Viviana Herrera Assignment 2 Evolution is a process that take place after a great number of generations This process includes certain forces that do present visible changes through generations These forces are natural selection mutation genetic drift genetic flown population mating and mating preference The chapter five of the book The beak of the Finch we can observe that the author illustrate how natural 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 males and females due to environmental change and food scarcity now there were more males than females This means that not all males were going to mate As a result females could pick their mates according to their mating preference The observations of the team showed that females choose the larger of the largest males as mates This preference affected to the next generation of 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 fittest characteristic forever In chapter seven the team experienced a change in the environment This change was produced by the presence of El Ni o which is a meteorological phenomenon This phenomena increased the percentage of rain As we all know with an increase in rain plats develop faster and the availability of seeds increase This increase on the land fertility produced a curious change on the sexual behavior of finches As it was mention in chapter 5 the gene flow was limited because there were a small population of female finches Nevertheless due to the increase 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 now there are more finches than the previous generation Viviana Herrera This environmental change not only produced a change on the number of finches but also on their survival rate Chapter seven shows a loss of the directional selection now the finches that were surviving were not the big ones but the small ones The natural selection that was originally favoring the big finches now was killing them As we can observe natural selection is subjected to the environment and it can change at any time that is why according to Darwin it is only one aspect of evolution For evolution to happen it is needed the union of all evolutionary forces Mutation as an evolutionary forces is mentioned in chapter 15 According to the researchers the stress that a rapid environmental cause on an individual can produce mutations For mutations to spread it is needed an interaction among different populations In that way the genetic flow varies However as the population of finches are geographically isolated the possibilities of stead mutations is lower This situation lad us to chapter 16 which talks about the introduction of new species in a different environment This will bring a chance for mutation to spread because eat will increase the flow of genetic material However this can alter the ecosystem and pressure on the existing species