Final answer:
Stage 3 of the Timmonds Model represents a stable population structure, with balanced birth and death rates. Stage 4 is characterized by low birth rates, low death rates, and a stable population size.
Step-by-step explanation:
Stage 3 of the Timmonds Model refers to a stable population structure. In this stage, the birth rate and death rate are relatively balanced, resulting in a gradual decrease in the number of individuals per age group, followed by an increase for the older part of the population.
Age structure diagrams for rapidly growing, slow growing, and stable populations are shown in stages 1 through 3. Stage 4 in the Timmonds Model represents a population change that is characterized by low birth rates, low death rates, and stable population size.