Wednesday, March 11, 2020

Identification of Gram negative bacteria using biochemical tests, including API The WritePass Journal

Identification of Gram negative bacteria using biochemical tests, including API Abstract Identification of Gram negative bacteria using biochemical tests, including API AbstractIntroductionMethodConclusionReferencesRelated Abstract Four pure, unidentified cultures of (gram positive cocci) bacteria, labelled A-D were cultured on various agar media. Also an API test was simulated to identify another unidentified bacterium. Identification of bacteria is important when choosing an effective treatment for a microbial-causing illness. This experiment focused on the cultural and biochemical characteristics of bacteria in aid of identification. Under aseptic conditions, each of the four unidentified bacterium were cultured using the bile aesculin, manitol salt and the blood agar plates provided. These were then incubated for over a week and then observed. A catalase and Voges-proskauer were also carried out to verify the identity of the 4 strains of bacteria. Bacteria that produced air bubbles in the catalase test (as oxygen is one of the products formed, in the presence of the enzyme catalase) and a red colour change for the Voges-proskauer (bacteria is able to produce a compound called acetylmethylcarbinol), both ind icative of a positive result. For simplicity, the end cultures were compared with a table of results provided in the experiment to confirm the identity of Enterococcus faecalis, Micrococcus luteus, Staphylococcus aureus and Streptococcus pyogenes bacteria. The first culture easily identified as Streptococcus pyogenes   produced a visible ÃŽ ²-haemolysis on blood agar; with an obvious clear zone around the colonies and was also unable to grow on manitol salt agar. The other strains were then determined from the various biochemical tests, as all bacterium possess particular characteristics that distinguish them from other genera. The bacterium used in the API was identified as Staphlyococcus. aureus, by use of an identification table, provided by the manufacturer of the API. However in a normal setting various other tests would have to be conducted to conclude the genus and species of the bacteria. Introduction Gram positive and gram negative bacteria have a rigid cell wall called peptidoglycan and this can be used to distinguish between the two groups. Gram positive bacteria have a very thick outer layer of peptidoglycan. They also have the lipopolysaccharide layer absent. (Madigan et al., 2009) Gram positive bacteria usually appear purple and gram negative bacteria can be red to pink in colour with the use of gram staining. (Madigan et al., 2009) Once established the fact that the bacterium belong to gram positive group, the Dichotomous Key of Gram Positive bacteria can be used to differentiate bacteria by use of various biochemical tests. (Willey et al. 2008) The isolation and identification of bacteria is an essential diagnostic tool in microbiology, especially investigating pathogenic bacteria that cause infectious diseases. The clinician and microbiologist work together in this identification process. (Willey et al. 2008) Samples from the suspected infected area of a patient can be extracted and grown aseptically on agar medium to avoid contamination; these mixed cultures are then separated to produce single colonies of a genus bacterium. The shape of the bacteria can be determined by microscopy (using gram staining or other staining techniques for acid-fast bacteria), and culturing of the bacteria on various media – selective, differential and certain characteristic (metabolic) media. (Willey et al. 2008) Selective media only allow certain bacteria to grow, whilst differential media are used to distinguish bacteria from others, in the presence of some form of dye or indicator. (Madigan et al., 2009)   It is also important to note the conditions bacteria are able to grow in, as some may tolerate the presence of oxygen (aerobes) whilst others will not (anaerobes). The presence of specific enzymes enables aerobic bacteria to grow, whilst anaerobic bacteria cannot. (Madigan et al., 2009)   Voges-Proskauer tests distinguish bacteria that are able to produce fermentation, especially when they cannot respire aerobically. (Willey et al. 2008) When microscopy and culturing methods alone are not adequate enough to identify a species, specific biochemical tests are carried out. These tests are used to eliminate the number of possible pathogens causing the illness in question; by comparing the unidentified pathogen with the known metabolic characteristics stored on computer databases. (Madigan et al., 2009) These may include testing for products the bacterium may produce (due to a presence of specific enzyme/s) or even their ability to grow on either selective or differential media or a combination of the two. However some require further investigative tests to identify the bacteria. (Madigan et al., 2009)  Ã‚   An example is the coagulase test, which differentiates S.aureus from S.epidermidis, coagulase has the ability to clot plasma. (Willey et al. 2008)   Once the bacteria have been identified, antibiotic sensitivity tests (susceptibility tests) may be performed in order to determine which antibiotic/s would be most ef