Nature of Communities Essay Example for Free

Nature of Communities Essay At the beginning of the 20th century there was much debate about the nature of communities. The driving question was whether the community was a self-organized system of co-occurring species or simply a haphazard collection of populations with minimal functional integration (Verhoef, 2010). Krebs (1972) described a community as an assemblage of populations of living organisms in a prescribed area or habitat. However, according to Wright (1984), the working definitions of community can be divided into two basic categories: organismic or individualistic. The organismic approach contends that communities have discrete boundaries and that the sum of the species in an area behaves as organism with both structure and function. In contrast, the individualistic concept regards communities as collections of species requiring similar environmental conditions (Wright, 1984). A)Organismic versus individualistic distribution Solomon (2005) stated that the nature of communities is discussed based on two traditional views which are Clements’s organismic model and Gleason’s individualistic model. The organismic model views community as a superorganism that goes through certain stages of development (succession) toward adulthood (climax). In this view, biological interactions are primarily responsible for species composition, and organisms are highly interdependent. In contrast, according to individualistic model, abiotic environmental factors are the primary determinants of species composition in a community, and organisms are largely interdependent on each other. According to organismic concept it is expected that an entire community or biome will respond as a unit and to relocate as climatic conditions change. Pleistocene biome migration in response to multiple glaciations, the accordian effect, is a classic example of this model (Wright, 1984). In contrast, Wright (1984) further explained that the individualist expects each species experiencing similar climatic changes to respond independently and thus, the community composition of an area to change via both immigration and emigration of some individual taxa while others remain in the area. Communities are not stable under this model but recognize in response to changing local conditions. According to Clements’ organismic hypothesis, species that typically occupy the same communities should always occur together. Thus, their distributions along the gradient would be clustered in discrete groups with sharp boundaries between groups (Russell et al., 2011). In the 1920s, ecologists; Frederic Clements and Henry A. Gleason developed two extreme hypotheses about the nature of ecological communities (Russell et al., 2011). Clements championed an interactive (organismic) view describing communities as â€Å"superorganism† assemblages of species bound together by complex population interactions. According to this view, each species in a community requires interactions with a set of ecologically different species, just as every cell in an organism requires services that other types of cells provide. In contrast, Gleason proposed an alternative, individualistic view of ecological communities. He believed that population interactions do not always determine species composition. Instead, a community is just an assemblage of species that are individually adapted to similar environmental conditions.According to Gleason’s hypothesis, communities do not achieve equilibrium; rather, they constantly change in response to disturbance and environmental variation. According to Gleason’s individualistic hypothesis, each species is distributed over the section of an environmental gradient to which it is adapted. Different species would have unique distributions, and species composition would change continuously along the gradient. In other words, communities would not be separated by sharp boundaries. B)Stochastic Versus Equilibrium Schools The stochastic school believes that most communities exist in a state of equilibrium, where competitive exclusion principle is prevented by periodic population reductions and environmental fluctuations (Crawley, 1997). More generally, stochastic effects can cause a population to shift from one type of dynamic behavior to another (Turchin, 2003). In addition, stochastic school maintains that physical and temporal factors are dominant influences of community composition. This view argues that species abundance varies and is largely determined by differential responses to unpredictable environmental changes (Levin, 2009). In contrast, the equilibrium explanations assume that community composition represents the stable outcome of interspecific interactions (set of species abundances reached when the rates of change in population is zero) and also assume that the community will return to an equilibrium after those populations are perturbed (Verhoef, 2010). For instance, the traditional equilibrium model assumes that the probability of an individual fish larva surviving to reproduce is limited in a density-dependent manner by the abundance of the adult fish. Alternatively, stochastic model predicts that recruitment to the adult phase is independent of the density of the adults (Chapman et al., 1999). Equilibrium model states that species richness is entirely determined by ongoing immigration and extinction (Kricher, 2011). Therefore, equilibrium model can be said to be deterministic process which is important in shaping community structure through competition and predation on native species over short temporal scales (Thorp et al., 2008). For example, Chapman et al., (1999), stated that coral reefs communities are at equilibrium showing precise resource partitioning in response to the competition between the various fish species. However, in contrast, the community may also be more susceptible to stochastic processes. For example, the number of fish species on coral reefs is kept high largely by stochastic processes. According to Naiman et al., (2001), stochastic processes are unpredictable and operate in a relatively density-independent fashion. This is the opposite of the traditional, equilibrium hypothesis which emphasizes density dependent competition between species.

