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Ecology Notes Populations – Chapter 5
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Characteristics of Populations Population – group of individuals of the same species that live in the same area. Population – group of individuals of the same species that live in the same area. –1. geographic distribution – the area inhabited by a population (range)
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Population Density 2. density – number of individuals per unit area. Area = L X W Area = 2m X 1m Area = 2 meters 2 Population Density = # individuals/area Population Density = 6/2 = 3 rabbits per square meter 1 meters 2 meters
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3. Growth – populations may stay constant or change drastically from year to year. 3. Growth – populations may stay constant or change drastically from year to year. 4 factors affect population size 1. Natality – birth rate 2. Mortality – death rate 3. Immigration – movement of individuals IN 4. Emmigration – movement of individuals OUT
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Average Annual Change The average rise or fall in a population per year. Can be positive or negative The average rise or fall in a population per year. Can be positive or negative Formula A.A.C.= change in pop./years Formula A.A.C.= change in pop./years Sample Problem Sample Problem What is the average annual change of this monkey population? 2001 – Rainforest 125 monkeys 2001-2005 I=10, N=7, E=8, M=3 Change =+6 Average Annual Change = +6/4yrs.=+1.5 monkeys/year
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Exponential vs. Logistic Growth Exponential growth – population grows at a constant rate…with unlimited resources this will occur. Exponential growth – population grows at a constant rate…with unlimited resources this will occur. Logistic Growth- occurs when growth slows or stops. The largest number of individuals the environment can support is called the carrying capacity. Logistic Growth- occurs when growth slows or stops. The largest number of individuals the environment can support is called the carrying capacity.
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Limiting Factors Limiting factors cause population growth to decrease. Limiting factors cause population growth to decrease. –Density dependent – a factor that depends on population size. Occurs when populations are large and dense. Competititon Predation Parasitism Disease
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Density Independent Factors A factor that affects all populations in similar ways, regardless of population size. A factor that affects all populations in similar ways, regardless of population size. –Unusual weather –Natural disaster –Seasonal cycles –Human activity
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