Theory of Endosymbiosis Essay Example | Topics and Well Written Essays - 1000 words

Theory of Endosymbiosis - Essay Example As they became more interdependent an obligatory symbiosis evolved." (Margulis, Live Chat, n.p.) The Theory of Endosymbiosis also states that eukaryotic undulipodia originated from spirochete bacteria. The term "undulipodia" is used to describe the eukaryotic motility organelles, flagella and cilia. Undulipodia are composed of microtubules in a specific configuration. Microtubules are comprised of several closely related proteins called tubulins. These structures are far larger and more complex than bacterial flagella, which are made of flagellin proteins. The Endosymbiosis Theory postulates that undulipodia may be derived from bacteria through motility symbioses. This idea is referred to as the exogenous hypothesis. The series of explanations that lead up to the detailed elaboration of the endobiotic origins of the flagellum and cilia point to several lines of circumstantial evidence. The argument emphasizes the biology of the organelles themselves, their distribution, and the occurrence of related and analogous structures. The Theory of Endosymbiosis significantly stimulated a variety of analytic approaches to the problem of organelle origins. Support for the endobiotic origin of mitochondria and chloroplast is very strong. Margulis included in her theory the proposition that the eukaryotic flagellum evolved from an endosymbiotic spirochete like prokaryote that became part of its eukaryotic protistan host. The major line of information in this regard has come from her studies of an unusual group of spirochetes that live on and in protists. These spiral bacteria depend for their locomotion on bundles of typical bacterial flagella, but some also have microtubules, which are not found in other prokaryotes but are ubiquitous in eukaryotic cells.(Avers, 124) There is a substantial amount of evidence within the theory itself to suggest that such a postulation of evolution of the eukaryotic cell is correct, with regard to the origins of mitochondria and chloroplasts. Much of this evidence is based on the differing features of the two types of cells, and similarities between mitochondria and chloroplasts and present day prokaryotes, the bacteria. The considerable substantiations, as elaborated above seem to indicate that the theory of serial endosymbiosis is correct. One such fact is that previously non-existing mitochondria or chloroplasts, if required to be freshly produced, cannot be synthesized in the body without the presence of an original organelle. The reason for this is that the nucleus inside the cell, which contains the genetic code for the rest of the cell, encoded onto DNA molecules, does not contain sufficient coding to account for all of the proteins present in the organelles. There are some proteins present in the organelles which are missing altogether in the DNA code of the nucleus and there are some which differ slightly from those present inside the nucleus. The "missing" DNA is accounted for by the loop of DNA present inside the organelle. This DNA is of the same form as is present in all prokaryotic cells. That is, the DNA is circular, and it lies free in the "cytoplasm" of the

Research proposal ( research for social and community development) Essay

Research proposal ( research for social and community development) - Essay Example However, a study conducted by Crosby and Holtgrave (2006) reveals that low income and poverty while significantly linked to teenage pregnancy, social capital had a stronger influence on teenage pregnancy. Therefore, the role of social and community development appears to have a significant link to teenage pregnancy in the UK and should form the basis of further research. The proposed study will be conducted using a mixed methods research in that both qualitative and quantitative data will be collected and analysed. The qualitative data consists of 5 interviews and the quantitative data consist of at least 50 surveys. The sample population will consist of mothers who were pregnant as teens. Social capital theory will be used as a conceptual framework for analysing the data collected. This section should include the material which outlines the rationale for the project, i.e. why this study needs to be done. This should be done in a way that is both accessible and scholarly, i.e. have proper cited sources. This study is important because the UK is second only to the US in teenage pregnancy rates among all developed nations (Kmietowicz, 2002). Meanwhile the UK has the largest teenage pregnancy rates in all of Europe (Kmietowicz, 2002). Teenage pregnancy is regarded as an important social issue for a number of reasons. The main reason teenage pregnancy is perceived as an important issue is the risk of health to the pregnant teen who seeks to hide the pregnancy or terminate the pregnancy or who engages in risky behaviour that subjects the foetus to the risk of harm (Bonell, 2004). Other facts attributable to the characterization of teenage pregnancy as a major social problem is the welfare services required to support the teen mother and the infant once born (Bonell, 2004). Teenage pregnancy is also said to interfere with the teen mother’s education and thus employment