Death penalty Essay Example | Topics and Well Written Essays - 1250 words

Death penalty - Essay Example According to the research findings it can therefore be said that in a world characterized by all forms of crimes, law and justice are very important aspects in the society. There are different levels of crimes. Some are civil while others are capital. Governments and religious organization dictate the course of justice to the offended and the punishment to the convicted in the society. There are various forms of justice and punishment applied by governments and religious groups. Different crimes require different punishments. Among such punishments is the death penalty. However, in also most all cases the power to prescribe a punishment rests with the courts of law that are arms of the government. Death penalty also known as capital punishment is a governments pre-meditated, and planned lawful infliction of death as a punishment to a legally convicted person. Generally, there is a decreasing tread of death penalty punishments in the recent times. American citizens, political leaders, and religious leaders have been victims of this punishment. Indeed, the numbers are significant. According to Amnesty International, most countries did not use the punishment in 2009. About two-thirds of the countries abolished the death penalty in law or in practice, while 58 countries retained the death penalty in 2009. Consequently, eighteen countries actually carried out executions, killing more than 700 people. However, these figures did not include unreported executions carried out in China. From 1976 to April 2008, execution took place on about 1,099 people in the U.S while those on the death row were 3263. According to Amnesty international, in the year 2008 there were 1718 executions in China were, 346 in Iran, 102 in Saudi Arabia, 37 in United States, 36 in Pakistan, 34 in Iraq, 19 in Vietnam, 17 in Afghanistan, 15 in North Korea and 66 in Japan and other countries. Similarly, by April 1, 2008, 37 states in the U.S were practicing death penalty. To date, the USA, Japan, s ome African states, China, many Asian and Middle Eastern countries retain the death penalty crimes (Amnesty international web). The only conclusion we can make from these statistics is that death penalty is still exists in many countries. Certainly, it is because of its effectiveness in controlling capital offences and rendering justice. The crimes that may lead to a death penalty vary from one country to another and from one religion to another. Same case applies to the methods of carrying out the execution. Some of the crimes that can warrant a death penalty are murder, treason, rape, terrorism, and even adultery in the Muslim religion. Islam law specifically outlines intentional murder, treason, adultery as crimes befitting a death penalty. Generally, in all cases, intentional murder warrants a death penalty. Hanging, stoning, firing squad and beheading are some of the execution methods that Islam recommends. Again, executions take place in public to serve as warnings to would-be criminals. Under the Islam law, enough evidence must be produced against a convict in a due court process for this penalty to be given. Since the early times, there have been debates and opinions in support and against the death penalty. In the United States, there is an equal division in relation to death penalty. Amnesty international condemns the death penalty in all cases regardless of the characteristics of the offender, nature of crime, or the method of execution. According to the Universal Declaration of Human Rights, the penalty is a denial of the right to life. It also quotes that death penalty is a violent practice, and does not accord justice to either the accused or the offended. However, murder is also a violent act, and he who commits it is violent. Thus, it is only fair that he should expect an equally violent punishment like a death penalty. Others argue that it is more expensive to kill a person than to put him in a jail.

The Impact of Education and Political Equality Blacks Have Achieved Essay

The Impact of Education and Political Equality Blacks Have Achieved - Essay Example The essay "The Impact of Education and Political Equality Blacks Have Achieved" discusses the problem of racism in the United States of America that was initially revolved around by slavery. Black slavery in America actually can be traced from the earliest days in America, but most people elect the year 1619 as the real beginning of the institution in what was to become the United States, with the arrival of twenty blacks on a Dutch warship. Slavery in the world was nothing new. There had been slaves in every culture from the dawn of modern man. Slavery is not the issue of this short paper but we had to start somewhere. Racism is really the issue that slavery revolves around and the ethnocentric ideas that one race is just a little better than another race which allows a predisposition towards making one race the master and one the servant. In America, as the servant race, the black population was denied the right to an education that could be used to better their station in life. The main thought being to keep the servant race ignorant and to some degree subservient would make the life of the dominant race all that much better. As the citizens of the world became more enlightened, it was becoming harder and harder to justify excluding the children of the black workers from a good education. The movement toward equality of the races really started in the northern states many years prior to the American Civil War. Blacks in the north were generally treated much differently than in the south.

