Final answer:
If the environment changes significantly or a population size is too small, the ability to evolve decreases due to reduced genetic diversity. The population becomes more vulnerable to threats and may be unable to adapt, increasing the risk of decline or extinction.
Step-by-step explanation:
If the environment is changed too much or the population is too small, then the ability of evolving would decrease because the genetic diversity would be reduced too much. Numerous factors can impact a population's ability to evolve, including environmental pressures, and the size and genetic variability of the population. For instance, if environmental changes are rapid and significant, or if a population is too small, there may not be enough genetic variations for natural selection to act upon, leading to a decreased ability to adapt to new conditions. A decline in genetic diversity may make a population more vulnerable to diseases or changing environmental conditions, and they may be less able to respond effectively to these changes.
In nature, environmental limits such as food availability, predation, and other ecosystem changes affect the way organisms grow. If a population's genetic variation is lessened due to a small initial population size or drastic environmental shifts, the population's evolutionary potential diminishes. Consequently, these factors increase the risk of population decline or extinction.
This can be associated with various outcomes, such as decreased life spans of individuals within the population, an increased chance of offspring dying, and decreased chances of mating between individuals, all of which contribute to the potential inability of a population to sustain itself.