Ecology Notes

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Ecology Notes

Populations – Chapter 5

Characteristics of Populations

Population – group of individuals of the same species that live in the same area.

– 1. geographic distribution – the area inhabited by a population (range)

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

 3. Growth – Constant or Change drastically 4 factors affect population size 1. Natality – birth rate 2. Mortality – death rate 3. Immigration – individuals IN 4. Emmigration – individuals OUT

Average Annual Change

   The average rise or fall in a population per year. Can be positive or negative Formula A.A.C.= change in pop./years 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

Exponential vs. Logistic Growth

  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.

Limiting Factors

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

Density Independent Factors

 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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