2.4

Range of Tolerance: Populations thrive within certain ranges of abiotic factors such as pH, temperature, light, amount of moisture, etc.

• Different organisms have different ranges, such as with temperature

• An organism’s tolerance may change over its lifetime, such as salmon with salinity

Limiting factors: The environmental factor that is most often in short supply

• Even if all the other factors are optimum, it’s the one most likely to regulate population growth

• important limiting factors

  • Soil: Often nitrogen, phosphorus, or potassium—this is why NPK testing kits are used and why those nutrients are components of fertilizers

  • Open Ocean: Sometimes nitrogen, silica or iron; sometimes dissolved oxygen (DO)

  • Freshwater Lakes and Rivers: Often phosphorus

  • Bays and estuaries: Salinity

2.5

Resistance: Ability to remain unchanged when being subjected to disturbance

Resilience: Ability and rate of an ecosystem to recover from a disturbance and return to its pre-disturbed state

INTERMEDIATE DISTURBANCE HYPOTHESIS:

Ecosystems require a certain level of disturbance for maximum health and diversity

• ex: intertidal zone