Definition - What does Tolerance Limits mean?
Tolerance limits consist of the the upper and lower limits of a particular environmental condition which allows a certain species to survive. Environmental conditions can include the amount of water, temperature, light, or the availability of other resources. Creatures that have a greater range of tolerance can survive in a larger area and are more widely distributed. Creatures with a smaller range are often less widely distributed.
Safeopedia explains Tolerance Limits
The different species on our planet are found in different areas and have their own set of environmental conditions in which it can survive. The outer limits of these conditions are where they start to change and the species begins to lose it's ability to survive once it is outside these tolerance limits. Some of these conditions can overlap with that of other species. The largest influencing factor is usually temperature.