Key differences, features, and comparative analysis of Measure and When to use it.
| Measure | When to use it | NCERT example |
|---|---|---|
| Total number | Default; countable populations | Cormorants in a wetland |
| Per cent cover / biomass | When "number" is meaningless — a few huge organisms vs many tiny ones | 200 carrot grass (Parthenium hysterophorus) plants vs 1 huge banyan with a large canopy |
| Biomass / optical density | When counting is impossible or too time-consuming | A dense laboratory culture of bacteria in a petri dish |
| Relative density | When absolute density is not needed | Number of fish caught per trap in a lake |
| Indirect estimation | When the animal cannot be seen/counted | Tiger census from pug marks and faecal pellets |
This comparison table is part of the chapter notes for Organisms and Populations. Get complete notes, flashcards, active recall sheets, and test prep modes: