The Living World – Part 3

AP Env Sci 2011-2012

Abiotic Factors

• Conditions: abiotic factors that vary in space and time but are not used up or made unavailable to other species

• Temperature, pH, wind, salinity….

• Resources: factors that are consumed

• Water, nutrients, oxygen, space…

Survival Curve

Organisms Respond to Abiotic Factors

• Optimum: for every factor, there is a level at which organisms do best.

• Range of Tolerance: entire span that allows any growth at all.– Limits of tolerance– Zones of stress

• Individuals Population

Law of Limiting Factors (Liebig)• If any one factor (abiotic or biotic) is outside the

optimal range, there will be stress– Places Limits on:

• Growth• Reproduction• Perhaps species survival

– Garden Examples: can you think of any?

– Might be too much or too little

– Could be synergistic effects

Identifying Limiting Factors

• Mice • Montgomery

3 Scenarios: Ecosystems Under Stress:

1. All producers killed by toxic discharge to soil.

2. All parasites eliminated by “miracle” drug.

3. Decomposers wiped out by virus.

What would happen to the ecosystem in each case?