Organisms can only live within certain minimum and maximum limits for each abiotic factor. The range between the upper and lower limits is known as the tolerance range for the factor. Death occurs beyond this range. For example, for most animals the minimum temperature limit is 0°C and the maximum limit is 42°C. Their tolerance range is 0 to 42°C. 0°C is known as the lower lethal temperature and 42°C as the upper lethal temperature.
The tolerance range for a given abiotic factor varies from species to species. Within a species too, the tolerance range can vary from population to population, depending on their ecological niches.
Within the tolerance range for each abiotic factor is the optimum range, I.e the range within the species' growth and reproduction are at their peaks. Beyond this range, its life processes cannot function well, I.e. the species face physiological stress. Thus, its growth and reproductive rates fall.
Tolerance range may differ for each abiotic factor. For example, an organism may have a broad range of tolerance for temperature and a narrow one for PH. They may change as an organism passes through the various stages in its life. Usually, the young organism has a narrower tolerance range than the adult. The minimum and maximum limits of tolerance for all abiotic factors may very geographically and seasonally. One factor may affect the tolerance ranges of other factors. For example, when the oxygen level of water is low, lobsters can only tolerate temperatures up to 29°C , but at higher oxygen levels, they can tolerate temperatures up to 32°C.
