Will North Korea abandon its nuclear weapons programme Evaluate the Essay - 1

Will North Korea abandon its nuclear weapons programme Evaluate the arguments for and against - Essay Example a, Russia, Japan, and South Korea, have all expressed their wish for a denuclearised Korean Peninsula, while the UN Security Council (UNSC) continues to impose sanctions aimed at deterring North Korea from advancing its nuclear programme. However, the North Korean leadership continues to view nuclear weapons as an essential instrument to ensure its survival, as well as to give it a bargaining platform with its neighbours (Cumings, 2003: p10). Therefore, while the idea of denuclearisation of the Korean Peninsula and inclusion of North Korea in such a strategy remains an interesting and desirable proposition, it is ultimately unrealistic as long as the current regime remains in power. Most advocates of a denuclearised North Korea, according to Yi (2009: p766), argue for this outcome on the basis that North Korea may be convinced to abandon its programme if Japan, South Korea, and the United States committed never to pursue a nuclear attack on North Korea through a treaty. This nuclear weapon-free zone concept in Northeast Asia generally refers to North Korea, South Korea, and Japan at its core, while Russia, China, and the US would pledge not to use nuclear weapons in this zone. A treaty would bind signatory parties to refrain from possessing, producing, and testing such weapons. Moreover, another possibility underlying this zone is that the other countries may sign the treaty with North Korea joining at a later date, similar to the Latin America nuclear weapons-free zone, which Argentina and Brazil joined ten years after ratification by other countries (Yi, 2009: p766). In such a scenario, therefore, it may be assumed that North Korea would be willing to abandon its nuclear weapons program should the leadership get assurances that nuclear weapons will never be used within the zone, including against them. Cha and Kang (2003: p61) argue that there are several conditions under which North Korea may denuclearise, noting that its leadership may cave to international

Science Investigatory Project Essay Example for Free

Science Investigatory Project Essay Dissatisfaction and discouragement are not caused by the absence of vision. Many things from afar are cannot be seen by the naked eye. Unlike cameras, eyes don’t have the capacity to magnify or zoom. In today’s generation, many people call for the use of binoculars but not everyone can afford. Due to this problem, the researchers decided to conduct this study â€Å"Improvised Binoculars out of worn-out gadgets.† To seek an alternative and affordable binoculars. Binoculars are a pair of identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, allowing the viewer to use both eyes when viewing distant objects. Most are sized to be held using both hands, although sizes may vary from opera glasses to large pedestal mounted military model unlike a telescope, binoculars give users a 3 dimensional image: for nearer objects the two views, presented to each of the viewer’s eyes from slightly different viewpoints, produce a merged view with an impression of depth. Modern binoculars consist of two barrel chambers with an objective lens, eyepiece and a prism inside. The prisms reflect and lengthen the light while the objective lenses enhance and magnify images due to stereoscopic vision. As telescopes were improved, binoculars evolved. Binoculars consist of an objective lens and eyepiece with two facing, right angle prisms arranged to invert and correct two facing, right angle prisms arranged to invert and correct the orientation of the image. The applications of binoculars are vast, ranging from being used in military operations to leisure activities. A must for bird-watchers and hunters, bi noculars are even used at sporting events by spectators who may be seated far from the action, thus using binoculars to get clearer and closer views of the action. Many tourist destinations around the world also have swivel-mounted binoculars to allow tourists to get better views of distant objects. In professional situations, militaries use binoculars for day-to-day operations. Binoculars are essential for them as with the binoculars, the military personnel would be able to spot enemies at a distant and take the necessary action. Not only that, they can also safeguard their territory and prevent and intruders from coming in. Their use, together with sophisticated 21st century technology makes the military much more efficient than it previously was. Statement of the Problem The main purpose of the study is top produce a simple improvised binocular. The researchers aim to answer the following questions: a. What are the methods to be used in constructing simple prism binoculars? b. Are binoculars a good magnifier? c. Compare the improvised prism binocular with commercial binoculars. Hypotheses * Null Hypotheses (Ho) There is no significant difference between the images magnified on the improvised prism binoculars and that on the commercial binoculars. * Alternative Hypotheses (Ha) There is a significant difference between the images magnified on the improvised prism binoculars and that on the commercial binoculars. Significance of the Study Binoculars are a handheld optical instrument composed of two telescopes and a focusing device, and usually having a prism to increase magnifying ability. Binoculars are used to view distant objects using both eyes. The applications of binoculars are vast, ranging from being used in military operations to leisure activities. A must for bird-watchers and hunters, binoculars are even used at sporting events by spectators who may be seated far from the action, thus using binoculars to get clearer and closer views of the action. Many tourist destinations around the world also have swivel-mounted binoculars to allow tourists to get better views of distant objects. An example can be the Grand Canyon, where tourists would not be able to see far away objects, thus these binoculars have been installed for the convenience of the tourists. In professional