1. Ecology Notes
Populations – Chapter 5

2. 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)

3. 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

4. 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

5. 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
I=10, N=7, E=8, M=3
Change =+6
Average Annual Change = +6/4yrs.=+1.5 monkeys/year

6. 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.

7. 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

8. Density Independent Factors
A factor that affects all populations in similar ways, regardless of population size.
Unusual weather
Natural disaster
Seasonal cycles
Human activity