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 meters2 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