In-Depth Notes on Ecological Tolerance

Range of Tolerance

  • Concept Overview

    • The range of tolerance refers to the conditions that a species can endure, including both abiotic (non-living) and biotic (living) factors.
    • Within this range, species show varying abilities to survive and reproduce, depending on environmental conditions.

  • Key Zones in Range of Tolerance

    • Zone of Intolerance

    • Conditions are too extreme for any individuals to survive.

    • Referred to as the limits of tolerance (upper and lower limits).

    • Zone of Physiological Stress

    • Organisms may survive but exhibit stress, potentially affecting growth and reproduction.

    • This zone indicates a less favorable environment.

    • Optimum Range

    • The conditions where a species thrives best and exhibits the greatest abundance and fitness.

  • Organisms and Their Tolerance

    • All organisms have specific tolerance ranges, including microbes, fungi, plants, and animals (including humans).
    • Different species have different requirements: some thrive in bright sunlight while others prefer shade, or some need wet conditions while others do better in dry conditions.

  • Human Impact on Tolerance

    • Although technology enables humans to adapt to extreme environments, they have limits and can still succumb to extreme conditions (e.g., freezing temperatures, heatstroke).
    • Our technological advancements only mitigate, but do not remove, vulnerabilities to environmental stresses.

  • Factors Influencing Tolerance

    • Abiotic Factors

    • Important non-living determinants include:

      • Light
      • Temperature
      • Humidity
      • Soil chemistry (pH, salinity)
      • Oxygen levels
      • Nutrient availability

    • Biotic Factors

    • Factors involving living organisms such as:

      • Predation
      • Competition
      • Parasitism
      • Herbivory

  • Population Variability in Tolerance

    • Within a population, individuals may display variations in tolerance ranges due to genetic makeup, health, and age.
    • Example: Fish within a specific population might thrive in a narrow temperature band, but some may survive extreme conditions momentarily; if temperatures exceed tolerance, all members will perish.

  • Conclusion

    • Understanding the range of tolerance is crucial for predicting how species will respond to environmental changes and for conservation efforts.
    • Ecological tolerance is not only important for species but applies to individual organisms within specific ecosystems.