fective in treating the illness related to the microorganism. (Willey et al. 2008) The ability of bacteria to produce catalase is an important biochemical characteristic, aerobic bacteria are able to secrete specific enzymes this characteristic can be manipulated in identification. (Madigan et al., 2009)   Aerobic bacteria are able to neutralise hydrogen peroxide (that would otherwise be toxic to it) by converting it to water and oxygen. Bubble formation would indicate a positive result of this reaction taking place. (Greenwood et al., 2007) This test helps to identify streptococcus from staphylococcus. (Willey et al. 2008) Further more some bacteria may have the ability of secreting other enzymes like superoxide dismutase and peroxidise. This depends on the growth conditions the bacteria require, to neutralise free (unpaired) oxygen radicals that would otherwise destroy the normal functioning of bacterial cells. These radicals are the result of oxygen being reduced in the electron transport chain.   (Willey et al., 2008) Indicator medium of blood agar (usually containing horse blood) is used for the haemolysis test to indicate if the bacterium produces a specific toxin (haemolysin) this is a common virulence factor that pathogenic bacteria possess. A positive result indicates the bacterium possesses this toxin. (Willey et al. 2008)   The toxin is able to lyse erythrocytes by forming pores in the cell surface, releasing its contents – haemoglobin and other ions. (Willey et al., 2008) This can be observed on blood-agar as a clear halo with no distinct colour around the colonies, called ÃŽ ²-haemolysis. Partial (ÃŽ ±) haemolysis leaves a slight green discolouration, as hydrogen peroxide oxidises haemoglobin to methaemoglobin. (Greenwood et al., 2007) Bile aesculin agar is selective and differential, black formation on the culture plate would indicate the ability of the bacterium to hydrolyse aesculin and mix with ferric citrate. (Mahon and Manuselis, 2000) The manitol salt agar is an example of selective media that only allows growth of specific bacteria to grow, thus it can be used in biochemical tests. This is due to the high concentration of salt within this medium, which inhibits most bacteria from growing. (Mahon and Manuselis, 2000) Rapid identification of a microorganism can be determined by the use of an API (Analytical Profile Index) or manual ‘kit’ (Willey et al. 2008)  Ã‚   that contains 20 microtubules with dehydrated substrates, once inoculated with bacteria and left to incubate; the various wells produce colour changes when reagents are added. These colour changes are related to the metabolic characteristics of specific bacteria that can be matched to an identification table. The use of current technology enables one to study the genomic and antigenic structure of microorganisms and is thus useful in identification. The use of PCR and electrophoresis can be used in Multilocus Sequence Typing (MLST) and genomic fingerprinting. (Willey et al. 2008)  Ã‚   Also the various surface proteins especially antigens can be identified for its interaction with particular antibodies by immunofluorescence or agglutination technique. This technique may yield rapid results and streptococci associated with sore throats can be identified this way; however these tests are not as accurate as the culturing techniques. (Champoux et al., 2004) New and more accurate technologies are being studied such as the use of Biosensors. (Willey et al., 2008) Staphylococci have a round shape (from the Greek word ‘kokkos’ meaning a berry.) these bacteria form clusters like grapes (derived from the Greek word ‘staphule’) Staphylococci also have a slime layer, and are mainly found on the surface of skin.(Heritage et al., 1999) These aerotolerant anaerobe are able to grow in either aerobic or anaerobic conditions. Although Staphylococcus aureus is harmless living on the surface of the skin, it is able to cause serious illness like septicaemia when it enters open wounds. (Mandal et al., 1996) This bacterium can also become an opportunistic pathogen, responsible for epidemics like MRSA due to resistance of the antibiotic methicillin and emerging resistance to vancomycin. (Willey et al., 2008) A quick biochemical test called Staphaurex can also be used. (Willey et al., 2008) Streptococci are facultative anaerobes and do not form any gas products, as they produce lactic acid fermentation and will therefore catalase negative. (Willey et al., 2008)   The streptococcus genera cover an extensive group of bacteria – the cocci that are spherical in shape and thus placed into 3 groups: pyogenic, oral and other (colon) streptococci. (Greenwood et al., 2007)   Virulence factors produced by the pathogenic bacteria (pyogenic) like the presence of streptolysin, have the ability to lyse erythrocytes and can inhibit the host’s immune response as it kills leukocytes. Haemolysis is a key step to identify pyogenic (harmful) streptococci from other streptococci. (Willey et al., 2008) The species E. faecalis can be found in the intestinal tract, it has the ability to cause opportunistic infections like urinary tract infections (UTI) and also is able to grow in 6.5% sodium chloride, and can resist certain antibiotics. (Willey et al., 2008)   The enterococcus group are closely related to the streptococcus