If I have seen further, it is by standing on the shoulders of giants Essay

If I have seen further, it is by standing on the shoulders of giants - Essay Example Leonardo’s father was one of the traders who traded in Bugia; a Mediterranean port found in North Eastern Algeria. He always accompanied his father on his journeys across North Africa, and through travelling, he gained valuable knowledge of the mathematical systems that were popular in the countries they visited. After travelling for fifteen years, he quit his long travels and went back to his hometown (Robertson & O’Connor, www-history.mcs.st-and.ac.uk). While in Pisa, his hometown; Leonardo decided to write books based on his mathematical foundation. Examples of these books include; Liber Abaci, Practica Geometricae, Flos, Liber Quadratorum, among others. Influences from Indian, Arabian and Greek mathematicians can be detected in his methods. Therefore, it is correct to say that Leonardo’s works represents the developments of results he acquired from his predecessors. Leonardo’s published his first work, Liber Abaci (Book of Abacus), in 1202. The Book of Abacus was based on algebra and calculations that he accumulated during his several voyages. The book introduced the use of Arabic numerals and the Hindu-Arabic place value system into Europe: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 (Robertson & O’Connor, www-history.mcs.st-and.ac.uk). Prior to this time, Roman numerals were being used in Europe, and they were extremely awkward for arithmetic. For example, I =1, V=5, X =10, among others. Leonardo also described in Latin the rules being learnt at elementary schools for subtracting, adding, dividing and multiplying numbers. Several arithmetic problems handled in the book were similar to the ones that appeared in the Arab sources. Liber Abaci’s second section contained several mathematical problems faced by merchants. These problems related to the pricing of goods, how profit calculations were to be conducted, how currencies used in the Mediterranean countries were to be converted, and problems that had originated from China. The third section

The role of trust in strategic alliances Essay Example | Topics and Well Written Essays - 2000 words

The role of trust in strategic alliances - Essay Example Added to this is the input from those who actually involved in this business, giving us a "real world" perspective. This essential input often gives us insider accounts of a contemporary world which we are not normally privileged to see. Before examining the role of trust in Strategic Alliances the notion of Strategic Alliance itself should be descried. In the literature there are different definitions proposed to describe the nature of Strategic Alliances. The first layer of literature (Austin 2000; Lewis 1999) used this term to describe joint ventures which do not involve equity investment by the partners and co-operative activities in areas other than manufacturing. In this case, Strategic Alliances are described as co-operative business activities between two or more firms, entered into for strategic reasons, involving the creation of a separate business entity under joint control and ownership. They can involve equal shareholdings. Strategic Alliances can "involve 'passive' partners who invest money in the operation without taking an active role in its management. alliances are "formed between firms with similar capabilities and capacities usually from industrialised countries; companies involved in strategic alliances are often direct competitors operating in the same product and geographic markets; they are usually entered into for reasons other than market access or the pooling of synergistic resources". While examining the role of trust in Strategic Alliances the research will be based on the second interpretation of the notion strategic alliance. The importance of trust In ordinary day-to-day practice most strategic alliances when making decisions tend to combine these different approaches, although frequently without being aware of the mental processes they are using. It is helpful to be aware of whether one is thinking in terms of 'acts' or 'ends', especially when analysing a dilemma. Theories proposed by Lewicki et al (1998) base a conception of right action on a conception of trust for duty's sake and mainly differ in so far as they specify two different sources of these duties. In order to make the correct moral choices, a strategic alliance simply has to understand what its trust concepts are and what correct rules exist which regulate the duties between the partners. When the parties of a strategic alliance follow their duty, it is behaving morally. When they fail to follow trust policy, it is immoral. It has also been acknowledged that strategic alliances have important obligations to a variety of stakeholders and not just the shareholders, and this should be reflected in their statements of trust (Bleeke, Ernst, 1995). To some extant trust within strategic alliances is based on the codes of ethics or a formal statement of what strategic alliances expects in the way of ethical behavior. It can serve as a guide for employee conduct to help employees determine what behaviors are acceptable. Since the purpose of trust is to let everyone know what is expected and what is

Weigh on Societal Realities Essay Example for Free