situations, militaries use binoculars for day-to-day operations. Binoculars are essential for them as with the binoculars, the military person nel would be able to spot enemies at a distant and take the necessary action. Not only that, they can also safeguard their territory and prevent and intruders from coming in. This will give the researchers an idea of making improvised prism binoculars. Some consider cans, lenses from worn-out gadgets and caps of plastic bottles as waste and there is nothing to do with them. But these materials can be a good raw material that has the potential in making improvised binoculars, which will help to see distant objects, instead of buying those expensive binoculars. This is the reason why the researchers will make an improvised prism binocular. Scope and Delimitation This study will only focus on making improvised prism binoculars from gadgets that are no longer in use or worn out. This study will show the steps and the procedures to make simple prism binoculars and show the comparison between the said binoculars and the commercial ones. II. A. Review of Related Literature History of binoculars Almost from the invention of the telescope in 17th century the advantages of mounting two of them side by side for binocular vision seems to have been explored. Most early binoculars used Galilean optics; that is, they used a convex objective and a concave eyepiece lens. The Galilean design has the advantage of presenting an erect image but has a narrow field of view and is not capable of very high magnification. This type of construction is still used in very cheap models in and in opera glasses or theater glasses. The Galilean design is also used in low magnification binocular surgical and jewelers loupes because they can be very short and produce an upright image without extra or unordinary erecting optics, reducing expense and overall weight. They also have large exit pupils making centering less critical and the narrow field of view works well in those applications these are typically mounted on an eye-to-eye glass frame or custom-fit onto eye glasses. An improved image and high er magnification can be achieved in binoculars employing keplerian optics, where the image formed by the objective lens is viewed through a positive eyepiece lens (ocular). This configuration has the disadvantage that the image is inverted. Porro prism binoculars are named after Italian optician Ignazio Porro who patented this image erecting system in 1854 and later refined by makers like the Carl Zeiss Company in the 1890’s. Binoculars of this type use a porro prism in a double prism Z-shaped configuration to erect the image. This feature results in binoculars that are wide, with objective lenses that are well separated but offset from the eyepieces. Porro prism designs have the added benefit of folding the optical path so that the physical length of the binoculars is less than the focal length of the objective and wider spacing of the objectives give a better sensation of depth. Thus, the size of the binoculars is reduced. Binoculars using roof prisms may have appeared as early as the 1870’s in a design by Achille Victor Emile daubresse. Most roof prism binoculars use either the Abbe-Koenig prism (named after Ernst Karl Abbe and Albert Koenig and patented by Carl Zeiss in 1905) or Schmidt-Pechan prism (invented in 1899) designs to erect the image and fold the optical path. They have objective lenses that are approximately in line with the eyepieces. Binoculars tend to come in two main styles, the Roof Prism and the Porro Prism design, both have their unique advantages and disadvantages over each other and so often it will be down to your specific needs and preferences as to which you should choose. Roof Prism Binoculars one of the two main styles of binoculars is the Roof Prism (the other being Porro Prism), this refers to the type of prism used in their construction. In this design the prisms are aligned with each other in a straight line, and thus they tend to be sleeker and more compact binoculars than the Porro prism design. You can easily identify a roof prism binocular as the eyepieces and the large objective lenses line up with each other. Roof Prism Binoculars Advantages: * Compact Design * Less internal parts than porro prism design, so less to go wrong and easier to make dust and waterproof. Disadvantages: * The image quality of roof-prism binoculars can suffer slightly because of the aligned prisms, although the top models of the roof-prism and porro-prism binoculars are now generally considered to have equal optical quality. To be really good, roof prism binoculars have to be in the high price range. Do not attempt to economize on roof prism binoculars. * Good for Ideal general use binoculars that can be used for bird-watching, wildlife viewing and at sporting events. Porro Prism Binoculars It is easy to identify a Porro Prism binocular because the eyepieces and the objective lenses are offset from each other (objective lens is not in line with the ocular lens), this is because of the design of the prism (porro) used in its construction. Advantages: †¢ Porro prisms have objective lenses spaced wider than roof prisms, and so can produce a slightly better stereoscopic image than the roof prism design. †¢ Cheaper to make quality porro prisms than roof prisms so they tend to be cheaper to buy. Disadvantages: †¢ Less compact design than roof prism binoculars †¢ More moving parts, more to go wrong and harder to make fully water and dust proof. Good For Like the roof prisms, porro prism binoculars make perfect general use optics ideal for things like bird-watching, wildlife viewing and at sporting events. Review of Related Studies Creating Binoculars The prismatic telescope is an astronomical telescope plus a pair of prisms for erecting the image. The most common example of this type of construction is the binocular instrument. One half of a binocular is a monocular. Some telescopes are used for a specific purpose and are named accordingly. A typical example is a spotting scope, which is used to view the target in rifle shooting. Prisms: Prisms are polished, angular pieces of