group, but are associated more within the intestinal area. (Champoux et al., 2004) The species M.luteus are obligate aerobes in that they rely completely on oxygen to survive and so can be found on one’s own microbiota, the surface of skin. (Madigan et al., 2009) Method A week before identification, 4 unidentified pure strains labelled (A-D) were each cultured on blood, bile aesculin and manitol salt agar that corresponded to each letter. The streak-plate technique was applied, a loop used to transfer the bacteria to the agar plates was sterilised under an open flame and left to cool, before each set of streaks. After a week, the agar plates were all examined and the type of results they produced was recorded. A single colony (seen by naked eye) was removed from the original (ordinary) agar plates. Each of these was inoculated over a few days and used for the Voges-Proskauer test. The reagents alpha napthol and 40% KOH were added, the tubes were then observed for colour changes. Also a catalase test was carried out, an inoculated loop was used to transfer a small amount from each strain (from the ordinary agar plates) to a microscope slide and hydrogen peroxide was added. Those that bubbled were noted as positive. All results from the various bioche mical tests were compiled in table format the catalase; Voges-Proskauer; haemolysis (blood agar); ability to produce aesculetin (bile agar) and ability to grow (on manitol salt agar). The 4 strains of bacteria were thus identified. Separately, an API test was simulated of an ‘unidentified’ staphylococci bacterium. Each well of the incubation box for the API was filled with distilled water followed by an ampoule of the bacteria which was inoculated and prepared to the correct McFarland standard tube of 0.5. Mineral oil filled the outlined wells. The box was incubated for a few days; reagents were added to the corresponding wells and after 10 minutes observed for colour changes. Reagents VP1 and VP2 were added to the VP well; NIT1 and NIT2 to NIT well and lastly Zym A and Zym B to PAL well. The test colour result for each well was then noted (either positive or negative) on an API Staph strip and matched with the identification table of the various Staphylococcus species. The staphylococcus species was thus identified. Results The 4 unidentified strains (labelled A-D) were exposed to various biochemical tests, the results from these are given below. Table 1: Results from the gram positive strains Results from the API test: A bacterium was then identified by the use of API test, a colour indication table was also provided to determine if the results were positive or negative. These results were jotted down on a test strip and compared with a test table to identify the species of Staphyloccocus. Figure 1: Test strip Figure 2: Identification Table of Staphylococcus species   (Provided by API Manufacturer) Discussion  Ã‚   Observation of the colour and characteristics of the pathogen, with the use of various biochemical tests can identify the bacterium causing the infection. (Madigan et al., 2009) This can be applied in this experiment. Referring to Table 1: The ability to produce haemolysis is dependent on bacteria to secrete a toxic substance called haemolysin, which is able to lyse red bloods cells. Thus blood agar is used which is a differential medium. (Willey et al., 2008) The type of haemolysis bacteria produce can be observed by the naked eye, as clearing zones around the colonies. A ÃŽ ²-haemolysis results in distinct, colourless clear zones of colonies, as the erythrocytes (of the blood agar) have completely lysed. The species S. pyogenes has the ability to secrete exotoxins, depending incubation conditions it will either secrete Streptolysin-O (anaerobic) or Streptolysin-S (aerobic). The pyogenic bacteria are distinguished from other streptococci by producing ÃŽ ²- haemolysis. (Willey et al., 2008) Whilst ÃŽ ±-haemolysis is the partial destruction of erythrocytes with some clearing and slight green discolouration, it is not as distinct as ÃŽ ²-haemolysis. The green tinge is a result of haemoglobulin being oxidised. Conversely M luteus and E. Faecalis produce Æ”-haemolysis i.e. no colour change or clearing zone on the agar as the bacteria are unable to produce haemolysin. (Greenwood et al., 2007) Furthermore the Lancefield method together with haemolysis testing can be used to identify pathogenic streptococci from other less evasive streptococci. (Greenwood et al., 2007) The Lancefield method involves the agglutination of antibodies with the cell wall antigens (C polysaccharide) each serotype is classified A-T, depending on the sort of antigen-polysaccharide nature of this reaction. (Willey et al., 2008). Voges-proskauer is used to indicate if the bacteria in question produce fermentation, this would depend on their culture needs – especially anaerobic bacteria which are unable to respire without the electron transport chain. (Willey et al., 2008) The red colour produced is a test positive for the production of acetoin or acetylmethylcarbinol in glucose fermentation. (Champoux et al.,2004) Referring to Table 1, S. aureus tests positive as it’s a facultative anaerobe. (Willey et al., 2008) Whilst M. luteus and Str. pyogenes can grow in aerobic conditions and so do not require the principles of fermentation, they