nature/journal/v439/n7077/full/nature04325.html)

*From Mr. W, the brief video example of allopatric speciation shown in class:

Via:pdsblogs. org

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