Theories Regarding The Latitudinal Diversity Gradient Biology Essay

Theories Regarding The Latitudinal Diversity Gradient Biology Essay Aim Different publications theories regarding the latitudinal diversity gradient were examined and analysed to attempt to show how theories explaining the latitudinal diversity gradient have changed in the period 1980-2010. Method In total, six main theories were identified from the literature and resources studied by searching abstracts and articles for relevant key words. Main Conclusions The main conclusion drawn was that no single theory can adequately explain the latitudinal diversity gradient. Species diversity is ultimately controlled by a combination of factors and until there is conclusive proof or agreement on this subject biogeographers and biologists will continue to hypothesize on the matter of the driving factors behind the latitudinal diversity gradient. Key Words Latitudinal Diversity Gradient, Geographical, Species, Species Richness, Taxa, Hypothesis, Biotic, Historical Perturbation, Climate Stability, Climate Harshness, Mid-Domain, Evolutionary Rate, Evolution. Introduction The latitudinal diversity gradient is the term used to describe the decrease in species richness as one moves away from the equator. [1] Discovered by Alexander von Humboldt in 1799, it has remained one of the key questions in Evolutionary Ecology. Understanding the latitudinal diversity gradient is essential in our understanding of the spread of invasive species, disease and more pertinently, the effects of global climate change (Bradford et al 2006) Hillebrand (2004) identified that this subject has received great attention but the majority of studies have concentrated on only one or a small number of organisms. An example of this being Krebs (1985) who examined snake and ant species throughout America. In the past 30 years there have been many different theories that attempt to explain the latitudinal diversity gradient, from further reading into each individual theory it became apparent that no individual theory is entirely self supporting, rather a combination of each is perhaps the best way to try and answer the question of what is the driving factor behind the latitudinal diversity gradient. Theories Species-Energy The species-energy theorem centres on the hypothesis that it is the amount of available energy that governs the potential species richness of the system. Fraser and Currie examined this hypothesis in their 1995 paper The Species Richness-Energy Hypothesis in a System Where Historical Factors are Thought to Prevail: Coral Reefs. They found that the best environmental predictors of diversity were temperature and biomass and also that there was little supporting evidence for other hypotheses such as environmental stability. Turner et al (1987) found that the diversity of butterflies, measured as the number of species is highly correlated with sunshine and temperature during May to September, with these two variables accounting for nearly 80% of the variance in diversity. Mid-Domain Effect Originally proposed by Colwell and Hurtt, (1994) this hypothesis works on the basis that it is geographical constraints that contribute to species richness. Colwell et al (2004) state that if species ranges are shuffled randomly within a bounded geographical domain free of environmental gradients, ranges overlap increasingly toward the centre of the domain, creating a mid domain peak of species richness. There is still debate over whether or not the Mid Domain Effect is responsible for the latitudinal diversity gradient as empirical support for it is often weak. Zapata et al (2005) Effective Evolutionary Time Effective evolutionary time hypothesizes that it is evolutionary time and the factors associated with it, such as environmental energy, mutation, generations and selection that are responsible for the diversity gradient. Rhode (1992) Climate Harshness and Climate Stability The Climate Harshness theory speculates that fewer species are found at high latitudes due to their inability to cope with the pressures that the environment places upon them. Climate Stability proposes that the reason for the diversity gradient is due to species specializing into narrower