Viviana Herrera Assignment 2Evolution is a process that take place after a great number of generations. This process includescertain forces that do present visible changes through generations. These forces are: naturalselection, mutation, genetic drift, genetic flown population mating and mating preference. Thechapter five of the book” The beak of the Finch” we can observe that the author illustrate hownatural selection and mating preference can produce a notable difference between generations.The Grant team found that even thought at the beginning there were an equal number of malesand females, due to environmental change and food scarcity, now there were more males thanfemales. This means that not all males were going to mate. As a result, females could pick theirmates according to their mating preference. The observations of the team showed that femaleschoose” the larger of the largest males” as mates. This preference affected to the next generationof finches which had a “4 or 5 percent deeper beaks than their ancestors” (Chapter 5, pg. 81). However, it does not mean that being big and having a deep beak is going to be the fittestcharacteristic forever. In chapter seven the team experienced a change in the environment. Thischange was produced by the presence of El Niño which is a meteorological phenomenon. Thisphenomena increased the percentage of rain. As we all know with an increase in rain platsdevelop faster and the availability of seeds increase. This increase on the land fertility produced acurious change on the sexual behavior of finches. As it was mention in chapter 5, the gene flowwas limited because there were a small population of female finches. Nevertheless, due to theincrease of the food availability the next generation started reproducing earlier than they should.This increase on the reproduction rate caused a genetic drift on the population. It means that nowthere are more finches than the previous generation.Viviana Herrera This environmental change not only produced a change on the number of finches but also ontheir survival rate. Chapter seven shows a loss of the directional selection, now the finches thatwere surviving were not the big ones but the small ones. The natural selection that wasoriginally favoring the big finches now was killing them. As we can observe, natural selection issubjected to the environment and it can change at any time that is why according to Darwin it isonly one aspect of evolution. For evolution to happen it is needed the union of all evolutionaryforces. Mutation as an evolutionary forces is mentioned in chapter 15.According to the researchers, thestress that a rapid environmental cause on an individual, can produce mutations. For mutations tospread, it is needed an interaction among different populations. In that way the genetic flowvaries. However, as the population of finches are geographically isolated the possibilities ofstead mutations is lower. This situation lad us to chapter 16, which talks about the introduction ofnew species in a different environment. This will bring a chance for mutation to spread becauseeat will increase the flow of genetic material. However this can alter the ecosystem and pressureon the existing