glass, the kind commonly used in telescopes being 45-45-90-deg. prisms. The long side is the face, while the two short sides are the reflecting surfaces. The size of the prism is the width of the face Made specifically for telescopes, the prisms are grooved across the face in order to make a definite dividing line and avoid ghost images which would be caused by overlapping rays at this point. The ends are usually rounded to conserve space. The prime advantage of the prism erecting system is compactness. It adds somewhat to the bulk of the instrument but shor tens the length considerably. The prism glass has an elusive quality of brilliance but actually the light loss through the two prisms is somewhat greater than through the two erecting lenses of a lens erecting system. The 23X prismatic spotting scope This design calls for a 20-in. focal length objective, which, with a 22-mm. focal length eyepiece (from Army 6X), gives 23-diameter magnification. Prisms are 1-in. face. The scope body is of wood construction in simple box form. The first prism, the one the light strikes first, is located in an upright position at the back of the box; the second prism is mounted flat on the box bottom. Plywood spacers hold the prisms in place and also provide for the passage of the cone of light admitted by the objective. The eyepiece is fitted in a threaded mount. This type of focusing is satisfactory at set distances but is much too slow for general use. If you want this scope for general observation, it should be fitted with spiral focusing like the 10X monocular to be described later. It would also be practical to focus with a simple draw tube system. The principal point of the construction is to get the various holes lined up square. Use prism center lines as a guide and locate all holes from one master pattern drawn on cardboard Base on which the floor flange is mounted pivots on a carriage bolt and is tilted by means of a tilting screw. Designing- prismatic telescopes Designing your own prismatic telescopes follows much the same procedure as used for astronomical and terrestrials. Primary consideration should be given the objective and eyepiece. The prisms contribute nothing to the magnification; therefore, the power you want must be obtained entirely by the ratio of FO to FE. Prisms should be of such a size or so located as to receive the full cone of light from the objective, although it is practical to sacrifice extreme edge rays. The layout (at top of drawing) is what you make to determine the size and location of prisms and also the general overall dimensions. In this example, the objective has a 52-mm. diameter by 193-mm. focal length (from Navy 7X binocular) and the prisms are 1-in. face (from Navy 7X). As used by the Navy, this glass has a 27-mm. eyepiece, which gives a magnification of 7 diameters. If you want higher magnification, you have to use a shorter focus eyepiece. The Army 6X binocular eyepiece, 22 mm, could be used and would giv e you 9X. The eyepiece shown uses an Army binocular eye lens, but a shorter focus field lens, the combination giving 20-mm. focus, hence, about 10X magnification. The preliminary calculation should determine the exit pupil and luminosity. This glass has excellent illumination at 92 percent. However, Don’t get the idea that the 13 percent rating of the 23X spotting scope is hopeless—13 percent is a good value for anything over 20X magnification. It is worth mentioning here that prism instruments are often rated for illumination on the basis of the exit pupil squared. Thus, if the scope has a 5-mm. exit pupil, it would be rated 25. Using this calculation, the 100 percent standard would be the normal size of the eye pupil, squared: 25 for daylight and 49 for night. Bench setup Set up the objective and focus on well-lighted copy or a bare light bulb, not less than 20 ft. from lens. Use tracing or waxed paper as a ground glass to pick up the image as in Fig. 49. Measure the distance from the rear side of the objective to the image plane. Start your layout and transfer this dimension to the layout. Next, put the two prisms face to face and move the assembly back and forth until you pick up a sharp image of the copy or light bulb. Measure the distance to the face of the first prism and set off this distance on your layout, now you will note that the distance the light travels through a 1-in. prism is 2 in., a total oX 4 in. for both prisms. Set off this distance, C, on your layout to establish the back image plane. Determine the image size. In this instance, the multiplying factor is .070, and this figure multiplied by the focal length of the lens (7% in.) gives .53 in. for the image size. Call this Ha in. for an even figure and mark the image size at the normal image plane and again at the back image plane, as indicated by L. Draw lines K and M representing the marginal rays and the full cone of light. Your prisms must catch the marginal rays K and also as much of the weaker edge rays as possible. The best way to determine prism-placement is to make -two 1 by 2-in. oblongs of cardboard or celluloid. Manipulate these over your layout. The forward edge of the first oblong represents the face of the first prism. You can tell at a glance how far forward you can push it and still pick up the marginal rays. The distance between the two oblongs is the spacing between the prisms. The distance between the back edge of the second oblong and the back image plane must be sufficient to permit focusing. What you finally arrive at in this case is D, %s-in. allowance for the distance the image plane will set inside the eyepiece tube; E, % in. for focusing travel; F, %-in. prism spaci ng; G, 2 in., the distance through the second prism; H, %-in. prism spacing again, coming back; I, 2 in. for the first prism, arriving at J,-the face of the first prism. This may sound complicated, but it is really very simple if you are actually on the job. If desired, you can now draw an outline of the prisms. This shows both prisms flat; the same way you test them in the bench setup. At this point J, it will be noted that the face of the prism catches all of the marginal rays and about halfway