and narrower niches due to stable climate conditions, resulting in increased speciation and therefore resulting in temperate areas at high latitude having a low diversity as they experience more changeable weather events throughout the year. Climate stability is even observed in marine environments with strong latitudinal gradients being observed. Kaustuv et al (1999) as well as in terrestrial environments. Lima-Ribeiro et al (2009). Evolutionary Rate Cardillo et al (2005) argue that the increased diversity observed at lower latitudes is due to high evolutionary rates resulting in increased speciation. Mettelbach et al (2007) found that there was evidence for higher rates of diversification in the tropics, with studies of latitudinal variation suggesting greater speciation at lower latitudes. The results from these studies show that there is indeed a link between low latitudes and evolutionary rate resulting in increased speciation. Discussion Since the 1980s there have been suggestions of new theories and re examinations of others, for example Zapata et al (2005) re examine the mid domain effect and address its criticisms. Each of the individual theories discussed earlier proposes its own explanation for the latitudinal diversity gradient. Some hypotheses are circular and some are founded on insufficient evidence, Rhode (1992). In the past 30 years theories purporting to explain the latitudinal diversity gradient have changed from supporting one viewpoint as the sole cause of the latitudinal diversity gradient to being more inclusive of other hypotheses, the Evolutionary time theory is the most inclusive of other theories as it recognises that no single factor can be the cause of such a complex system. References and Literature Cited 1. On-Line Biology Book, L, Latitudinal diversity gradient http://mac122.icu.ac.jp/biobk/BioBookglossL.html Accessed on 17-08-2010 Hawkins, B.A, Diniz-Filho, J.A.F, Jaramillo, C.A., Soeller, S.A., 2006. Post-Eocene climate change, niche conservatism, and the latitudinal diversity gradient of New World birds. Journal of Biogeography. Cardillo, M. Orme, C. D. L., Owens, I.P.F. 2005. Testing for Latitudinal Bias in Diversification Rates: An Example Using New World Birds. Ecology. Colwell, R.K. Hurtt, G.C 1994. Nonbiological Gradients in Species Richness and a Spurious Rapoport Effect. The American Naturalist, Vol. 144, No. 4 October 1994 Colwell, R,K. Rahbeck,C. Gotelli, N,J. 2004 The Mid-Domain Effect and Species Richness Patters: What have we learned so far? Vol. 163. No.3 March 2004 Fraser, R.H, Currie, D.J. 1995. The Species Richness-Energy Hypothesis in a System Where Historical Factors are Thought to Prevail: Coral Reefs. The American Naturalist Vol.148, No. 1 July 1996 Hillebrand, H. 2004. On the Generality of the Latitudinal Diversity Gradient. The American Naturalist, Vol 163, No. 2. 2004. Kaustuv, R., Jablonski, D., Valentine, J. W. 1999. Dissecting Latitudinal Diversity Gradients: functional groups and clades of marine bivalves. The Royal Society Krebs, C.J.1985. Ecology. The Experimental Analysis of Distribution and Abundance. Third edition. HarperRow, New York. Lima-Ribeiro, M., Diniz-Filho, J. A. F., Barberi, M. 2010. Climate Stability and the Current Patterns of Terrestrial Vertebrate Species Richness on the Brazilian Cerrado. Quaternary International, Volume 222, Issue 1-2. August 2010 Mittelbach, G. G., Schemske, D. W., Cornell, H. V., Allen, A. P., Brown, J. M., Bush, M. B., Harrison, S. P., Hurlbert, A. H., Knowlton, N., Lessios, H. A., McCain, C. M., McCune, A. R., McDade, L. A., McPeek, M. A., Near, T. J., Price, T. D., Ricklefs, R. E., Roy, K., Sax, D. F., Schluter, D., Sobel, J. M. and Turelli, M. 2007. Evolution and the latitudinal diversity gradient: speciation, extinction and biogeography. Ecology Letters Rhode, K. 1992. Latitudinal Gradients in Species Diversity: The search for the primary cause. Oikos. Vol. 65, No. 3. December 1992 Turner, J.R.G. Gatehouse, C.M and Corey, C.A. 1987. Does Solar Energy Control Organic Diversity? Butterflies, Moths and the British Climate. Oikos, Vol. 48. No.2 Zapata, F.A., Gaston, K. J., Chown, S. L. 2005 The Mid-Domain Effect Revisited. The American Naturalist, Vol. 166, No. 5 November 2005.

