Environmental resistance refers to:

• A. Factors that increase population growth
• B. The sum of biotic and abiotic factors that limit population growth
• C. A measure of genetic diversity in a population
• D. The rate of reproduction in ideal conditions

Answer: (B)

Environmental resistance is the combined influence of all factors in an environment that limit population growth. This includes biotic factors like predation, disease, competition for resources, and food availability, as well as abiotic factors such as temperature, salinity, oxygen, pH, light, and habitat space. Together these pressures prevent a population from growing unchecked and cause growth rates to slow as resources become scarce or conditions become less favorable, moving the population toward the environment’s carrying capacity. Without these limiting factors, populations would expand rapidly according to their reproductive potential, but the resistive forces in the environment shape the reality of population size. The description fits best because it explicitly accounts for both living and nonliving limiting influences on growth.