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Theory of Evolution, Natural Selection

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According to the Theory of Evolution, Natural Selection is the mechanism by which evolution occurs. Remember: evolution occurs at the level of the population. Individuals do not evolve, populations evolve.

The process of Natural selection is based on the following four postulates [listed in your textbook (Audersirk, 2008) on page 288]:

Postulate 1 - Individual members of a population differ from one another in many respects.

Postulate 2 - At least some of the differences among members of a population are due to characteristics that may be passed from parent to offspring. That is, they are heritable or genetic.

Postulate 3 - In each generation, some individuals in a population survive and reproduce successfully but others do not.

Postulate 4 - The fate of individuals is not determined by luck. Instead, an individual's likelihood of survival and reproduction depends on its characteristics. Individuals with advantageous traits survive longest and leave the most offspring, a process known as Natural Selection.


Choose ONE animal species. Your goal is to describe the way in which an evolutionary change might occur for a particular characteristic (trait) of a population of that species as a result of natural selection.

The characteristic (trait) could be something like coloration pattern, length of the limbs, size of the teeth or beak, or any measurable trait that is inherited.

The organism you choose should be a real one but the evolutionary change in a trait that you describe can be real or fiction.

In your own words,

Explain how the change in this trait occurs. You will describe the trait in the population at the starting point and then what the trait will look like at a later time, as a result of natural selection.
Make sure to explain the process by which the changes occurred. What is the selective pressure? Explain why the change might confer more fitness to a particular environment?
Tips: Make sure to include the following in your answers to a and b above:

Clearly state the name of the SPECIES you are going to be talking about for this assignment. (Make sure you know what is meant by a species.)

Also, clearly state what population of the species you are going to talk about by specifying its geographic location. (Make sure you understand what a "population" is.)

Clearly state the characteristic (trait) of the population that you are going to be talking about and explain how this trait varies among individuals.

Explain what change occurs in the environment that causes a change in the above characteristic (trait)?

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Solution Preview

To the postulates above, all coming from Darwin, (who did not know much about genetics - except some practical agricultural & husbandry breeding, he lived in the countryside and owned an estate there after all as well as being a biologist) we have to add that random chance guided genetic mutations happen all the time. If they are beneficial in the environment at hand they will help the offspring according to postulates 2 to 4.
The animal species I have chosen is the modern human species homo sapiens. The population I have chosen is modern European Caucasians. The example I use is my own family on my father's side going back father to father as far as it is possible to come. The trait of study is skin color and why that has changed. I live in Sweden and am a rather typical European male (northern west European). Historically I know that my family came to modern Sweden from eastern Finland (Karelia) - but at that time Sweden and Finland were one single country which ...

Solution Summary

According to the Theory of Evolution, Natural Selection is the focal topic.