Lawsuit In Movies

The movie North Country featured Josey Aimes, the woman with two kids who only wanted to make life better and happier for her family. After leaving her abusive husband, she found a job as hairdresser. But learning that working in the local mine could pay her good enough, she applied for it not knowing the prejudices and negations received by women miners. As days passed by in her life as a miner, she started to notice the dominance of the clan of Adam in that part of the country. Everyday, she could hear sexist jokes, and disrespectful comments from male coworkers, she began to outrage turning herself the object of hate, but at the same time, of lust. She later found out that the women in her hometown were so scared to come out of their shell†¦ that nobody even wanted to stand by her side. With the help of a local lawyer, she filed for a sexual harassment case against her workplace, when she was nearly raped. The movie opened with a big bang of emotions and scenarios that continuously built the excitement of any viewer to follow the journeys and decisions made by the female protagonist. Events like going away from her husband, getting inside the manly world of mining, and being the herculean woman amidst the fangs and stings of men, kept true to the philosophy of Niki Caro – women empowerment, like the Whale Rider. The director was able to present the powerhouse impact of the scenes attributed to a community enveloped in discrimination against women. Charlize Theron played the protagonist woman and added merits to her credentials. North Country was based on the case filed and won by Lois Jensen against the Eveleth Mines. It took over two decades before the charge was settled. Indeed, she made history by changing the course of sexual harassment law in the United States of America. The lawsuit created rooms for the rights of women against sexual harassment, discrimination and other negative actions towards women in the workplace. Erin Brokovich With three children to give a decent life, she asked her lawyer to help her get a work. She later found her career in researching about the case of water pollution and sickness among the children in a small town. She then excavated that the cause was the toxic wastes dumped by the huge company in the area. The worse part was that the company was trying to hide it from investigations. The company was so powerful that it could just make her dead in the records, but she was not stopped by this. She went an extra mile just to expose the truth. But she is not your ordinary good girl, smart employee in the office. She had skeletons in her closets, too. She usually left her children with her biker boyfriend, acting like she was not the mother. Dressed like a whore, she made Erin Brokovich heroine in a small town when she brought down a deep-pocketed company. Steven Soderbergh directed this film with wit and passion. He maximized the potentials, including the natural sexiness, of Julia Roberts, who played the role so effectively in return. This might have driven the female part of the audience crazy of desiring to be like Erin in their worlds. Every woman wanted to be the new modern woman, dressing casually but could carry the world when asked to. This is like a refresher movie of what Roberts was in the Pretty Woman, the role that made her the highest-paid and the most sought-after actress in Hollywood. The movie was based on the story of Erin Brokovich who helped the burdened community win over the Pacific Gas & Electric Company. She did not have the looks or appearance of a lawyer. But she managed to go on her way to help in the success of the largest settlement for a direct lawsuit ever. This clearly shows that if you have done something bad, it will haunt you no matter where you are and what status you belong. Moreover, no matter how good you are in hiding or covering your wrongdoings, the issue itself could find itself in the surface. A Civil Action A community struck with something that made the people vulnerable to skin rashes, and a leukemia outbreak among the youth, was finally put to limelight when they start to take their fate against two big corporations. The residents wanted someone to apologize for the death of their children. Their need for someone to defend them came at the right time for the firm of Jan Schlichtmann, who chose cases they believe they could get to success. Usually, their clients were poor, putting a pro-people and pro-justice on their image. But in his mind and heart, the lawyer was hoping for large settlement money. As they were getting through the lawsuit, the firm was also continuously sinking below the line of bankruptcy. The movie was based on the primary accounts of Jonathan Harr during the proceedings. This embedded the movie inside the courtroom. Stories about the Woburn victims were set aside for the presentation of what really happened inside the hearing of the case. John Travolta gave justice to the character of Schlichtmann, as being the ambitious lawyer, who wanted to nail down WR & Grace and Beatrice Foods, for a substantial amount of money. He also made a mistake when he was carried with the story of one of the victims. Robert Duvall, who played the antagonist Jerome Facher, also made a great effort in his role as the lawyer of one of the companies involved in the issue. Environmental crime is probably one of the celebrated cases in the history of man. This is because different sectors participate in the deliberation of points, trying to sound pro-environment. Oftentimes, big industrial companies are usually the subjects. Justice has its price, goes the tagline of the movie that peeked through the climax of the movie wherein the victims got a whopping amount of settlement money. This shows the negative attachments of the judicial system of the country. It made clear that money could have the power to break the shield of morality, humanity, and most of all, love. Reference: Caro, N (dir). 2005. North Country. USA: Warner Bros. Pictures. Soderbergh, S (dir). 2000. Erin Brokovich. USA: Jersey Films. Zaillian, S (dir). 1998. A Civil Action. USA: Touchstone Pictures.      

The Fundamentals of College Admission Essay Revealed

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The War On Gun Control - 1296 Words

Jason Edwards English 3 08 May 2015 The War on Gun Control The debate over gun control is one of the most heated debates currently going on in the government, and in the general population of the United States. One side of the debate says that guns are a legal right protected by the Second Amendment, and help to keep citizens safe if they are ever attacked. The other side says that guns are an evil thing, that they are the cause of death and destruction, and they want to infringe on American s rights, and basically negate the entire second amendment. Gun Control is something that would really hurt this nation. If guns are banned, law abiding citizens will turn in their guns, and criminals will be free to do whatever they want without the fear of a citizen having a gun to stop them. Pro Gun control advocates are under the impression that if guns are banned, the violent crime rate will go down exponentially. As some of you may know, the United Kingdom has a 100% gun ban. Rifles, Pistols, Shotguns, everything. The Police don t even carry guns over there! A wordpress article by Steven Goddard compares the violent crime rates in the United States, and the United Kingdom. This is what he found. â€Å"According to the FBI, there were 1.2 million violent crimes committed in the US during 2011.According to the UK government, there were 1.94 million violent crimes in the UK during 2011.† This already sounds bad enough for the people tryingShow MoreRelatedThe War on Gun Control Essay957 Words   |  4 Pages Gun Control War We are no stranger to gun control debate and controversy here in the U.S. We hear of gun deaths, mass and school shootings on the news on a daily basis. Is it safe to say that the U.S. needs permanent gun control laws to protect its citizens or would it be in violation the constitution? The second amendment was written by our founding fathers back in 1791 in a day where it was common for any citizen to own a weapon. 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