Environmental Science / Unit 4: Populations
4.3 Limiting Factors and Carrying Capacity
Notes
Limiting factors keep populations from growing indefinitely.
- Density-dependent factors have a stronger effect when the population is dense: competition, predation, disease, and parasites.
- Density-independent factors affect a population regardless of its size: hurricanes, floods, wildfires, droughts, and pollution events.
- Carrying capacity can change when conditions change (a drought lowers it).
- Predator-prey cycles occur when predator numbers rise and fall slightly after prey numbers.
- Example: a disease spreads faster in a crowded herd than in a small one, so disease is density-dependent.
Practice
Which is a density-dependent limiting factor?
The more crowded the population, the more easily disease spreads.
A severe drought kills 40% of the plants in a field, whether the plants were sparse or dense. This is a:
Its effect does not depend on population density.
A drought reduces the grass in a pasture. What happens to the pasture's carrying capacity for cattle?
Less food means the environment can support fewer animals.
Ready for more? Take the Unit 4 test.