Ecological Tolerance (College Board AP® Environmental Science): Study Guide

What is ecological tolerance?

• Ecological tolerance refers to the range of environmental conditions an organism can endure before experiencing harm or death

• Key environmental conditions include:

  • Temperature

  • Salinity

  • Flow rate

  • Sunlight

  • pH

  • Oxygen levels

  • Nutrient availability

• For example, coral reefs have a narrow tolerance range for temperature; even small increases can lead to bleaching

• Organisms:

  • Thrive within their optimal range

  • Struggle as conditions approach their tolerance limits

  • Cannot survive outside their tolerance limits

Awaiting image: Ecological tolerance
Image caption: Tolerance range graph showing the ecological tolerance of a population of fish

Ecological tolerance of individual organisms & species

Ecological tolerance of individuals

• Each individual organism has a specific range of tolerance influenced by many factors, such its genetics, age, and health

  • Example: Young fish may have a narrower tolerance range for water salinity compared to adults

• Stress outside optimal conditions can reduce reproduction, growth, and survival rates

Ecological tolerance of species

• Tolerance ranges also apply to entire species, shaping their distribution and abundance in ecosystems

  • Generalists tend to have broader tolerance ranges, allowing them to thrive in diverse environments

    • Example: Raccoons can tolerate a wide range of temperatures and food sources

• Specialists often have narrow tolerance ranges and rely on specific conditions

  • Example: Giant pandas depend completely on bamboo forests for food and habitat

Awaiting image: Generalist vs specialist
Image caption: Graphs showing the difference in tolerance ranges for generalist and specialist species

Importance of ecological tolerance

• Ecological tolerance determines how organisms and species respond to environmental changes and disturbances

• It plays a key role in ecosystem dynamics, including competition and habitat selection

  • Example: Climate change can push species beyond their tolerance ranges, leading to shifts in ecosystems, species migrations or species extinction