In a country, at any time, the population has the same number of youngs and mature ones. What type of growth does it reflect?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Stable
Option (1) Expanding — Incorrect. An expanding population has a broad base: many more young (pre-reproductive) individuals than mature ones. As the young grow up, the population keeps growing.
Option (2) Declining — Incorrect. A declining population has fewer young than mature individuals. Its base is narrow, so fewer individuals will join the reproductive group later.
Option (3) Stable — Correct. When the young and the mature groups are about equal in number, the young only replace the adults, so the size of the population stays about the same.
Option (4) S-shaped — Incorrect. S-shaped (sigmoid) is a growth curve: logistic growth, in which a population levels off at the carrying capacity. It shows the change in numbers over time, not the age structure of a population.
NCERT Extract:
Population Attributes – “… A population at any given time is composed of individuals of different ages. If the age distribution (per cent individuals of a given age or age group) is plotted for the population, the resulting structure is called an age pyramid (Figure 11.1). For human population, the age pyramids generally show age distribution of males and females in a diagram. The shape of the pyramids reflects the growth status of the population - (a) whether it is growing, (b) stable or (c) declining.”
Figure 11.1 Representation of age pyramids for human population