1. POPULATIONS , LIMITING FACTORS & CARRYING CAPACITY
Chapter 5
p.130 – p.146

2. Population
number of individuals of a species in a defined place and time.
02 June 2010
Populations.ppt

3. Changes in populations
Growth
Decline
May affect size, density, dispersion, age distribution.
May be affected by size, density, dispersion, age distribution.
02 June 2010
Populations.ppt

6. Density-Dependent Limiting Factors
Density-dependent limiting factors, include competition, predation (Predator/Prey), herbivory (effect of herbivores on the plants), parasitism, disease, and stress from overcrowding.
These do not affect small and scattered populations as much.

7. Population Limiting Factors
Population Ecology: Density-dependent factors
Population Limiting Factors
Density-dependent factors
Any factor in the environment that depends on the number of members in a population per unit area
Usually biotic factors
These include
Predation
Disease
Parasites
Competition

8. Density-Independent limiting factors
Unusual weather such as hurricanes, droughts, or floods and natural disasters such as wildfires, can act as density-independent limiting factors.
These tend to affect all populations regardless of size and density.

9. Population Limiting Factors
Population Ecology: Density-independent factors
Population Limiting Factors
Density-independent factors
Factors that limit population size, regardless of population density.
These are usually abiotic factors
They include natural phenomena, such as weather events
Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.

10. Dynamic characteristics of populations
Size, number of individuals (N)
Density (N/ area)
Dispersion,
Random, uniform, clumped,
(appropriate scale)
02 June 2010
Populations.ppt

11. Population growth
Exponential growth unlimited
dN/dt = rN
Unrealistic

12. Population growth Logistic growth, dN/dt = rN (1 - N/K)
N = number, population size
r = biotic potential, “intrinsic rate of increase.”
K = carrying capacity
Better represents real populations

13. Life History Strategies
Fluctuating populations of two interacting populations
Based on pelts sold by Canadian trappers to the Hudson Bay Company, ~
02 June 2010
Populations.ppt

14. Exponential versus Logistic