2.5 - natural disruptions to ecosystems

AP Environmental Science: Unit 2 – The Living World: Biodiversity

Topic: 2.5 Natural Disruptions to Ecosystems

Change is a Constant (Page 1)

  • Constant Changes in Ecosystems

    • Earth experiences ongoing changes due to species interference and life cycles.

    • Changes can be:

      • Slow and Evolving: Gradual shifts in ecosystems.

      • Fast and Sporadic: Sudden events causing immediate impact.

      • Intermediate: Changes that fall between slow and fast.

  • Effects of Changes

    • Can be drastic or negligible depending on the ecosystem.

    • May have short-term or long-term effects.

  • Types of Disruptions

    • Natural Disasters: Such as cold weather causing migrations (e.g., geese moving south).

    • Manmade Disasters: Examples include climate change and anthropogenic sea level rise leading to flooding in coastal areas.

Resistance and Resilience

  • Resistance

    • Definition: Measurement of how much an ecosystem changes after a disruption (e.g., forest fire, invasive species).

    • High resistance indicates stability; the ecosystem withstands disturbances with minimal internal damage.

  • Resilience

    • Definition: Measure of how quickly an ecosystem can recover from disturbances.

    • Indicates the ecosystem's ability to rebuild and restore its environment.

Intermediate Disturbance Hypothesis (Page 2)

  • Species Diversity and Disturbance

    • Maximum species diversity occurs at intermediate levels of disturbance.

    • Both early and late succession species can coexist.

  • Succession Species

    • Early Succession Species: Pioneer species that colonize areas quickly after disturbances; require fewer nutrients and face less competition.

    • Late Succession Species: Thrive in mature ecosystems; adapted to stable conditions.

  • Impact of Disturbance Levels

    • Moderate disturbances allow for the best survival of all succession levels.

    • Species diversity is highest at intermediate disturbance levels, while it decreases with low or high disturbance levels.

Key Terms to Review (Page 3)

  • Anthropogenic: Environmental changes caused by human activities (e.g., pollution, deforestation).

  • Early Succession Species: Pioneer species that rapidly colonize disturbed areas.

  • Ecosystem Resilience: Ability of an ecosystem to recover from disturbances.

  • Ecosystem Resistance: Ability of an ecosystem to withstand disturbances without significant changes.

  • Intermediate Disturbance Hypothesis: Suggests moderate disturbances promote higher biodiversity.

  • Late Succession Species: Organisms that thrive in stable, mature ecosystems.

  • Sea Level Rise: Increase in ocean height due to global warming and melting glaciers