Global Warming Essay -- Environment Climate Change

Global Warming Human kind has entered a brand new relationship with the earth. The constant and increasing pressures we are exerting threaten our planets ability to sustain life itself. Change-in the way we think , and in the way we live-is needed now.Global warming is the most urgent environmental problem the world will face in the next decade and the next century. Few, if any, trends are more important to our future than climate change caused by human activities. Scientist around the world are warning us that global warming poses a major threat to our future quality of life, previously there has been little information on this problem. Right now, the rate of global warming may be 100 times faster than it has ever been. Very soon the earth may become hotter then at any time in human history. In the last decades the problems of atmospheric change have been gravely advanced by pollution resulting from human activities. These environmental changes pose a real threat to the lives of people and wild life.It is vital to all of us that we fully understand the complex relationship between the atmosphere and the earth. The earth is getting warmer. the changes are small, so far, but they are expected to grow and speed up. Within the next 50 to 100 years, the earth will continue to heat up hotter than it has been in the past million years. As oceans warm and glaciers melt, land and cities along coasts may be flooded. Heat and drought may cause forests to die and food crops t...

Meditation on Yellow by Olive Senior Essay

Olive Senior is a Jamaican poet who explores Caribbean history. Her poetry often conveys her displeasure of colonization and the suffering Caribbean people endured. Meditation on Yellow explores the colonization and exploitation process carried out by the Europeans. This poem strong conveys Senior discontentment as it relates to the exploitation of the land and the Amerindian tribe. It through the use of symbolism, language and repetition the brutality of colonization is conveyed. Symbolism is used to portray the harsh reality of colonization. In Meditation on Yellow â€Å"yellow† is symbolic of the innocence of the Amerindians and the purity in their mind and soul upon encountering the Whites. This is noted in the phrase † but we were peaceful then child-like in the yellow dawn of our innocence.† The fact that these Amerindians had no idea of what was to come their way and that they offered the best of what they had to the Europeans makes this encounter even more sad and advantageous. Furthermore, yellow is symbolic of sickness and infection. This is reflect in the minds of the Europeans as it was infected with the yearning for wealth and power. Due to this â€Å"infection† the Amerindian we turned into slaves, the land was exploited and the Europeans began colonization. The use of symbolism conveys the extremes which these two set of people existed, the Amerindian being kind and pure and the Europeans being cold-hearted and greedy. Senior’s use of language is certainly a powerful tool in expressing her displeasure as it relates to the enslavement of the Amerindians. Throughout the poem she uses sarcasm and humor which highlights her mocking and belittling of the Europeans. The phrase † had I known I would have brewed up some yellow fever grass and arsenic† is an example of sarcasm. In this phrase there is a contrast between the gesture of hospitality of ethnic which is the â€Å"fever grass† and the bitter sinister intentions of k illing the Europeans with the † arsenic poison.† The sarcasm continues in the phrase † despite the differences in our skins, our piss was exactly the same shade of yellow.† This highlights that regardless of ethnic and racial differences we are all the same. The striking, crude comparison stresses the need for equality and for readers to take note. Furthermore Olive Senior educates us that these Amerindian displayed passive resistance as they deliberately burnt the bread of the Europeans since they we treated badly. The phrase † for which management apologizes† certainly indicates they there was no remorse or sorry for these actions. The use of sarcasm highlight Senior’s hatred towards the colonization process and her view on the Europeans. Repetition is also used to place emphasis on the greedy and materialistic nature of the Europeans. This type of repetition is known as anaphora. The line † but it was gold in your mind gold in your eyes gold in the crown .. gold the prize † highlights the obsession these Europeans had with gold and their gluttonous nature. Moreover, their unreasonable wants and desires are also highlighted through repetition. This is noted in the line † want it strong wan it long want it black want it black want it green want it dread.† Additionally there was repetition in the in line † silver was you armor silver the cross of your Lord †¦ silver the bullet I bite†¦Ã¢â‚¬  This repetition emphasizes the many different forms of silver and the destruction that the silver symbolizes . The silver was representative of Iron Age Technology and represents the European’s military superiority over the stone age Amerindians. Collectively the repetition of these lines alerts readers of the suffering these Amerindians endured to please the cold hearted Europeans. The use of these techniques clearly depicts Senior’s displeasure and the unfortunate struggles of colonization.

