Organisms And Populations

An age pyramid plots the proportion of individuals in pre-reproductive, reproductive, and post-reproductive age groups. A pyramid that is broad at the base and tapers towards the top indicates a very large proportion of young, pre-reproductive individuals, signalling an expanding population that will grow rapidly as these individuals mature and reproduce. A stable population is represented by a bell-shaped pyramid where pre-reproductive and reproductive groups are roughly equal, so that option is incorrect. A declining population shows a narrow base with a relatively broad middle and top, indicating fewer young individuals, which contradicts the broad base described. A reversed sex ratio is not something an age pyramid shape alone conveys, since the pyramid depicts age structure rather than the male-to-female ratio. As described in NCERT Class 12, Chapter 13 (Organisms and Populations), the shape of the age pyramid reflects the growth status of a population. Plausibility check: a wide base means many future breeders, which logically predicts rapid future growth, making the expanding-population interpretation internally consistent.