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An account of factors affecting population density

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An account of factors affecting population density A population is defined as the number of organisms of one species living in a defined area. The population density can be affected by many factors such as competition for resources, disease, migration and gestation period. This can be summarized in four key points: Organisms immigrate to a defined area which increases the population density or organisms emigrate from a defined area which decreases the population density in the defined area but consequentially increases the population density of the area the organisms have migrated too. On the other hand natality and mortality affect the population density in a similar fashion. A high birth rate will increase the population but a high death rate simultaneously will decrease the population density. Growth curves enable you to view how the population density of an organism varies. ...read more.


The carrying capacity is the upper limit in the site of population that the environment can sustain. A density dependent growth is when the density of the population itself is affecting the growth rate and the population oscillates around the carrying capacity. Examples of density dependent factors are food, light, water and competition. Organisms themselves act as density dependent factors regulating the population size. Density independent growth curves show an exponential curve which stops abruptly as the environmental resistance becomes suddenly effective. The growth rate is not determined by the population density itself but of factors such as a sudden drop of temperature, a fire or pesticide. Intra-specific competition is the competition between individuals of the same species and creates a cycle in the population density. Abundant food results in a high feeding rate, immigration and successful reproduction, which in turn results in numbers increasing rapidly. ...read more.


Predation causes increased mortality among prey and prey numbers decline, which subsequently means that predators emigrate, find new prey species or stave. This means that there is a reduced mortality of prey so their density increases and the cycle begins again. The population density of the prey species rises first followed by that of the predator. As the predator population rises it begins to limit the prey population which then also falls. As habitats become more complex the population density increases which leads to a natural emigration of prey from the defined area. With no sediment involved in the cycle it results in both population crashing as there is nowhere for the prey to hide so the predators have an advantage, consume the prey and then have a poor numbers of prey to feed on so starve or emigrate. Many factors affect population density, which results in the population density constantly varying. Rebecca Winter 13S ...read more.

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