out to the lines representing the full cone of light. As mentioned before, it is practical to sacrifice some or all of the weak edge rays, so that this placement of the first prism face is quite satisfactory. What next? Well, you know that the maximum cone of light you can catch on the first prism is 1 in. in diameter at J, so lines drawn from here to image size at the back image plane will establish guide lines for hole diameters needed to pass this same cone of light back to the image pla ne. These lines are marked N in the drawing, and O, for example, shows the diameter of the hole at the back face of the second prism. If you want to use one or more glare stops ahead of the prisms, the hole diameters are determined in the same way, as at P. Monocular construction You will need two wood blocks exactly 1 in. thick to house the prisms. The Vs-ia spacing between prisms is taken up by a spacer of %-in. plywood, and similar plywood pieces are used at the back and front of the housing. The whole thing is glued up like a triple Decker sandwich, the prisms being held securely in the cutouts and between the various layers. Work carefully to prism center lines. Be sure that prisms are exactly at right angles since any rotation here will rotate your image twice as much. Prisms must be spotlessly clean and polished. The eyepiece tube is 1 in. in diameter, this size permitting it to work alongside No. 1 prism; Focusing is by means of a spiral groove cut half way across the eyepiece. Shows the monocular partly assembled and also shows how the turning which joins the main tube to the prism housing is cut away to fit over the second prism covered with a gray pebble-grain oilcloth. General notes Cut the main tube long when making any prism telescope. Check the final position of the objective by actually using the instrument; run the eyepiece in as far as it will go and then place the objective so that distant objects are in focus. Then the full focusing range is available e for picking up nearer objects. The 23X spotting scope £ will focus down to about 40 ft.; the 10X monocular to about 30 ft. or even 20 if you want to make it that way. If you use spiral focusing, it is necessary to know in advance how much you will need for focusing. This travel will be very short with a short focus lens, but much longer with a long focus objective. Allow % in. for lenses less than 10-in. focus; % in., up to 14-in. focus; 1% in. at 18 and 1% in. at 20. These allowances will let you focus down to 30 or 40 ft. in all cases, -possibly closer. When you make a bench setup at close range , remember that this represents the maximum extension of your telescope. If you make a bench setup by focusing on a distant object (this is advisable if you are using an objective of over 20-in. focal length) the setup will represent the telescope at its shortest draw. The Kellne r type of eyepiece gives best results with all prismatic instruments. The objective should always be a cemented achromat. If the lens is not cemented l^^^^^^^ M when you get it, you can dummy test it by cementing with glycerin. Final cementing should be done with Canadian balsam; i n a pinch you can use a good grade of water white (clear) lacquer. The diameter of the objective controls the luminosity of the telescope. The diameter of the objective does not control the field of view; except in the Galilean instrument, you can see just as much through, a small objective as a large one.

Study of Genotype X Environment Intraction in Asiatic Cotton Gossypium

Cotton is known as â€Å"White Gold†. Gossypium arboreum belongs to family Malvaecae with diploid set of genome have 13 chromosome number. Genotype Ãâ€" environment (GE) interactions have major role in development of improved cultivars. A cultivar is said to be commercially successful, if it performs well across the range of environments in which it grows. The differential response of a genotype or cultivar for a given trait across environments is defined as the genotype Ãâ€" environment interaction (G Ãâ€" E). Bilbro and Ray (1976) indicated that a successful breeding program should focus efforts on genotype yield level (average yield compared to standards), adaptation (what environment does the genotype best perform in), and stability (how consistent does the genotype yield compared to others). Genotype refers to the set of genes possessed by individual that is important for the expression of traits under investigation. The environment is defined as all non-genetic factor s that influence the expression of the trait and influence the growth and development of individuals. G Ãâ€" E interaction is a differential genotypic expression across environments (Basford and Cooper, 1998). According to Romagosa and Fox (1993), G x E interaction reduces association between phenotypic and genotypic values of a genotype. This may cause promising selections from one environment to perform poorly in one and better in another environment, forcing plant breeders to examine genotypic adaptation (Sharma et al., 1987). Varieties are tested in many environments due to changing their performance and adaptation ability. However, important G Ãâ€" E interactions decreases relationship between phenotype and genotype and also genetics improvements in breeding programmes (Comst... ... (1963) Genotype x environment interactions statistical genetics and plant breeding. Eds. Hanson, W. D. and Robinson H. F. National Academy of Science, National Research Council Publication, 982 : 164-196. Eberhart, S A and Russell R A (1966) Stability parameters for comparing varieties. Crop Science, 6 : 36-40. Lukonge E P (2005) Characterisation and diallel analysis of commercially planted cotton (Gossypium hirsutum l.) germplasm in Tanzania. Phd Thesis, University of the Free State, Bloemfontein, South Africa Myers G O (2004) Estimation of potential breeding value and genotype stability of cotton strains and varieties. http://www.cottoninc.com. Romagosa I and Fox, P N (1993) Genotype x environmental interaction and adaptation. In: M.D Hayward, N.O. Bosemark and I. Romagosa (Eds.), Plant breeding: Principles and Prospects pp 373-390. Chapman and Hall, London.