Weigh on Societal Realities Essay The movie V for Vendetta gives its viewers an intimate look into the mind of a very creative and ultimately very patient political â€Å"terrorist. † But the question remains, how far-fetched is an idea like this? Could the United States be on its way to such a revolution and if so, is such a revolution really necessary? After having seen this movie a number of times and taking into consideration the current state of our country, I would have to say the answer is yes on both counts. With the recent rash of corporate bailouts and evidence of our government’s involvement in wire tapping, I feel it would be naive and even a bit irresponsible to think our government incapable of causing such an emotional response to take place. While our own media may not completely be controlled by our government, as seemed so obvious in V for Vendetta, a person cannot tune to a news program these days without knowing almost instantly which political party that station sides with. Our foreign enemies have already done a good job of forcing Americans to question their own loyalties, how long before an individual or group takes a broad step to alter our governmental policy? V realized then what so few of us seem to accept now, that a constitution does not necessarily protect us from a government gone awry. Our own history, especially that most recent, has taught us that with enough money and power you can practically get away with murder. Not only can you hold political office, but apparently your means give you the authority to do with it what you will. Of course while vying for this office you’ll stoop to almost any level, tell the most outrageous lies. For example in V for Vendetta, wasn’t it convenient how a cure for this uncontrollable â€Å"plague† was suddenly discovered soon after Sutler took office? And isn’t convenient how all wars will end and all taxes will be eliminated when said favored politician takes control? But nothing really ever seems to work out for the common man; they only seem to work out for those who have the control and the power. Minimum wage may increase, but so does the price of everything else. Those with means, motive and opportunity need only wave their hand or put their signature to paper and their will be done. The average citizen does not have that luxury. The average citizen has but two things to be concerned with, death and taxes, when isn’t their concern supposed to lie with Life, Liberty and the Pursuit of Happiness? While it may be true that not everyone has sacrificed freedom and liberty for sanctity of life, there are many that have and this is just the beginning. Everyday people have to give up on their once noble hopes and dreams merely to make ends meet and give Uncle Sam his fair share. While Congress helps itself to more money and the oil companies are reaping record profits, average hard-working Americans are forced to sell their homes and work two jobs. And it is true that America is the land of dreams, but at what price? The so-called dreams that America stands for are now all but unreachable to the large majority. But the hardship for many Americans does not end with the job or housing market, our own ability to choose and decide for ourselves is also in question. Gay marriage, for example is not recognized in most states, and if politicians had their way the concept would be outlawed altogether. This idea is reflected on a larger scale in V for Vendetta when Valerie recounts the hardships of homosexuals in the intolerant society in which she lived. Gay relationships are not only frowned upon in this society, but having been found to be involved in such a relationship is punishable by death. The United States government may not be acting so rashly now, but who’s to say what the reaction will be when a decision about gay marriage is reached on a national level. Part 2: After seeing V for Vendetta, some may view the character V as nothing more than a terrorist out for blood; a criminal no better than the men who crashed airplanes into our beloved landmarks. However, V represented so much more to so many people; he represented change for the better and a fresh start. What V does in this movie is more than justified, it is necessary. Although he may have been forced to murder some seemingly innocent people, his purpose was always clear; he never faltered. V’s life, his entire existence was a product of a corrupt government, and everyone he crossed paths with was directly involved. He had no name, no history and no identity other than â€Å"patient number five. † It is not until he meets Evey that his life becomes about something more. Evey is connected to V in more ways than he could have at first imagined. Her own parents were â€Å"black-bagged† for being political activists and her brother was a patient at the notorious St. Mary’s. V gains respect for Evey almost instantly and begins to fall in love with her within days of keeping her with him. But even his love for Evey does not transform his ultimate desire to transform a corrupt world. He realizes that it is for people like Evey and he that he put these plans into motion to begin with. By the end of the film V has made an impact on everyone, from average citizen to Sutler himself. He convinces people, as he convinced Evey that a change is inevitable but it could not wait any longer. He called upon people to stand with him and recognize the need for change and bear witness to his revolution. V is not a terrorist because his goal was not to harm innocents and bring about hardship, it is quite the opposite. He is indeed a freedom fighter because freedom is precisely what he was fighting for. He wanted to bring about a better life for his nation’s citizens, much like Robin Hood in a way. He was merely putting the power in the hands of those who should’ve had it all along, hoping in the end they’d know how to use it. I suppose V could be viewed as a martyr because he sacrificed himself for a chance at a new and better age, but I don’t believe martyrdom was his intent at all. Nobody knew his name, where he was from or had ever even seen his face. His actions were for the greater good, not for the purpose of having a monument erected in his visage. While violence may not be the answer, an attitude and a desire like that of V’s is exactly what this country needs. And who knows, it very well may be happening now. V had the wherewithal to wait years for his plans to come to fruition, with only the hope in his heart that they would be fulfilled. Wouldn’t it be wonderful to think that such a soul could be living among us, with such courage of conviction and a will to see change? It is just as V declares to Evey, â€Å"there is no certainty, only the opportunity. † References Wachowski, Andy Larry. (Producers). (2006). V for Vendetta[Motion Picture].

