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Population Density
The number of individuals per unit area.
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What are 3 characteristics of a population?
Its geographic distribution, density, and growth rate.
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What are 3 factorsthat can affect population size?
The number of births, the number of deaths, and the number of individuals that enter or leave the population.
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Immigration
The movement of individuals into an area, which can cause a population to grow.
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Emigration
The movement of individuals out of an area, which can cause a population to decrease in size.
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Exponential Growth
Occurs when the individualsin a population reproduce at a constant rate. A J- shaped curve shows exponential growth over time!!!!!
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Exponential Growth
Under ideal conditions with unlimited resources, a population will grow exponentially.
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Logistic Growth
Occurs when a population's growth slows or stops following a period of exponential growth.
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Logistic Growth
As resources become less available, the growth of a population slows or stops.
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Carrying Capacity
The horizontal line through the region of the graph where the growth has leveled off.
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Limiting Factor
A factor that causes population growth to decrease.
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Density-dependent limiting factor
A limiting factor that depends on population size. Density-dependent factors become limiting only when the population density-the number of organisms per unit area-reaches a certain level.
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Predator-prey relationship
Populations in nature are often controlled by predation. The regulation of a population by predation takes place within a predator-prey relationship.
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Density-independent limiting factors
Affect all populations in similar ways, regardless of the population size.
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Density-independent limiting factors
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.
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