At $N_1$, the population is declining because small populations suffer from low genetic diversity; at $N_2$, the population is growing exponentially because birth rate and death rate are balanced; at $N_3$, the population is stable because density-independent factors regulate growth.

At $N_1$, the population is growing rapidly because birth rate is at its minimum value; at $N_2$, the population is declining because carrying capacity has been exceeded; at $N_3$, the population size is stable because reproduction has ceased due to intense competition.

At $N_1$, the population is increasing because birth rate exceeds death rate, and density-dependent limiting factors are weak; at $N_2$, the population size is stable because birth rate equals death rate, representing carrying capacity ($K$); at $N_3$, the population is decreasing because death rate exceeds birth rate due to intense intraspecific competition.

At $N_1$, the population size is stable because intraspecific competition is absent; at $N_2$, the population is undergoing a sudden crash because death rate is at its maximum; at $N_3$, the population is increasing because high population size stimulates carrying capacity.