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

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

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

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.

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

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.

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.

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

Population growth Exponential growth unlimited dN/dt = rN Unrealistic

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

Life History Strategies Fluctuating populations of two interacting populations Based on pelts sold by Canadian trappers to the Hudson Bay Company, ~1840-1940. 02 June 2010 Populations.ppt

Exponential versus Logistic