UNIT 3.4 ~ Carrying Capacity
Carrying Capacity (k):
- the max. Number of individuals in a pop. that an ecosystem can support (based on limiting resources)
Carrying Capacity (k)
- Highest pop. size an ecosystem can support based on limiting resources:
- Food
- Water
- Habitat (nesting sites, space)
- Overshoot:
- when a population briefly exceeds carrying capacity
- Ex: deer breed in fall, give birth all at once in spring; sudden spike in pop. = overshoot
- Consequence of overshoot:
- resource depletion ex: overgrazing in deer
- Die-off:
- sharp decrease in pop. size when resource depletion (overshoot) leads to many individuals dying
- Ex: many deer starve with too many new fawns feeding in spring
Die-off Example
- Reindeer of St. Paul Island
- 25 introduced in 1910
- Growth was gradual (10’-30’), then exponential (30’-37’)
- Carrying capacity was overshot
- Sharp die-off lead to pop. crash as food resource (lichen) were severely depleted
- Real pops. don’t always fluctuate around carrying capacity. If resource depletion is severe enough, total pop. crash can occur
Predator-Prey
- Hare pop. increase due to low predator pop. (lynx)
- Lynx pop. increase due to increase in food (hare)
- Increasing lynx pop. limits hare pop; leads to die-off
- Hare die-off decreases lynx food source, leading to die-off
- Hare pop. increase due to low predator pop. (lynx)