Resistance and Opposition in the GDR

Even though the authoritarian regime of the German Democratic Republic (GDR) lasted for 50 years, there had always been resistance and opposition. In fact, the history of socialist Germany started out with an act of resistance. In 1953, only four years after its creation, the Soviet Occupiers were forced to take back control over the country. In the Uprising of June 17th, thousands of workers and farmers put down their tools in protest of new regulations. In some towns, they violently drove the municipal leaders from their offices and basically ended the local reign of the â€Å"Sozialistische Einheitspartei Deutschlands† (SED), the GDR’s single ruling party. But not for long. In the larger cities, such as Dresden, Leipzig, and East-Berlin, large strikes took place and workers assembled for protest marches. The Government of the GDR even took refuge to the Soviet Headquarters. Then, the Soviet Representatives had enough and sent in the military. The troops quickly suppressed the uprising by brutal force and restored the SED Order. And despite the dawn of the GDR was coined by this civil uprising and despite there always being some kind of opposition, it took more than 20 years, for the Eastern German Opposition to take a clearer form. Years of Opposition The year 1976 turned out to be a crucial one for the opposition in the GDR. A dramatic incident awoke a new wave of resistance. In protest against the atheist education of the country’s youth and their oppression by the SED, a priest took to drastic measures. He set himself on fire and later died of his injuries. His actions forced the protestant church in the GDR to re-evaluate its attitude towards the authoritarian state. The regime’s attempts to play down the priest’s acts triggered even more defiance in the population. Another singular but influential event was the expatriation of the GDR-Songwriter Wolf Biermann. He was very famous and well-liked both German countries, but had been forbidden to perform due to his criticism of the SED and its policies. His lyrics kept being distributed in the underground and he became a central spokesperson for the opposition in the GDR. As he was allowed to play in the Federal Republic of Germany (FRG), the SED took the opportunity to revoke his citizenship. The regime thought that it had gotten rid of a problem, but it was deeply wrong. Numerous other artists voiced their protest in light of the expatriation of Wolf Biermann and were joined by a lot more people from all social classes. In the end, the affair led to an exodus of important artists, heavily damaging the GDR’s cultural life and reputation. Another influential personality of the peaceful resistance was the author Robert Havemann. Being freed from death row by the Soviets in 1945, at first, he was a strong supporter and even a member of the socialist SED. But the longer he lived in the GDR, the more he felt the discrepancy between the SED’s real politics and his personal convictions. He believed, that everyone should have the right to his own educated opinion and proposed a â€Å"democratic socialism†. These views got him expelled from the party and his ongoing opposition brought him a string of intensifying punishments. He was one of the strongest critics of Biermann’s expatriation and on top of criticizing the SED’s version of socialism, he was an integral part of the independent peace movement in the GDR. A Struggle for Freedom, Peace, and the Environment As the Cold War heated up at the beginning of the 1980s, the peace movement grew in both German Republics. In the GDR, this meant not only fighting for peace but also opposing the government. From 1978 on, the regime aimed at completely imbue the society with militarism. Even kindergarten teachers were instructed to educate the children in vigilance and to prepare them for a possible war. The Eastern German peace movement, that now also incorporated the protestant church, joined forces with the environmental and anti-nuclear movement. The common enemy for all of these opposing forces was the SED and its oppressive regime. Sparked by singular events and people, the opposing resistance movement created an atmosphere that paved the way for the peaceful revolution of 1989.