Endosymbiotic Theory of Eukaryotic Cell Development

Endosymbiotic Theory of Eukaryotic Cell Development Abstract The defining feature of eukaryotic cells is that they contain membrane-bound organelles and a true nucleus. The endosymbiotic theory is based upon the idea that eukaryotic cells evolved in steps beginning with the stable incorporation of chemo-organotrophic and phototrophic symbionts from the domain bacteria. This essay reviewed the evidence that supports this theory. After investigating the molecular, physiological and morphological evidence, it is almost certain that chloroplasts and mitochondria are from the domain bacteria, and that many of the genes required for the survival of these organelles are contained within the nuclear DNA of the eukaryotic cell rather than the organelles own independent DNA. It is for this reason that I believe that endosymbiosis was the process whereby eukaryotes began to form and evolve. It was found that the genome of a protozoan, Reclinomonas, contained all the protein-coding found in sequenced mitochondrial genomes, providing support for the specul ative process of endosymbiotic gene transfer. The hydrogen hypothesis seems to be the most likely scenario for the formation of eukaryotes, which explains the need for compartmentalisation with increasing host genome size to improve efficiency of function throughout the cell, and the chimeric nature of eukaryotes. Introduction Based upon data collected from slow decaying radioactive isotopes, Earth is thought to have formed approximately 4.55 billion years ago. From this time of origin, a continual process of geological and physical change has occurred, which created conditions leading to the origin of life about 4 billion years ago. Life is thought to have undergone the process of evolution, defined as DNA sequence change and the inheritance of that change, often under the selective pressures of a changing environment. (1) Microfossil evidence suggests that unicellular eukaryotes arose on Earth approximately 2 billion years ago, after the development of an oxic environment and the invention of respiratory metabolism in cyanobacteria. This timing infers that the availability of oxygen was a large influence on the biological evolution that led to the emergence of Eukarya. (1) The defining characteristic of eukaryotes is the presence of a well-defined nucleus within each cell. (2) Typical eukaryotic cells contain a membrane bound nucleus and organelles enclosed by an outer plasma membrane; these organelles are organised into compartmentalised structures which have their own function(s) within the cell, often working together with other organelles to complete vital biological processes. This compartmentation in cells is essential in organisms as it allows differing compositions of nutrients to exist inside each compartment as opposed to outside, creating perfect conditions for biochemical reactions to occur.(3) The differences between eukaryotes and prokaryotes are shown in Table 1: Mitochondria are membrane-bound organelles found in the cytoplasm of most eukaryotic cells and are most concentrated in cells associated with active processes, such as muscle cells which constantly require energy for muscle contraction. The two surrounding membranes that encompass a mitochondrion differ in function and composition, creating distinct compartments within the organelle. The outer membrane is regular in appearance and composed of proteins and lipids, in roughly equal measure, whilst the outer membrane contains porin proteins rendering it more permeable. The inner membrane is only freely permeable to oxygen, water and carbon dioxide; it contains many infoldings, or cristae, that protrude into the central matrix space, significantly increasing the surface area and giving it an irregular shape. As can be seen in Figure 1, mitochondria contain ribosomes and have their own genetic material, mitochondrial DNA (mtDNA), separate from the nuclear DNA. (4) Mitochondria are the principle sites of ATP production- in a process known as oxidative phosphorylation. Products of the Krebs cycle, NADH + H+ and FADH2, are carried forward to the electron transport chain (ETC) and are oxidised to NAD+ and FAD, releasing hydrogen atoms. These hydrogen atoms split to produce protons and electrons, and the electrons are passed down the ETC between electron carriers, losing energy at each level. This energy is utilised by pumping the protons into the intermembranal space causing an electrochemical gradient between the intermembranal space and the mitochondrial matrix. The protons diffuse down the electrochemical gradient through specific channels on the stalked particles of the cristae, where ATPsynthase located at the stalked particles, supplies electrical potential energy to convert ADP and inorganic phosphate to ATP. In mammalian cells, enzymes in the inner mitochondrial membrane and central matrix space carry out the terminal stages of glucose and fatty acid oxidation in the process of ATP synthesis. Mitochondria also play an important role in the regulation of ionised calcium concentration within cells, largely due to their ability to accumulate substantial amounts of calcium. (3)(5) Chloroplasts are membrane-bound organelles found within photosynthetic eukaryotes. Chloroplasts are surrounded by a double membrane, the outer membrane being regular in appearance whilst the inner membrane contains infoldings to form an interconnected system of disc-shaped sacs named thylakoids. These are often arranged in to stacks called grana. Enclosed within the inner membrane of the chloroplast is a fluid-filled region called the stroma, containing water and the enzymes necessary for the light-independent reactions (the Calvin cycle) in