APES 2.4 Ecological Tolerance

Ecological range of tolerance

Range of conditions such as temperature, salinity, pH, or sunlight that an organism can endure before injury or death results

Species and individual organisms

Species and individual organisms both have a range of tolerance for all the different abiotic conditions of their habitat.

Ex: Salmon have a basic range of tolerance for temperature from 6 to 22 C. But some individual salmon have adaptations that give them a range of tolerance that is outside the basic range for the species,

• Due to genetic diversity

• Makes populations of salmon more resistant to disturbances, like global warming

Optimal range

Range where organisms survive, grow, and reproduce

Zone of physiological stress

Range where organisms survive, but experience some stress such as infertility, lack of growth, decreased activity, etc.

Zone of intolerance

Range where the organism will die. Ex: Thermal shock, suffocation, lack of enough light for plants to survive, low soil moisture.

Human activities and climate change

Electricity generation, transportation, and agriculture all release CO₂, which causes climate change and global warming.

Global warming and tree species

Global warming shifts temperature outside the range of tolerance for many tree species, causing their populations to decline.

Global warming and ocean fish

Global warming warms the ocean, shifting temperature outside the range of tolerance for many fish species, causing die-offs.

Warm ocean water and fish

Warm water holds less oxygen, so fish may suffocate due to lack of oxygen.

Drought and plant species

Global warming can increase droughts. With increased droughts, rainfall patterns may shift outside the range of tolerance for many plant species. Without enough rainfall, these species may suffer population decline as their roots are unable to absorb enough water from the soil.