What do tolerance limits refer to in biology?

Tolerance limits in biology refer to the range of environmental conditions—such as temperature, humidity, pH, and availability of resources—within which an organism can survive, grow, and reproduce effectively. These limits define the boundaries beyond which the organism may experience stress, poor health, or even death. Each species has distinct tolerance limits that contribute to its ecological niche and distribution, determining where it can live and thrive.

Understanding tolerance limits is fundamental for studying organismal biology, ecology, and conservation, as it helps predict how species might respond to environmental changes or stressors. This concept contrasts with other biological ideas, such as population dynamics or growth rates, which focus on different aspects of an organism's biology or its interaction with the ecosystem. For instance, average size and weight, ecosystem carrying capacity, and growth speed are important ecological and biological measures but do not specifically address the critical aspect of environmental conditions needed for survival.