Contemporary issues on mobility and work spaces

Oxford Encyclopedia of Economic History. Retrieved 24 February 2011 . – also Jump up A A Legal Bridge Spanning 100 Years: From the Gold Mines of El Dorado to the ‘Golden' Startups of Silicon Valley By Gregory Grooms, 2010. Assignment 1, mobility – Threaten Darkish First let me explain how this essays goes which I tough it would look and sound better if the definition and samples come first and then after that and also in between I refer them to interior design and our roles and use as one.I'll start with the definition of the word mobility to get to know this term and see it's difference from the other use of mobility as in the new technology and mobile APS for workplaces. Therefore â€Å"Mobility' indicates a worker's ability to physically move around freely in he workplace to accomplish work. Mobility for work can be assisted with items such as a wheel chair, crutches, canes, a desk near the door, a scooter to ride between distant buildings, and a shuttle bus.M obility also refers to a worker's ability to take advantage of various Job opportunities ( I will write more on this issue below), including the ability to relocate, move to a superior Job position, commute a particular distance to work daily, or change positions due to family and civic responsibilities. Some impediments to the mobility of labor include personal hindrances such as geographical location and ability to move, physical and mental ability, and prior Job experiences. Social/legal hindrances to mobility include a lack of educational opportunities, family responsibilities, and various laws.A frequent use of the word, mobility, occurs when organizations use the term to define the upward mobility of employees. An employee with upward mobility has the appropriate mix of needed qualities and characteristics including experience, knowledge, skills, education, cultural fit, and availability. An employee with upward mobility potential is ready for promotional opportunities*. Now a t this point I going to write further more about the mobility of employees and various Job opportunities to see what that points to exactly and how that is related to mobility.Employee mobility is an issue that has taken on a whole new meaning as more and more businesses have gone global. Employees today are commonly asked to take assignments in company locations outside their home country. These kinds of opportunities are seen as Contemporary Issues in Interior Architecture- Fall 2014 2 benefits by many employees who enjoy experiencing new cultures and the multi- cultural exposure. Managing employee mobility is important though, because without the right training and planning, employees moving to foreign countries will not be prepared to meet the challenges such moves present.Your company does not want to find itself faced with loss of productivity, or worse, loss of its best managers because of lack of planning. Being prepared to address the issues related to employee mobility sho uld be included in the company's strategic planning. Quality of living in this matter can be an issue if a company frequently transfer employees within the country or outside the country. Either way there are concerns which should be addressed in these compensation and benefits packages.For example, in the US, a manager transferred from a small town in Texas to a large northeastern city will be faced with many of the same issues as an employee transferred from the US to Canada and that is a very simple and the most easiest transfer in contrast with moving to India or china, a completely different culture. These concerns or issues include cultural and compensation differences. These differences become more pronounced when the company re-assigns employees from a developed country to a third world country.But it is really a matter of degree. Making sure that the staff are well prepared for these types of moves will insure the transition is smooth and they remain productive. After all t he reason managers are transferred is in order to better utilize their talents and skills within the company**. Here I can say our role as an interior designers may help with these issues but with prior researching, planning, somehow rearranging their working spaces even from their own country to their destinations.So that they can familiarize themselves and got to know those areas better prior going there to make them arm proof and repaper Just in case. Many transfers involve more than the staff also. The managers and workers in general have families who are as much a part of the move as the company employees. It's important for the company to recognize the needs of the employee's family also. Unless the staff feel as if their family will also benefit from the transfer without Jeopardizing their safety or welfare, company transfers will meet a lot of resistance.In these cases also our role as interior designers can come to great use by even designing and making their homes look lik e the one in future after move, better said aka and redesign them as person by hurt so they would not feel alienated. Now here are some instances of companies and how they help these employees related with this mobility matter. For instance the Whichever Workforce Mobility*** helps clients optimize their mobile workforce by delivering innovative solutions that make it faster, easier and more cost effective to deploy key talent and transfer critical skills anywhere in the world.Our expertise in Contemporary Issues in Interior Architecture- Fall 2014 3 relocation and assignment management ensures that our clients' mobility programs advance their business and workforce strategies. They deliver sustained customer value through unique service and engagement initiatives, including: – Trusted Partner – Next Practices – Fans – Balanced Scorecard Here again we as designers can be creative about those mentioned above. Even by being faster, easier and more cost effe ctive.By faster that can be as helping deploy critical talent at the speed of business by motivating them through Just by one look but by a great look. Because opportunity won't wait. By easier that can be as to Just open communication, transparency, mutual trust and boundless innovation. And by ore-cost effective that can be vast global resources and in-house expertise to control our clients' program costs which we can be ahead of it by being innovative or creative in these fields to somehow more economic but more fashionable.Also there is other term as labor mobility, which Labor mobility or worker mobility is the geographical and occupational movement of workers. Worker mobility is best gauged by the lack of impediments to such mobility. Impediments to mobility are easily divided into two distinct classes with one being personal and the other being systemic. Personal impediments include physical location, and physical and mental ability. The systemic impediments include education al opportunities as well as various laws and political contrivances and even barriers and hurdles arising from historical happenstance.Increasing and maintaining a high level of labor mobility allows a more efficient allocation of resources. Labor mobility has proven to be a forceful driver of innovations. There I also another International Labor Mobility. Which International labor mobility is the movement of workers between countries. It is an example of an international factor movement. The movement of laborers is based on a difference in resources between countries. According to economists, Over time the migration of labor should have an equalizing effect on wages, with workers in the same industries garnering the same wage.

