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How Populations Grow

How Populations Grow - How Populations Grow How Populations...

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Unformatted text preview: How Populations Grow How Populations Grow Three Things That Affect Three Things That Affect Population Growth Number of Births Number of Deaths Migration Movement of animals from one place to another Types of Migration Types of Migration Emigration Movement of individuals out of an area Immigration Movement of individuals into an area occupied by an existing population Equation for Population Growth Equation for Population Growth Birth Rate + Immigration – Death Rate ­ Emigration When individuals in a population grow at a constant rate Example: When a population has unlimited resources Population size Exponential Growth Exponential Growth Time Limiting Factors Limiting Factors A condition that causes the growth of a population to decrease Examples: predation, disease, natural disasters, food shortages, etc. Carrying Capacity Carrying Capacity Largest number of individuals in a population that a given environment can support Logistic Growth Logistic Growth When a populations growth rate stops or slows after a period of K exponential growth Example: Logistic Growth Curve dN K + N = r N dT K K = carrying capacity of environment When a population reaches carrying capacity Optimal yield (= 1/2 K) Time (t) Comparing Exponential and Comparing Exponential and Logistic Growth Limits to Growth Limits to Growth Limiting Factor: any factor that limits the size of a population Examples: Predation, disease, natural disasters, food shortage, etc. Population Density Population Density Number of a particular organism per a specific area Examples: # of deer in a 1 acre forest # of people in Bloomington­Normal # of students in this classroom Density­Dependent Factors Density­Dependent Factors A limiting factor that depends on a populations size Examples: Competition Predation Parasitism and Disease Competition Competition When two organisms compete over the same limited resource Predation Predation When one organism captures and feed on another organism Parasitism and Disease Parasitism and Disease When a parasite or disease needs close contact to be spread from organism to organism West Nile Disease Density­Independent Factors Density­Independent Factors A limiting factor that affects a population in similar ways regardless of the population’s size Examples: Weather (Seasonal Cycles) Human Activities Natural Disasters Weather (Seasonal Cycles) Weather (Seasonal Cycles) Extreme Cold or Heat Winter Frost Heavy Rainfall Human Activities Human Activities Deforestation Hunting Buildings and Roads Natural Disasters Natural Disasters Hurricanes, Tornados, Flooding Earthquakes, Mudslides, Forest Fires ...
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