photosynthesis. The thylakoid membrane is the site of the light dependent reactions in photosynthesis, and contains photosynthetic pigments (such as chlorophyll and carotenoids) and electron transport chains. Chloroplasts, like mitochondria, contain ribosomes and their own independent DNA (ctDNA), which is central to the theory of endosymbiosis. The structure of a typical chloroplast is shown by Figure 2: Radiant energy is trapped by photosynthetic pigments and used to excite electrons in order to produce ATP by photophosphorylation. The light dependent reactions occur in the thylakoid membrane (Photosystem II or P680) and ultimately, these reactions produce the ATP and NADPH required for photosynthesis to continue in the stroma (where Photosystem I or P700 is located). A series of light independent reactions occur within the stroma producing carbohydrates from carbon dioxide and water using ATP and NADPH. The most supported hypothesis (put forward by Lynn Margulis) for the origin of the eukaryotic cell is that of endosymbiosis which is suitably named as symbiosis occurs when two different species benefit from living and working together. When one organism actually lives inside the other its called endosymbiosis.'(6) The endosymbiosis hypothesis states that the modern, or organelle-containing eukaryotic cell evolved in steps through the stable incorporation of chemo-organotrophic and phototrophic symbionts from the domain Bacteria. In other words, chloroplasts and mitochondria of modern-day eukaryotes arose from the stable incorporation into a second type of cell of a chemoorganotrophic bacterium, which underwent facultative aerobic respiration, and a cyanobacterium, which carried out oxygenic photosynthesis. The beneficial association between the engulfed prokaryote and eukaryote would have given the eukaryote an advantage over neighbouring cells, and the theory is that the prokaryote and eukaryote lost the ability to live independently. (1) Oxygen was an important factor in endosymbiosis and in the rise of the eukaryotic cell through its production in photosynthesis by the ancestor of the chloroplast and its consumption in energy-producing metabolic processes by the ancestor of the mitochondrion. It is worth noting that eukaryotes underwent rapid evolution, most probably due to their ability to exploit sunlight for energy and the greater yields of energy released by aerobic respiration. Support for the endosymbiosis hypothesis can be found in the physiology and metabolism of mitochondria and chloroplasts, as well as the structure and sequence of their genomes.(1) Similarities between modern-day chloroplasts, mitochondria, and prokaryotes relative to eukaryotes are shown in table 2: Molecular Evidence When Margulis proposed the endosymbiotic theory, she predicted that if the organelles really were prokaryotic symbionts, they would contain their own independent DNA. This was proven to be the case in the 1980s for mitochondria and chloroplasts.(7)Furthermore, mitochondrial DNA (mtDNA) was found to have a proportionally higher ratio of guanine-cytosine base pairs than in eukaryotic nuclear DNA, as found in bacteria. These findings are significant as they strongly suggest that mitochondria and chloroplasts are of prokaryotic origin and nature, supporting the possibility that the eukaryotic cell evolved from the stable incorporation of symbionts from the domain Bacteria. Another striking similarity between mitochondria and bacteria is that they both contain 70S ribosomes and contain a comparable order of genes encoding ribosomal proteins a shown in Figure 4: It is only fair that the molecular problems associated with the endosymbiosis hypothesis that have been put forward are considered. Firstly, mitochondria and chloroplasts can only arise from pre-existing mitochondria and chloroplasts, having lost many essential genes needed for survival. It has been suggested that this is because of the large timespan that the mitochondria/chloroplasts have co-existed. During this time, systems and genes that were no longer needed were either simply deleted or transferred into the host genome. Hence, mitochondria and chloroplasts have lost the ability to live independently over time. This supports the endosymbiotic theory as it provides a reason as to why the ancestors of the chloroplasts and mitochondria were able to survive independently whilst chloroplast and mitochondria are unable to do so now. The study of mitochondrial genomes so far has suggested that mitochondrial genomes actually encode less than 70 of the proteins that mitochondria need to function; most being encoded by the nuclear genome and targeted to mitochondria using protein import machinery that is specific to this organelle.(7) It has been found that the genome of Reclinomonas contains all the protein-coding genes found in all the sequenced mitochondrial genomes: (8) The importance of Figure 5 is that it shows that the mitochondrial genome no longer contains many of the protein-coding genes, and hence, mitochondria are no longer able to live independently. The mitochondrial endosymbiont is believed to have belonged to the proteobacteria since several genes and proteins still encoded by the mitochondrial genome branch in molecular trees among homologues from this group. Interestingly, mitochondrial proteins such as the 60- and 70-kDa heat shock proteins (Hsp60, Hsp70), also branch amongst proteobacterial homologues, but the genes are encoded by the host nuclear genome.