Question

Given below are typical age-structure diagrams. Choose the appropriate explanation for each age structure pyramid.

• A. 1.Expanding rapidly
  2.Expanding slowly
  3.Stable
  4.Declining
• B. 1.Declining
  2.Stable
  3.Expanding slowly
  4.Expanding rapidly
• C. 1.Stable
  2.Declining
  3.Expanding rapidly
  4.Expanding slowly
• D. 1.Expanding slowly
  2.Expanding rapidly
  3.Declining
  4.Stable

Answer 1

The correct option is A 1.Expanding rapidly
2.Expanding slowly
3.Stable
4.Declining

In an age structure diagram, depending on the number of individuals in each age class we can determine whether a population is expanding, stable or declining. The shape of the pyramid predicts the future growth of the population. Age pyramids with a broader base, i.e. large number of individuals in the pre-reproductive and reproductive stages indicate an expanding population. This pattern is usually seen in developing countries.
Populations in which the number of individuals are almost similar in pre-reproductive and reproductive stages, expands slowly. When the number of individuals are more or less equal in all age classes, it indicates a stable population. When the base of the pyramid is narrow with lesser pre-reproductive individuals than post-reproductive individuals, it indicates a declining population.
Declining population is a population, which has higher death rate than birth rate, because majority of the population are in the post-reproductive, old age, than in the reproductive or pre-reproductive phase, where they can soon reproduce.