A Freshwater Aquatic and Terrestrial Food Web

————————————————- Food web From Wikipedia, the free encyclopedia A  freshwater  aquatic  and  terrestrial  food web. A  food web  (or  food cycle) depicts feeding connections (what eats what) in an  ecological communityand hence is also referred to as a  consumer-resource system. Ecologists can broadly lump all life forms into one of two categories called  trophic levels: 1) the  autotrophs, and 2) the  heterotrophs. To  maintaintheir bodies, grow, develop, and to  reproduce, autotrophs produce  organic  matter from  inorganicsubstances, including both  minerals  and  gases  such as  carbon dioxide.These  chemical reactionsrequire  energy, which mainly comes from the  sun  and largely by  photosynthesis, although a very small amount comes from  hydrothermal vents  and  hot springs. A gradient exists between troph ic levels running from complete autotrophs that obtain their sole source of carbon from the atmosphere, to  mixotrophs(such as  carnivorous plants) that are autotrophic organisms that partially obtain organic matter from sources other than the atmosphere, and complete  heterotrophs  that must feed to obtain organic matter.The linkages in a food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs. The food web is a simplified illustration of the various methods of feeding that links an ecosystem into a unified system of exchange. There are different kinds of feeding relations that can be roughly divided into  herbivory,  carnivory,  scavenging  andparasitism. Some of the organic matter eaten by heterotrophs, such as  sugars, provides energy.Autotrophs and heterotrophs come in all sizes, from  microscopic  to many  tonnes  Ã¢â‚¬â€œ from  cyanobacteria  togiant redwoods, and from  viruses  and  bdellovibrio  to  blue whales. Charles Elton  pioneered the concept of food cycles, food chains, and food size in his classical 1927 book â€Å"Animal Ecology†; Elton's ‘food cycle' was replaced by ‘food web' in a subsequent ecological text. Elton organized species into  functional groups, which was the basis for  Raymond Lindeman's classic and landmark paper in 1942 on trophic dynamics.Lindeman emphasized the important role of  decomposer  organisms in a  trophic system of classification. The notion of a food web has a historical foothold in the writings of  Charles Darwin  and his terminology, including an â€Å"entangled bank†, â€Å"web of life†, â€Å"web of complex relations†, and in reference to the decomposition actions of earthworms he talked about â€Å"the continued movement of the particles of earth†. Even earlier, in 1768  John Bruckner  described nature as â€Å"one contin ued web of life†. ————————————————-Food webs are limited representations of real ecosystems as they necessarily aggregate many species into  trophic species, which are functional groups of species that have the same predators and prey in a food web. Ecologists use these simplifications in  quantitative  (or mathematical)  models  of trophic orconsumer-resource systems  dynamics. Using these models they can measure and test for generalized patterns in the structure of real food web networks. Ecologists have identified non-random properties in the  topographic  structure of food webs. Published examples that are used in  meta analysis  are of variable quality with omissions.However, the number of empirical studies on community webs is on the rise and the mathematical treatment of food webs usingnetwork theory  had identified patterns that are comm on to all. Scaling laws, for example, predict a relationship between the topology of food web predator-prey linkages and levels of  species richness. Trophic levels Main article:  Trophic level A trophic pyramid (a) and a simplified community food web (b) illustrating ecological relations among creatures that are typical of a northern  Boreal  terrestrial ecosystem. The trophic pyramid roughly represents the biomass (usually measured as total dry-weight) at each level.Plants generally have the greatest biomass. Names of trophic categories are shown to the right of the pyramid. Some ecosystems, such as many wetlands, do not organize as a strict pyramid, because aquatic plants are not as productive as long-lived terrestrial plants such as trees. Ecological trophic pyramids are typically one of three kinds: 1) pyramid of numbers, 2) pyramid of biomass, or 3) pyramid of energy. [4] Food webs have trophic levels and positions. Basal species, such as plants, form the first level a nd are the resource limited species that feed on no other living creature in the web.Basal species can be autotrophs ordetritivores, including â€Å"decomposing organic material and its associated microorganisms which we defined as detritus, micro-inorganic material and associated microorganisms (MIP), and vascular plant material. â€Å"[11]:94  Most autotrophs capture the sun's energy in  chlorophyll, but some autotrophs (the  chemolithotrophs) obtain energy by the chemical oxidation of inorganic compounds and can grow in dark environments, such as the sulfur bacterium  Thiobacillus, which lives in hot  sulfur springs.The top level has top (or apex) predators which no other species kills directly for its food resource needs. The intermediate levels are filled with omnivores that feed on more than one trophic level and cause energy to flow through a number of food pathways starting from a basal species. [12] ——————— Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€Ã¢â‚¬â€- In the simplest scheme, the first trophic level (level 1) is plants, then herbivores (level 2), and then carnivores (level 3). The trophic level is equal to one more than the chain length, which is the number of links connecting to the base.The base of the food chain (primary producers or  detritivores) is set at zero. [3][13]  Ecologists identify feeding relations and organize species into trophic species through extensive gut content analysis of different species. The technique has been improved through