(9) This can be explained by a theory called endosymbiotic gene transfer which states that during the course of mitochondrial genome reduction, genes were transferred from the endosymbionts genome to the hosts chromosomes, but the encoded proteins were reimported into the organelle where they originally functioned. (7) This theory is central to the endosymbiotic theory, as it explain s the inability of chloroplasts and mitochondria to live independently even though these organelles are believed to have originated from the domain Bacteria. It is also believed that this gene transfer has provided an essential way in which mitochondrial or chloroplast activity can be regulated. The studies of protists raise  the possibility that mitochondria originated at essentially  the same time as the nuclear component of the eukaryotic cell  rather than in a separate, subsequent event. (10) T This would fit in with the hydrogen hypothesis as described later. A further problem to consider is the extent to which genes were transferred to the cell nucleus. Why did some genes remain in the cytoplasmic organelles? This question has been addressed by the Co-location for  Redox  Regulation (CoRR) hypothesis, which states that the location of  genetic information  in  cytoplasmic  organelles  permits regulation of its expression by the reduction-oxidation  (redox) state of its  gene products. Therefore, evolution by natural selection would have favoured mitochondrial or chloroplast cells that had deleted or transferred some genes to the host genome but had kept those that were still beneficial in the regulation of the organelles activity. (11) Physiological Evidence Evidence for the endosymbiosis theory can be found in the physiology of mitochondria and chloroplasts. For example, both mitochondria and chloroplasts have their own protein-synthesising machinery which closely resembles that of Bacteria rather than that of Eukaryotes. Ribosome function in mitochondria and chloroplasts are inhibited by the same antibiotics that inhibit ribosome function in free-living bacteria. Hence, it is no surprise that both these organelles contain 70S ribosomes typical of prokaryotic cells, and show 16S ribosomal RNA gene sequences, a characteristic of certain Bacteria such as Escherichia coli.(1) For example, human mitochondrial ribosomes can be affected by chloramphenicol (an antibiotic used to inhibit protein synthesis), further evidence that mitochondria are likely to be of bacterial origin. Chloramphenicol is a relatively simple molecule containing a nitrobenzene ring responsible for some of the toxicity problems associated with the drug: Chloramphenicol inhibits protein synthesis due to its high affinity for the large (50S) ribosomal subunit, which when bound to chloramphenicol, blocks the action of peptidyl transferase, preventing peptide bond synthesis. It has also been discovered that chloramphenicol prevents the maturation of the 30S ribosomal subunits, decreasing the number of competent subunits and significantly decreasing the proportion of mitochondrial ribonucleoprotein present as monomers. (12) Also, the antibiotic rifampicin which inhibits the RNA polymerase of Bacteria has been found to inhibit the RNA polymerase within bacteria. Proteins of chloroplast or mitochondrion origin, like bacteria, always use N-formylmethionine as their initiating amino acid of their transcript.(13) Mitochondria replicate, like bacteria, only by the process of binary fission inferring that mitochondria did indeed originate from prokaryotes. The completion of the genome sequence of the cyanobacterium Synechocystis, has provided e vidence for the origin of chloroplast translocation apparatus. Just as the endosymbiosis theory predicts, analysis of this sequence showed that three key translocation components within chloroplasts, Toc75, Tic22 and Tic20, evolved from existing proteins within the cyanobacterial genome.(14)Mitochondria and chloroplasts have remarkably similar mechanisms by which ATP is produced. These ATP-generating pathways often include electron transport chains and proton pumps, similar to that found in prokaryotic energy production mechanisms. One of the most recent problems with the endosymbiosis theory is found within the physiology of mitochondria. Mounting evidence suggests that key components of the mitochondrial transcription and replication apparatus are derived from the T-odd lineage of  bacteriophage  rather than from an ÃŽÂ ±-Proteobacterium, as the endosymbiont hypothesis would predict.'(15) It has been discovered that three of the essential elements of the replication and transcription apparatus; the RNA polymerase, the replicative primase-helicase and the DNA polymerase do not resemble those of eubacteria as predicted by the symbiosis theory, but instead appears to resemble proteins encoded by T-odd bacteriophages. However, this does not disprove the theory of endosymbiosis as it is conceivable that numerous mitochondrial genes were acquired together from an ancestor of T-odd phage early in the formation of the eukaryotic cell, at the time when the mitochondrial symbiont was incorporated. (15) Morphological Evidence Another characteristic that further supports the hypothesis is that mitochondria and chloroplasts contain small amounts of DNA that is different from that of the cell nucleus which is arranged in a covalently closed, circular structure, with no associated histones, typical of Bacteria. Mitochondria are surrounded by two membranes, separated by the inter-membranal space and each with a different composition. Mitochondrial membranes more closely resemble membranes found in Gram-negative bacteria in terms of lipid composition than eukaryotic membranes. (16) The inner-membrane infoldings in the mitochondria lends more credibility to the endosymbiosis theory as the cristae are adaptations that increase the surface area of oxidative enzymes, evolutionary analogues to the mesosomal membranes of many prokaryotes (16)Further evidence that mitochondria and chloroplasts