| Cue Column | Notes Column |
|---|---|
| 5 population attributes | Density (N) — individuals per unit area/volume; Natality (b) — birth rate; Mortality (d) — death rate; Sex ratio — males:females; Age distribution — proportion in each age class |
| How to measure N? | Quadrat method (sessile organisms); Mark-recapture method (mobile organisms) — N = |
| Formula for r | r = b - d (intrinsic rate of natural increase). r > 0 = growing; r = 0 = stable; r < 0 = declining |
| Three age pyramid types | Expanding — broad base (many young); Stable — uniform shape (equal age groups); Declining — narrow base (few young, many old) |
| Sex ratio effect | More reproductive females → higher natality → faster population growth |
| NEET application | Mark-recapture formula: N = (marked released × total recaptured) / marked in recapture sample |
Summary: Population size is shaped by five interacting attributes. The age pyramid provides a visual snapshot of population trajectory — broad base = growing, narrow base = shrinking.