Prep 19 Essay Example | Topics and Well Written Essays - 500 words

Prep 19 - Essay Example Speciation is the splitting of a lineage to produce two or more separate species. For this to happen, two or more of the members or species are selectively isolated and allowed to interbreed. When a species population extends over a wide geographical area and mating is selective rather than random, the gene pool is said to be sealed. This reduced gene flow causes the development of new species due to interbreeding. The importance of this is the generation of a pure species that repeatedly improve both genetically and phenotypically. Speciation involves the separation of an original species and the development of two or more pure species usually by a barrier. Allopatric speciation specifically involves the development of a physical barrier between separated members of the species to prevent crossbreeding. This results in geographical separation and hence interbreeding within the new geographical area. This is the dominant mode of speciation and once two separate populations are established the process of speciation continues. However speciation can result even without physical. This is known as sympatric speciation. In this type of speciation, a new species arises while living in the same location with the original species. This is believed to happen when a group of organisms from the species begins to occupy a distinct niche in the environment and eventually become adapted to the conditions while still breeding within themselves to produce a new species. Isolation of gene pool without geographical isolation happens when members of a species in the same geographical location occupy different niches in the same environment. In a similar way, social organisms have controlled mating and hence breeding only happens within the selected group. Species have developed mechanisms to control speciation and breeding. In reproductive isolation, the environment installs external

The Presidents of the United States Movie Review

The Presidents of the United States - Movie Review Example His entry in the office is in a period when the country is facing crisis over the question of expansion of slavery into new western territory. Southern extremists threaten succession if the rule is in favor of the Northern evolutionists. The passing Bills to link California as a free state with slavery measures favorable to the South does not please everyone; including President Taylor. He passes on from an inflation of the intestines (David). In 1991, his descendants gave a green light towards exhuming his body. Forensic analysis reveals no signs of foul play and determines cholera as the likely cause of death. His vice president assumes the presidency. He is Taylor’s opposite and a tool to balance the ticket geographically and politically. He is a Northerner, who aims to please and appease rather than lead. He reverses the policies of his predecessor by signing the compromise of 1850 into law, supporting slavery. He believes its abolishment will give rise to the collapsing of the southern economy; with slavery as an accelerator. He believes the constitution protects slavery issues. He hopes to please everyone for his support for the compromise but fails in 1852 presidential elections (David). A Northern Democrat with strong political ties to the South. He is a social and political butterfly. His election to the presidency is poor timing. He seems to be emotionally unstable after the loss of his only son in a train wreck shortly after his election. He is a troubled man who seeks the approval of others. His vice president William passes within two weeks after the inauguration. He defends slavery as an admitted right to favor Southerners (David). In 1854, he twisted arms to win passage of Kansas-Nebraska act. It repeals the ban on slavery and allows the people to make an informed choice concerning the issues. This result produces much blood shade, and the democrats drop him from the