are of a prokaryotic origin is the lack of cholesterol in their membranes. This is significant because it is an essential stru ctural component in many eukaryotic membranes, mainly in mammalian cell membrane, but it almost completely absent amongst prokaryotes. Another problem is that recent genetic analysis of small eukaryotes that lack many characteristics that are associated with eukaryotic cells, most importantly mitochondria, show that they all still retain genes involved in the synthesis of mitochondrial proteins. In 1983, the taxon Archezoa was proposed to unite this group of odd eukaryotes, and the belief was that these cells had diverged from other eukaryotes before these characteristics evolved and hence represented primitive eukaryotic lineages. Before the recent genetic breakthrough that shows that these eukaryotes contain genes involved in mitochondrial protein synthesis, molecular work supported their primitive status, as they consistently fell deep into the branches of eukaryotic trees. This recent genetic analysis implies that all these eukaryotes once had mitochondria, suggesting that they evolved after the mitochondrial symbiosis. There is also the question of how the eukaryotic cell arose, including the nature and propert ies of the cell that acquired mitochondria and later chloroplasts, and how the nuclear membrane was formed which touches upon the compatmentalisation within cells and its importance in the functioning of the eukaryotic cell. (7) Formation of the eukaryotic cell There have been two hypotheses put forward to explain how the eukaryotic cell arose. One states that eukaryotes started as a nucleus-bearing lineage that later acquired the bacterial ancestor of the mitochondrion and the cyanobacterial ancestor of the chloroplast by the process of endosymbiosis. This nucleated line then diverged into the lineages giving rise to animals and plants. It is thought that the nucleus arose spontaneously in an early cell. One possible cause for the spontaneous formation of the nucleus is that it arose in response to the increasing genome size of early eukaryotes. (1) The second hypothesis, also known as the hydrogen hypothesis, states that the bacterial ancestor of the mitochondrion was taken up by a member of the Archaea via endosymbiosis, and from this association, the nucleus later emerged, followed by a later acquisition of the cyanobacterial ancestor of the chloroplast. The main difference between these two hypotheses is the position of the mitochondrion relative to the formation of the nucleus in time and hence on the universal phylogenetic tree. The hydrogen hypothesis put forward by William F. Martin and Miklos Muller in 1998, proposes that the eukaryotic cell arose from a symbiotic association of an anaerobic, hydrogen dependent, autotrophic archaebacterium (the host) with a hydrogen producing, oxygen consuming eubacterium (the symbiont), which released molecular hydrogen as a waste product of anaerobic heterotrophic metabolism. (17) The dependence of the host upon the molecular hydrogen as an energy source, produced as a waste product b y the symbiont is thought to be what lead to the association. In this scenario, the nucleus arose following the formation of this stable association between these two kinds of cells, and genes involved in lipid synthesis were transferred from the symbiont to the host chromosome. This may have lead to the synthesis of bacterial (symbiont) lipids by the host, eventually leading to the creation of an internal membrane system, the endoplasmic reticulum and the early stages of a eukaryotic nucleus. As the size of the host genome increased with time, changes were made to maximise the efficiency of replication and gene expression via the process of evolution. Hence, over time, this kind of cell compartmentalised and sequestered the genetic coding information within a protected membrane away from the cytoplasm. The formation of a mitochondrion-containing nucleated cell line was complete, which then later acquired chloroplasts by endosymbiosis. The hydrogen hypothesis has explains the observ ation that eukaryotes are of chimeric nature, containing attributes of both Bacteria and Archaea. (1) Conclusions In summary, molecular, physiological and morphological evidence can be found to support the endosymbiosis theory put forward by Lynn Margulis. Most compelling of which is the numerous similarities between organelles such as chloroplasts and mitochondria with prokaryotes, coupled with the inability of the organelles to live independently despite having their own independent DNA due to most of the genes required for the survival of the organelle being stored in the nuclear DNA of the host. The importance of this should not be underestimated, as it does all but prove that the ancestors of mitochondria and chloroplasts were of a prokaryotic origin and thus were once able to live independently. Therefore, this does lend credibility to the endosymbiosis theory as the symbionts that were allegedly incorporated were likely to have been from the domain bacteria, and that something must have occurred which stopped the symbionts being able to live independently, an event which many scientists n ow believe to be the process of endosymbiotic gene transfer. The hydrogen hypothesis appears to be the likely scenario for how the eukaryotic cell evolved, as it explains the formation of the nucleus as being a response to the growing size of the nuclear genome of the host, which would have maximised efficiency of gene expression. Endosymbiosis also explains why the eukaryotic cell appears to be of a chimeric nature; containing attributes of Archaea (e.g. similar transcription and translation apparatus) and Bacteria (e.g. contain same type of lipids).

