2.4-2.5 Tolerance and Limiting Factors/ Natural Disruptions to Ecosystems

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

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