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Applications of Biology is most interesting course. Its specialty is, its interesting fro everyone. This lecture also describes some applications. It includes: Populations, Same Members, Species Living, Same Place, Properties of Populations, Density, Dispersion, Even, Clumped, Random
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Three factors can affect population size: the number of births, the number of deaths, and the number of individuals that enter or leave the population.
The J-shaped curve indicates that the population is undergoing exponential (eks-poh-NEN-shul) growth. Exponential growth occurs when the individuals in a population reproduce at a constant rate.
Exponential Growth In the presence of unlimited resources and in the absence of predation and disease, a population will grow exponentially. Both of these hypothetical graphs show the characteristic J-shape of exponential population growth.
Density-dependent limiting factors include competition, predation, parasitism, and disease.
Density-independent limiting factors affect all populations in similar ways, regardless of the population size. Unusual weather, natural disasters, seasonal cycles, and certain human activities—such as damming rivers and clear-cutting forests—are all examples of density-independent limiting factors. In response to such factors, many species show a characteristic crash in population size. After the crash, the population may soon build up again, or it may stay low for some time.
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Wolf and Moose Population The relationship between moose and wolves on Isle Royale illustrates how predation can affect population growth. In this example, the moose population was also affected by changes in food supply, and the wolf population was also affected by disease. Interpreting Graphics How are the increases and decreases in the moose population related to the changes in the wolf population?