test negative. Conversely, unlike anaerobes ability to produce fermentation, most aerobes possess the enzyme catalase. A positive catalase test results in bubble formation when hydrogen peroxide is added to a bacterium. The enzyme catalase is able to form water and oxygen from hydrogen peroxide. (Madigan et al., 2009)   The Streptoccocus pyogenes produce no gas, and instead utilise lactic acid to break down sugars. (Willey et al., 2008)   They catalase negative as the enzyme catalase is not present; so cannot break down hydrogen peroxide to form water and oxygen. (Greenwood et al., 2007) Staphylococcus tests positive and can utilise glucose to form acidic products. (Madigan et al., 2009) It’s also an aerotolerant anaerobe, it may lack the enzyme superoxide dismutase which can break down superoxide radicals, but can make use of manganese ions instead. This may have been an adaptative mechanism when the very first forms of bacteria were exposed to oxygen. (Madigan et al., 2009)   This en zyme is common in most pathogenic bacteria, and increases their virulence by neutralising the otherwise toxic hydrogen peroxide and minimizing death by phagocytosis by host cells. (Champoux et al., 2004)   M. luteus grow in aerobic conditions and can only utilise glucose in these conditions, this would explain why it would catalase positive, to neutralise toxic hydrogen peroxide.   (Madigan et al., 2009) Bile aesculin agar is selective and differential, black formation on the culture plate would indicate the ability of the bacterium to hydrolyse aesculin and mix with ferric citrate. (Mahon and Manuselis, 2000) The presence of bile salts will inhibit some types of bacteria like S. pyogenes and M.luteus (as seen on Table 1) Manitol is a selective media, only allowing some bacteria to tolerate it, like S. aureus   and E. faecalis. They are both able to utilise manitol by fermenting it to produce acid, thus lowering the pH the agar changes from red to a yellow colour as a result.   Incubation of S. aureus is slightly longer, and so a coagulase test can also be implemented. (Mahon and Manuselis, 2000)   Whilst haemolysis identifies pathogenic streptococci like Str. pyogenes, the manitol agar identifies pathogenic staphylococci. Also Str. pyogenes cannot grow on this agar, and so no visible colonies are formed. (Willey et al., 2008) While M. luteus has the ability to grow on manitol salt agar (visible colonies), so one would assume that it cannot utilise manitol, as there is no colour change present as it cannot produce acid. As mentioned, there are various API tests available; this experiment used an API Staph Test which identified Staphylococcus, micrococcus and kocuria genera. (CITATION)   The test kit was compared with the colour change table of the various substrates (when reagents are added) and the API test strip was marked accordingly for a positive or negative result. The test strip (Figure 1) was then compared to the identification table (Figure 2) and the unknown bacterium was identified as S. aureus. The limitations of this test is that a pure culture of bacteria must be used and that API’s are specific for a particular genera of bacteria, various API tests are available ( these include an API 20E to identify Enterobacteriaceae (Willey et al., 2008) Also any experimental error like not adding reagents correctly to specific well can also give false positives, thus not correctly identifying the species. Conclusion Identification of gram positive bacteria can be achieved by carrying out various biochemical tests.   Differential media like blood agar is useful in identifying the type of haemolysis and thus the pathogenicity of various bacteria (streptococci). Selective media like manitol salt agar inhibits growth of certain bacteria like streptococci, whilst also determining the presence of particular enzymes by the end products produced, this can be observed by colour changes. Various other biochemical tests are available and can produce rapid results – like the API. The simulation of identifying bacteria in this experiment, accentuated how vital these tests are in order to treat patients effectively. However it should be noted in realistic settings further biochemical tests and the use of modern technologies may be required to correctly identify microorganisms. References Greenwood, D.; Slack, R.; Peutherer, J., Barer, M. (2007) Medical Microbiology A Guide to Microbial Infections: Pathogenesis, Immunity, Laboratory Diagnosis and Control. 17th ed. Philadelphia: Elsevier Limited. Heritage, J., Evans, E.G.V., Killington, R.A. (1999). Introductory Microbiology. Cambridge: The Press Syndicate of The University of Cambridge Madigan, M., Martinko, J., Dunlap, P., Clark, D,. (2009). Brock Biology of Microorganisms. 12th ed. San Francisco: Pearson Benjamin Cummings Mahon, C.R., Manuselis, G. (2000) Textbook of Diagnostic Microbiology. 2nd ed. Philadelphia: Saunders An Imprint of Elsevier Mandal, B.K.; Wilkins, G.L.E.; Dunbar, E.M.; Mayon-White, R.T. (1996) Infectious Diseases. 5th ed. Oxford: Blackwell Science Ltd. Champoux, J.J.,   Drew, W.L., Neidhardt, F.C., Plorde, J.J.(2004) Sherris Medical Microbiology. 4th ed. USA: McGraw-Hill Companies, Inc. Willey, J.; Sherwood, L., Woolverton, C. (2008) Prescott, Harley, and Klein’s Microbiology. 7th ed. New York: McGraw-Hill.