Videogames Don?t Kill People, People Kill People Essay -- essays resea

Videogames Don’t Kill People, People Kill People Every generation has pointed a finger at the recreational pastimes of young persons, accusing that these activities lead our nations youth astray and induce violent or antisocial behavior. Novels, music, TV, movies, and now the finger is pointing straight at one of the newest and quickest growing youth pastimes; videogames. This particular pastime differs from others in their reality and scope for direct participation, therefore allowing the crusty old curmudgeons to conclude that playing them leads all young people to commit acts of violence.   Ã‚  Ã‚  Ã‚  Ã‚  Numerous studies have been conducted to determine whether or not there is a direct link between violent tendencies and videogames. Some tests claim there is a definite link, others refute it, but both often show very shaky statistics. Most tests simply prove inconclusive. According to an article by Anne D. Walling, a recent study by Drs Bensley and Van Eenwyk shows that: Rates of adolescent violence, homicide, weapon carrying, and other markers of antisocial behavior fell consistently during the period when violent videogames became ubiquitous, more graphic, and more realistic. (1) This would suggest that youths are using videogames as a form of escape. Instead of being out on the streets committing acts of delinquency, they are instead at home, safely playing videogames.   Ã‚  Ã‚  Ã‚  Ã‚  Walling also provides the combined results from twenty-nine other individual studies of this topic. The studies all varied greatly in design and quality, preventing any firm determination from being reached. Children of middle school age and younger showed no association between videogames and aggression in girls, and both increases and decreases in aggression among boys. Studies of high school students predominately dealt with boys, often using self-report. Both calming and arousing effects were again reported, and no consistent relationship was drawn between violent games and actual behavior. In college students and young adults, results were yet again mixed, but calming effects were more common, particularly if the prior mood was hostile or aggressive (2).   Ã‚  Ã‚  Ã‚  Ã‚  So-called experts like to point their fingers at Eric Harris as an example that violent videogames do indeed create violent children. Harris was one of the t... ...n that there seems to be no direct link to violent behavior and playing violent videogames. Studies even show that adolescent crime has decreased as videogames have become more realistic and graphic, showing that they seem to have a more calming effect on kids. As long as people can continue to differentiate between what’s real and what’s not, we should be just fine. However, as long as there are crusty old curmudgeons out there who are afraid of things they don’t understand, then videogames will always be under heavy fire. Works Cited Ahmed, Shahed. â€Å"Further Investigation of Violence and Gaming.† Gamespot. 6 August 2000. 8 April 2003 . â€Å"The Games Kids Play: Are Mature Video Games Too Violent for Teens?† Current Events 7 February 2003: 3. Grossman, Lev. â€Å"Busjacking for Grownups.† Time November 2002: 80-81. Satterfield, Shane. â€Å"IGDA Holds Game Violence Summit.† Gamespot. 8 January 2001. 8 April 2003. . Varanini, Giancarlo. â€Å"Violent Media May not be to Blame.† Gamespot. 8 February 2001. 8 April 2003. . â€Å"Violence is A-Ok.† Electronic Gaming Monthly August 2002: 13. Walling, Anne D. â€Å"Do Video Games Lead to Violent Behavior in Children?† American Family Physician 65 (2002): 1436-1437.