Identify the ecological age groups that populations can be categorise…

The correct answer is Option (1) → I, II and III

The age distribution of a population is shown as an age pyramid. Its bands sort individuals by their stage of reproductive life into three ecological age groups: pre-reproductive, reproductive and post-reproductive. The shape of the pyramid shows whether the population is expanding, stable or declining.

I - Age group before reaching reproductive maturity. — True. This is the pre-reproductive group, the base of the pyramid.

II - Age group capable of reproduction. — True. This is the reproductive group, the middle bands.

III - Age group after the reproductive phase. — True. This is the post-reproductive group, the top of the pyramid.

IV - Infertile age group. — False. There is no separate “infertile” group. Individuals that do not reproduce are already placed in the pre-reproductive or post-reproductive group, so the three groups above are the only ecological age groups.

Note: Pre-reproductive, reproductive and post-reproductive are printed only as labels on Figure 11.1, not in the running text. Figure labels are part of the syllabus too, so read them as closely as the paragraphs.

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