Question

How do different age groups influence the population growth? Explain with the help of graphic representation.

Answer 1

Population growth depends on the proportion of individuals in each ecological age group: pre-reproductive, reproductive and post-reproductive.

Effect of age groups

1. Pre-reproductive group (young): Not yet breeding but will add to future births. A large share of young individuals makes the population expand.
2. Reproductive group (adults): Directly responsible for births. Their number determines the current natality rate.
3. Post-reproductive group (old): Do not reproduce and contribute to mortality. A large share makes the population decline.

Types of populations (age pyramids)

Population type	Age structure	Growth status
Expanding	Broad base (many young)	Population increases
Stable	Nearly equal young and old	Population remains constant
Declining	Narrow base, large old group	Population decreases

Graphic representation

The age structure of a population predicts its future growth, so a broad-based pyramid signals rising numbers while a narrow-based pyramid signals decline.