STD 12 - 11. organisms and populations — BIOLOGY STD 12 Science — Question

d
(d) : Age pyramid is a graphic representation of abundance of individuals of different age groups with pre­reproductive individuals at the base, reproductive individuals in the middle and post­ reproductive individuals at the top. Triangular age pyramid has high proportion of pre­ reproductive individuals, moderate number of reproductive individuals and fewer post­ reproductive individuals. It represents young or rapidly growing population. In bell­shaped age pyramid, the number of pre­reproductive and reproductive individuals is almost equal. Post ­ reproductive individuals are comparatively fewer. It represents stable or stationary population where growth rate is nearly zero. In urn­shaped age pyramid, the number of reproductive individuals is higher than the number of pre­reproductive individuals. It represents declining or diminishing population.