Monday, February 24, 2020

Globalization Influence on General Electric Research Paper - 5

Globalization Influence on General Electric - Research Paper Example Ideally, GE relies on its engineers and research scientists for continued growth and given that these people are from different backgrounds, then this brings about cultural differences. Due to these cultural differences, then these experts need to be managed in a different manner. However, the management at GE feels that their well-established processes are capable of adopting all these people and make sure that they fit into the organization’s processes and hence ensure that it has continued success. However, this has not been the case and the company’s shares have been plummeting since the exit of Jack Welch, the company’s former CEO who was credited with introducing numerous management practices that insured success for the organization (Hill, 2010). Since the exit of Welch, the company has tried to come with a one fit all strategy to handle its staff. With the business environment becoming more complex in the United States, GE has been forced to turn to China where there is a guarantee of constant business for the conglomerate. However, this has not borne many fruits since the management did not try to come up with new management practices but rather adopted its traditional way of doing business in America. This was not actually what the management expected (Morrison, 2012). In order to deal with the arising changes in its Chinese firm, GE sacked all the expatriate managers since it felt like they were not performing. Naturally, when GE replaced the expatriate executives, the new ones that they exported also failed to deliver the expected results and it took so long for the company to get on its own feet. However, the Chinese firm has not been successful and in the next few years after inception, it experienced numerous unwarranted expenses that drove up the operating cost significantly.

Saturday, February 8, 2020

Social Groups Essay Example | Topics and Well Written Essays - 500 words

Social Groups - Essay Example In European countries it seems that more emphasis is placed on the enjoyment of life, and not necessarily an enjoyment of money. In America it is often believed that fun and enjoyment cannot be had without spending money, whereas in Europe citizens learn to enjoy the simpler aspects of life and pleasures that come free of cost. The main difference between the work ethics of Americans and Europeans is that the United States is a more capitalistic society. 1.) "Capitalism is a system of wage based labor and commodity production for sale, exchange, and profit rather than for immediate use of the producers" (Scott). In the United States, citizens feel that they have to work in order to enjoy life. They hold the philosophy that one must work in order to receive. Americans believe that everyone is out for themselves and that if one wants to improve their quality of life they must work for it. 2.) While the United States work ethic is definitely money oriented, it is not purely capitalistic. 4.) The United States government has adapted some practices with a socialist background and applied them to the American way of life. Examples of these practices can be seen in free education for all, free healthcare for those that qualify, free food and food stamps for those that are in need, etc. In Europe, many citizens enjoy a more relaxed work schedule with longer weekends and more vacati