the use of stable isotopes to better trace energy flow through the web. [14]  It was once thought that omnivory was rare, but recent evidence suggests otherwise. This realization has made trophic classifications more complex. [15] Energy flow and biomass Main article:  Energy flow (ecology) See also:  Ecological efficiencyThe Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that ma ss is neither created nor destroyed in chemical reactions. In other words, the mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. [24]:11 Left:  Energy flow diagram of a frog. The frog represents a node in an extended food web. The energy ingested is utilized for metabolic processes and transformed into biomass. The energy flow continues on its path if the frog is ingested by predators, parasites, or as a decaying  carcass  in soil.This energy flow diagram illustrates how energy is lost as it fuels the metabolic process that transform the energy and nutrients into biomass. Right:  An expanded three link energy food chain (1. plants, 2. herbivores, 3. carnivores) illustrating the relationship between food flow diagrams and energy transformity. The transformity of energy becomes degraded, dispersed, and diminished from higher quality to lesser quantity as the energy within a food chain flows from one trophic s pecies into another. Abbreviations: I=input, A=assimilation, R=respiration, NU=not utilized, P=production, B=biomass. 25] Food webs depict energy flow via trophic linkages. Energy flow is directional, which contrasts against the cyclic flows of material through the food web systems. [26]  Energy flow â€Å"typically includes production, consumption, assimilation, non-assimilation losses (feces), and respiration (maintenance costs). â€Å"[5]:5  In a very general sense, energy flow (E) can be defined as the sum ofmetabolic  production (P) and respiration (R), such that E=P+R. The mass (or biomass) of something is equal to its energy content. Mass and energy are closely intertwined.However, concentration and quality of nutrients and energy is variable. Many plant fibers, for example, are indigestible to many herbivores leaving grazer community food webs more nutrient limited than detrital food webs where bacteria are able to access and release the nutrient and energy stores. [ 27][28]†Organisms usually extract energy in the form of carbohydrates, lipids, and proteins. These polymers have a dual role as supplies of energy as well as building blocks; the part that functions as energy supply results in the production of nutrients (and carbon dioxide, water, and heat).Excretion of nutrients is, therefore, basic to metabolism. â€Å"[28]:1230-1231  The units in energy flow webs are typically a measure mass or energy per m2  per unit time. Different consumers are going to have different metabolic assimilation efficiencies in their diets. Each trophic level transforms energy into biomass. Energy flow diagrams illustrate the rates and efficiency of transfer from one trophic level into another and up through the hierarchy. [29][30] ————————————————-It is the case that the  biomass  of each  trophic level  decreases from the base of the chain to the top. This is because energy is lost to the environment with each transfer as  entropy  increases. About eighty to ninety percent of the energy is expended for the organism’s life processes or is lost as heat or waste. Only about ten to twenty percent of the organism’s energy is generally passed to the next organism. [31]  The amount can be less than one percent in animals consuming less digestible plants, and it can be as high as forty percent in  zooplankton  consuming  phytoplankton. 32]  Graphic representations of the biomass or productivity at each tropic level are called  ecological pyramids  or trophic pyramids. The transfer of energy from primary producers to top consumers can also be characterized by energy flow diagrams. [33] Food Web A  food web  is a graphical description of feeding relationships among species in an  ecological community, that is, of who eats whom (Fig. 1). It is also a means of showing how  energy   and materials (e. g. ,  carbon) flow through a community of  species  as a result of these feeding relationships.Typically, species are connected by lines or arrows called â€Å"links†, and the species are sometimes referred to as â€Å"nodes† in food web diagrams. Relationships between soil food web, plants, organic matter, and birds and mammals. â€Å"The  herbivores  are usually preyed upon by carnivores, which get the  energy  of the  sunlight  at third-hand, and these again may be preyed upon by other carnivores, and so on, until we reach an animal which has no enemies, and which forms, as it were, a terminus on this food cycle. There are, in fact, chains of animals linked together by food, and all dependent in the long run upon plants.We refer to these as ‘food-chains', and to all the food chains in a community as the ‘food-cycle. ‘† A food web differs from a food chain in that the latter shows only a portion of the food web involving a simple, linear series of species (e. g. ,  predator,  herbivore,  plant) connected by feeding links. A food web aims to depict a more complete picture of the feeding relationships, and can be considered a bundle of many interconnected food chains occurring within the community. All species occupying the same position within a food chain comprise a trophic level within the food web.For instance, all of the plants in the foodweb comprise the first or â€Å"primary producer† tropic level, all  herbivores  comprise the second or â€Å"primary consumer† trophic level, and carnivores that eat  herbivores  comprise the third or â€Å"secondary consumer† trophic level. Additional levels, in which carnivores eat other carnivores, comprise a tertiary trophic level. Elton emphasized early on that food chains tend to show characteristic patterns of increasing body size as one moves up the food chain, for example from  phytoplankton  to inv ertebrate