The AJ-curve of population size indicates: a) a decreasing population b) linear growth c) a constant population size d) a population at carrying capacity e) exponential growth

The option d) a population at carrying capacity is correct answer.

The AJ-curve typically represents a population growth curve that has leveled off at the carrying capacity of the environment. Carrying capacity is defined as the maximum number of individuals of a particular species that an environment can support indefinitely. When a population reaches this point, the resources available (such as food, space, and other necessities) are being used at a sustainable rate that matches the population's consumption.

When a population graph shows an S-shaped curve or a sigmoid curve, it represents a pattern of growth where the population size increases rapidly at first, but then the growth rate slows down as the population size approaches the carrying capacity of the environment. The leveling off, or asymptote, of the curve is where the AJ-shape comes into play, indicating that the population has reached a steady state where births plus immigration equal deaths plus emigration.