Реферат: Evolution Essay Research Paper 1 Describe modern

Evolution Essay, Research Paper

1. Describe modern theory of evolution. Evolution simply describes the changes over time that occurs in organisms. Evolution as a whole can be more clearly describes by subdividing it into two separate categories macroevolution and microevolution. Macroevolution is evolutionary change on a grand scale that occurs over long period of time. It is essentially the formation and extinction of species. Microevolution, however, is evolution within existing species. In a larger sense, macroevolution occurs when a lot of microevolutionary changes occur. The foundation of how both these types of evolution occurs is in natural selection. Natural selection is the passing from generation to generation characteristics that have allowed parent generations to survive. On the other hand, characteristics that are weak or not fit for the environment and survival are not passed down due to the fact that most individuals carrying the trait will not live long enough to have offspring. Therefore, it is evident that natural selection is a product of changing to adapt more effectively to the environment itself. This process as a whole is know as the modern theory of evolution. 2. Factors or processes that influence and change gene pools. What is the relation to natural selection? Four basic factors influence and change gene pools: mutation, migration, genetic drift, and non-random mating. While mutations cause changes within species, the rate at which they occurs is generally so low that it will generally not effect the Hardy-Weinberg equilibrium. However, it still provides for genetic variation and thus evolution. Migration is simply the movement of individual from one population of species to another. It is overtly related to natural selection because if a population migrates and it is more suited to the new environment then it can survive and mate there successfully. Genetic drift can be more clearly observed in small populations where some alleles can be lost and allele frequencies can randomly change. This is related to natural selection because some individuals with certain allele combinations may be more fit for an environment and will proliferate successfully in that habitat. Non-random mating hinders natural selection because it does not allow populations to mate randomly and therefore natural selection cannot occur. Basically, non-random mating produces a higher rate of recessive alleles with may be harmful to the individual. Also, since the gene pool is narrowed, the fittest organisms may not be produced. 3. Describe process of speciation.Speciation is the formation of new species. There are two types of speciation: allopatric and sympatric. Allopatric speciation occurs when there is a geographic barrier that separates a population. The two populations are then forced to adapt to separate environments. On the other hand, sympatric speciation is the formation of different species within a common area. This change may be due to increased competition for necessary resources, an organism filing a niche. Basically, both types of speciation rely on adaptation and natural selection. Allele frequencies that produce more successful traits are passed on and over time new species are made.

4. Describe what happens in directional selection, stabilizing selection, and disruptive selection. In directional selection the genes that control one extreme of a specific trait are eliminated. Thus, only the moderate characteristic and the other extreme remain. Stabilizing selection is similar to directional selection except that both extremes of a trait are phased out. Therefore only the moderate characteristic remain in this case. Lastly, Disruptive selection favors the extremes rather than the intermediate traits. Only the extreme characteristics are shown. 5. Discuss gradualism versus punctuated equilibrium as mechanisms for evolution. Early scientists, such as Darwin, believed that evolution was a slow and gradual process. They contend that change takes place continuously and along a straight progressive curve. Eldredge and Gould formed the theory of punctuated equilibrium after examining fossils. Their theory states that evolution took place in rapid spurts with long periods of little change. Both are feasible theories and are equally as likely to have occurred. 6. Define words. (See packet) 7. How adaptation is the end result of evolution. Adaptation is the end result of evolution because organisms that adapt best to an environment produce more offspring with advantageous characteristics while organisms that do not adapt are weeded out. Over generation and generations, more advantageous characteristic are predominately shown and the species as a whole has evolved. This group has adapted and is therefore more fit to live in the environment. In our world today, it is evident that our environment has increasingly been subject to changes by humans and industrialization. Industrial melanism shows how species have evolved to adapt to pollution. In this process darker species are better able to survive due to a darkening environment. Darker moths can hide more easily from predators and therefore this type of moth in cities has evolved in color to better fit its environment. Another example is a type of grass that can tolerate higher amounts of lead. Around mining areas, grasses that were more tolerant survived while other grasses died off. Therefore a new breed of lead-tolerant grass slowly came into being. Furthermore, as shown in the video, sickle cell anemia is very high among African and low among African-Americans. As we know, the anemia gene is also responsible for resistance to malaria. In Africa, people with one allele of the sickle cell gene are more adapted to the environment which carries malaria. However, in America, where malaria is virtually non-existent, the rate of sickle cell anemia is really low. Therefore, sickle cell anemia shows the how the African race has evolved to have more of the sickle cell gene due to adaptation to the environment.

еще рефераты
Еще работы по на английском языке