Wednesday, January 29, 2020

Pennsylvania School Essay Example for Free

Pennsylvania School Essay It is my fervent wish to attend the prestigious University of Pennsylvania School of Dental Medicine primarily because of the instant respect that a graduate of this 128 year old institution commands and also because I share the university and I share the same mission objectives and beliefs. I firmly believe that my goal of becoming and exceptional citizen who strives to offer the best available, affordable and even free dental services to those in need will be lent a guiding hand by the university. This is because just like the university, I believe that dentistry is a lifelong commitment that requires a lifetime of learning and discipline that will help me achieve my objective of providing a necessary dental care to the people who need it the most regardless of their status in life and financial capability. Achieving this will be possible for me because Penn Dental Medicine encourages their students to undertake dental researches and education that most often thrusts their students into the center of innovative and improved dental care methods. It is my hope that I will be given the chance to join the roster of students of Penn Dental Medicine who have gone on to become leaders in their chosen areas of dental specialization by attending regular classes in the atmosphere of the school that is conducive to students like me who strive for constant learning. Since Penn Dental Medicine encourages free expression, reasoned discourse, and diversity of ideas, I believe that I can only blossom and reach my full intellectual potential while attending this university because I will be allowed to explore my full potential not only as dental student and future dentist, but also as an individual whose rights are respected by the university as well.

Tuesday, January 21, 2020

The Relationship Between War and Man Essay -- Psychology

War dates back to the earliest of ages. Leaders have come out triumphant and countries have come out ravaged. Entire generations have been extinguished and humanity’s morale destroyed; all at the cost of a victory. Everyone is familiar with war, however we are not so quick to understand the lasting toll it takes on those who experience it for themselves. War has been fought through out many countries for various reasons since the beginning of times, the tactics and warfare themselves may have changed, but the meaning of war remains the same. In turn the soldiers, whom give it all in the name of their countries, never come back the same. It is glittered with words like glory, honor and devotion, however war, in my eyes, is anything but. It brings about many more problems, one of which is the substantial psychological effects it has on those who experience war first hand. World War I was said to have been the war to end all wars. We now know that not to be true as there have been countless wars since that proposition. The attitudes surrounding the initiation of World War I were very distinct from that of proceeding wars to come. Citizens were excited, families were proud to know that their sons were enlisted and patriotism and brotherhood were alive and well. Young men were very much encouraged to join the war effort and advertisements soliciting the call to arms were seen in a positive light. Enlistment was something expected of these young men, they wouldn’t dare be the ones to be â€Å"ostracized† or called â€Å"coward† . With no way around the Great War many did indeed join the armed forces; little did they know what they were in for. â€Å"A word of command† , and a powerful one at that, put these young men on the path to destruction. ... ...rd we take, as a war to end all wars was virtually never in sight. We must become human again; as it seems to be the only way to make existence worthy once again. Works Cited Cohen, Harold, PH. D. "Two Stories of PTSD." PsychCentral. PsychCentral, May 2012. Web. 9 May 2012. . Remarque, Erich Maria. All Quiet on the Western Front. New York: Ballantine Books, 1982. Print. US National Library of Medicine. "Post-traumatic Stress Disorder." PubMed Health. National Center for Biotechnology Information, 2012. Web. 9 May 2012. . WebMD. "Post-traumatic Stress Disorder." WebMD. WebMD, 2012. Web. 9 May 2012. . Sassoon, Siegfried. â€Å"Dreamers.† 1968.

