Natural Selection Essay

988 WordsApr 30, 20124 Pages
Natural Selection Name Period Date [pic][pic][pic][pic] Recall that there are four parts of natural selection to take place. A) Below is a series of pictures representing changes in a population of cacti. Pictures 1 and 2 show what happened when a deer came to eat, picture 3 shows the cacti a few weeks later (notice the flowers on the right-hand cactus), and picture 4 shows the situation a few months later. 1) What is overproduction? 2) Genetic Variation within the population: In picture 1, what is the main difference between the cactus on the left and the cactus on the right? 3) Struggle to survive: Why would a deer be more likely to eat the cactus on the left than the cactus on the right in picture 1? 4) Differential Successful Reproduction (fitness): What effect does the deer's behavior have on the survival and reproduction of these two types of cactus? 5) Do you think that evolution by natural selection is occurring in this cactus population? (Assume there is actually a large population of cacti, some look like each type of cacti shown above)Explain why or why not. B) Peppered Moth Background: Natural selection is the reproductive success of organisms that are best suited for an environment. It is the driving force of evolution. Natural selection occurs within populations, which are interbreeding groups of individuals of the same species. Genetic variation is one factor that influences natural selection. Genetic variation occurs when a population has multiple versions of a trait. For example, some organisms in a population of moths are dark colored, while some are light colored. Natural selection over time results in adaptations, where certain traits are favored due to their influence on survival. Adaptations over many generations can lead to evolution. Peppered

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