grazers to fishes, or from insects to rodents to larger carnivores like foxes.Because individuals of small-bodied species require less  energy  and food than individuals of larger-bodied species, a given amount ofenergy  can support a greater number of individuals of the smaller-bodied species. Hence, ecological communities typically show what Elton called a pyramid of numbers (later dubbed the Eltonian pyramid), in which the species at lower trophic levels in the food web tend to be more numerous than those at higher trophic levels.A second reason for the pyramid of numbers is low ecological efficiency: some  energy  is lost at each transfer between consumer and prey, such that theenergy  that reaches top predators is a very small fraction of that available in the plants at the base of the food web. Although there is wide variation among types of  organisms  and types of  ecosystems, a general rule of thumb is that available  energydecreases by about a n order of magnitude at each step in the food chain.That is, only about 10% of theenergy  harvested by plants is consumed and converted into herbivore  biomass, only 10% of that makes it into  biomass  of primary carnivores, and so on. Thus, the structure of food webs is dictated in part by basic constraints set by  thermodynamics. The predictable dissipation of  energy  at each step in food chains is one of the factors thought to limit the length of most food chains to a maximum of four or five steps. Cohen et al. (2003) emphasized that the correlations mong body size, abundance, and trophic level produce a characteristic trivariate structure to (pelagic) food webs (Fig. 2). The pyramid of numbers is less obvious at the most basal levels in terrestrial communities based on trees, which are typically much larger than theherbivores  that feed on them. Pyramids of numbers or  biomass  may even be inverted in cases where the microscopic plants that support the web s how very rapid turnover, that is, where they grow and are eaten so rapidly that there is less plant  biomass  than herbivore  biomass  present at a given time. ————————————————-Decomposers are an assemblage of small  organisms, including invertebrates,  fungi, and  bacteria, that do not fit neatly into any trophic level because they consume dead  biomass  of organisms from all trophic levels. Decomposers are a critical component of the food web, however, because they recycle nutrients that otherwise would become sequestered in accumulating detritus. All food chains in a community constitute a food web. A  food web is simply the total set of feeding relationship amongst and between the species composing a biotic community. These relationships may achieve considerable complexity.With many food chains and cross connecting links, there is greater opportunit y for the prey and predator population in an ecosystem to adjust to the changes. ————————————————- The producer-consumer arrangement is one kind of structure known as trophic structure(trophic = food) and each food (nutritional) level in the food chain is called trophic level  or energy level. The first trophic level in an ecosystem is occupied by the plants-producers (green plant-primary producers), because they utilize solar energy which is transformed to chemical form during photosynthesis.The energy stored in food or green plants is consumed by the plant eaters (herbivores) which make the second trophic level. Herbivores are also called primaryconsumers. Primary consumers in turn are eaten by carnivores (also known as secondary consumers) which occupy third trophic level. Secondary consumers (Primary carnivores) may be eaten by other carnivores (secondary or top carn ivores) which are known as tertiary consumers and occupy fourth trophic level. Decomposer occupy fifth trophic level in an ecosystem.Food Web- In nature, food chain relationships are very complex. They never operate as isolated sequences, as one organism may form the food source of many organisms and so on. Thus, instead of a food chain, a number of food chains are interconnected with each other and form a web-like structure known as ‘food web'. For example, grass may be grazed by grasshoppers as well as cattle, rabbits and each of these may be eaten by different type of carnivores, such as birds, toads, snakes, foxes, depending on their food habit.Thus, a particular organism may not occupy the same tropic level in every food chain; it may simultaneously behave as secondary, tertiary or a top consumer. Organisms, whose food is obtained from plants by the same number of steps are said to belong to the same tropic level. Thus, green plants occupy the first tropic level or the pr oducer level. The plant grazers occupy the second tropic level or primary consumer or herbivore level (all plant-grazing insects, cattle, deer, rabbits, etc. ).Flesh-eaters, that eat herbivores, form the third tropic level or the secondary consumer or carnivore level-1 (frogs, small fish, etc. ). The third tropic level is the tertiary consumer or carnivore level-2, which eats the flesh of herbivores and secondary consumers. In a similar fashion, tropic levels can be expanded based on the food habits of organisms. Charles Elton, a British ecologist, however, concluded that the number of links in a food chain rarely exceeds five, because in the process of energy transfer there is always the loss of energy to the environment.It is the energy transfer mechanism which determines the number of links in a food chain. Man and many other animals who are omnivores occupy different tropic levels in food chains in relation to pure carnivores. The food web maintains the stability of the eco-syst em. For example, green land can be grazed by different organisms like insects, rabbits, rodents, etc. The insects then can be eaten by frogs which can be eaten by snakes. Snakes can either be eaten by hawks

Anne Hutchinson Essays - American Political Philosophy, Free Essays

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