Ecology 10: Population Dynamics
Population – group of individuals of the same species living in the same area
ex. Trees in a forest
What kind of relationships do organisms in one population have with each other?
- Compete with each other
What factors might change the size of a population?
- Space limitations
Density Independent Factors
*Birth rate and death is not affected by density
*usually caused by changes in abiotic environment
Ex. Tornados, Climate
Density Dependent Factors
*Death rate increases, birth rate decreases as density increase – negative feedback
*usually biotic factors
*Extrinsic Factors: limiting resources, limited space, predators
* Intrinsic factors : hormonal change studied in rodents – aggressive behavior in rodents, delay in
Fecundity – the number of birth of females
Isopods live in decomposing logs, and are prone to desiccation in the summer, and cold in winter
Third year ecology students used Mark and Recapture methods to estimate the population size of
isopods in Totem Field.
1. Density affects their ability to survive because they have less resources available to them in a
Relationship to k
Density dependent factors define carry capacity (k)
Depends on: 1.Quality of habitat 2. Time 3. Characteristics of species
Intrinsic rate of increase r (max)
Genetically determined but can vary with environment
Ex. European lizard – at lower elevation begin breeding younger than at higher elevation.
Therefore r maxC