1. Limits to growth
Section 5.2

2. What factors control carrying capacity?
Limiting factor = factor that controls the rate of growth of a population
Examples
Competition
Predation
Parasitism and disease
Unusual Weather
Natural disaster
Can work separately or together – How do they each increase death rate in a population?
Some depend of population density
Limiting factors determine the carrying capacity of a community

3. Density dependent limiting factors
Operate strongly only when population density reaches a certain level
They do not affect small scattered populations as much
Examples:
Competition
Predation
Herbivory
Parasitism
Disease
Stress from overcrowding

4. Competition In crowded populations, organisms compete for
Food
Water
Sunlight
Space
Some organisms obtain enough for themselves
Others enough to reproduce and support a family
Others may starve to death

5. Why is competition density dependent?
The more individuals the sooner they use up available resources
Space and food are often related
If no territory, cannot breed, no offspring
Competition can also occur between different species fighting for the same resources
Driving force for evolution – natural selection

6. Predation and Herbivory
Wolves and moose – page 139

7. Humans as predators
Humans can limit populations due to hunting, fishing,
Example cod – new england
Solution – stop eating cod!

8. Parasitism and disease
Parasites have the power to weaken or kill an organism
Diseases can wipe out entire populations

9. Stress from overcrowding
Some species fight amongst themselves when overcrowded
Fighting can cause stress
This weakens the body and cause females to neglect or even kill offspring

10. Density independent limiting factor
Affect all populations in similar ways regardless of population size and density
Examples
Unusual weather
Natural disaster
Initially after disaster population will crash
Population may regrow quickly, or may take long time

11. Is a freak snow storm a density dependent or density independent limiting factor
Depends on where the population are living? On an island, where emigration is not possible, it becomes a density dependent factor

12. Controlling induced species
Limiting factors in one environment are not always present in the new environment
Herbicides or mechanical removal are often only temporary measures
In Florida – grass carp eat Hydrilla
All introduced grass carp are sterilized – why?