Monday, January 13, 2020

Outline and Evaluate Cross-Cultural Studies of Gender Role Essay

There have been various studies that have observed elements of gender roles in other countries, one such study was conducted by Williams and Best, the study explored gender stereotypes in 30 different nations involving 2800 university students as participants. They were given a 300 item adjective checklist and asked to decide whether an item was most associated with men or women. What they found out was that there was a broad consensus across countries with men being seen as more dominant and aggressive and women being seen as nurturing and defendant. This supports the common stereotype of both genders, that males are â€Å"dominant and aggressive† and that females are â€Å"nurturing and defendant†. The findings from this study do have strengths, due to the sample used. The studies sample firstly was large and also very diverse in terms of culture, religion and ethnicity (expected of universities) and because of this the population validity of the findings increases and makes the results more generalizable and representative of the wider population, this means the conclusion of gender roles being consistent throughout cultures is applicable to the general population. However there is a flaw within the study, you could say that although the sample was drawn from a large geographical pool, which should indicate representativeness, they were all students who share common attributes and viewpoints and so they may not being necessarily representative of the population of their country and all social groups within. Also the construction of the checklist did not include an equal category alongside the male and female category, so this means that the division between the male and female categories may be exaggerated, thus prompting the students to believe that there is a gap between men and women and thus making them draw upon their inner stereotypical views. Also there are methodological flaws, the checklist comes into account again as it is developed by Western psychologists, because of this the westernised perspective behaviours considered in one culture to be feminine may not be considered feminine in another, so therefore the findings may be of little use to those in other cultures. This study suggests that there are universal stereotypes about male-female characteristics therefore indicating that gender roles are influenced more y our biology and evolution rather than socially constructed. However its arguable that the findings lack validity and that empirical evidence of cross-cultural studies on gender roles is less useful than initially believed. Another study is one conducted by Margaret Mead, she studied social groups in Papua New Guinea. Initially, she argued that the â€Å"Arapesh† men and women were gentle, the â€Å"Mundugumor† men and women were violent and the â€Å"Tchambuli†exhibited gender role differences with women being more dominant and men dependable. She concluded that this date demonstrated cultural determinism and that gender differences are determined by social factors. However Mead later changed her view to one of culture relativism. When she re-analysed her data she realised that although both sexes of the Arapesh were non-aggressive and both sexes of the Mundugamor were aggressive, in all three societies the men were more aggressive than the women. This suggests that some behaviours are innate and universal, but the degree to which these behaviours are expressed is relative to the particular culture. The study was a natural experiment, so Mead was observing the groups in their usual enviroment, it could be argued that she was noting their true behaviour, however it could be argued that the natives were simply providing Mead with the information she wanted to hear and therefore the study may not be as valid as it seems. Also there are methodological issues with the research conducted by Mead, as she used ethnographic field research and the data would have been gathered through participant observation, interviews and questionnaires, all methods whereby the results are easily subject to observer bias. Mead would have had to speculate on what the data potentially meant and acknowledge that her own cultural biases will have affected the interpretation. Due to the fact results may not be objective and the fact that non-scientific methods were used to collect data (both key features of psychology as a science), the validity of the findings seems to decrease and due to this reduced validity we cannot accurately conclude that gender roles do vary depending on culture to the studies methodological flaws. However, there is further evidence to support the assumption that gender roles are not consistent worldwide, Antonia Young carried out a study on the unusual gender roles in Albania. She found a group called the Albania virgins who were born into families which lacked a male presence and thus adopted the male role, committed to being a virgin and dressed and acted as men. The society accepted them as male and they were admitted to all male clubs and social groups. This suggests that societies create gender roles based on the needs of their society/culture and therefore shows that genders do vary across cultures. In conclusion, cross cultural studies help us to establish whether nature or nurture has the greater influence over gender roles. Both Mead and Young’s studies imply that nurture and social influences have a greater influence on gender roles, however evidence from William and Best lies on the nature side of the debate by indicating that our biology is more dominant.

Sunday, January 5, 2020

Futalognkosaurus - Facts and Figures

Name: Futalognkosaurus (indigenous/Greek for giant chief lizard); pronounced FOO-tah-LONK-oh-SORE-us Habitat: Woodlands of South America Historical Period: Late Cretaceous (80 million years ago) Size and Weight: About 100 feet long and 50-75 tons Diet: Plants Distinguishing Characteristics: Quadrupedal posture; thick trunk; extremely long neck and tail About Futalognkosaurus Youd think it would be hard for a 100-foot-long dinosaur to keep a low profile, but the fact is that paleontologists are still digging up new genera. One of the latest examples is the oddly named Futalognkosaurus, 70 percent of whose skeleton has been reassembled from three fossilized specimens discovered in Patagonia (a region of South America). Technically, Futalognkosaurus is classified as a titanosaur (a type of lightly armored sauropod with a widespread distribution during the late Cretaceous period), and with 70 percent of its skeleton accounted for, some experts have hailed it as the most complete giant dinosaur known so far. (Other titanosaurs, such as Argentinosaurus, may have been even bigger, but are represented by less complete fossil remains.) Paleontologists have made significant process identifying the exact place of Futalognkosaurus on the titanosaur family tree. In 2008, researchers from South America proposed a new clade called Lognkosauria, which includes both Futalognkosaurus, the closely related Mendozasaurus, and the possibly even more gigantic Puertasaurus. Tantalizingly, the same fossil site where these titanosaurs were discovered has also yielded the scattered bones of Megaraptor, a meat-eating dinosaur (not a true raptor) that may have preyed on the juveniles of Futalognkosaurus, or scavenged the bones of adults after they perished.