Statement I: In India, the tiger census in national parks and tiger reserves is often based on pug marks and faecal pellets.
Statement II: Where there are 200 carrot grass (Parthenium hysterophorus) plants but only a single huge banyan tree, per cent cover or biomass is a more meaningful measure of the banyan’s population size than the number of individuals.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both statements I and II are correct.
Population density is the size of a population in an area. The total number of individuals is the usual measure, but it is not always possible or sensible to count every one. Then the size is estimated indirectly, or another measure such as per cent cover or biomass is used.
Statement I: In India, the tiger census in national parks and tiger reserves is often based on pug marks and faecal pellets. — True. Tigers are hard to see and count directly. So their numbers are estimated indirectly from pug marks (footprints) and faecal pellets (the book spells it “fecal”). The book calls these “our” national parks and tiger reserves, that is, in India.
Statement II: Where there are 200 carrot grass (Parthenium hysterophorus) plants but only a single huge banyan tree, per cent cover or biomass is a more meaningful measure of the banyan’s population size than the number of individuals. — True. By number, one banyan against 200 carrot grass plants looks unimportant. Yet the single tree, with its large canopy, has an enormous role in that community. Per cent cover or biomass shows that role, so it is the better measure here.
NCERT Extract:
Population Attributes – “… In an area, if there are 200 carrot grass (Parthenium hysterophorus) plants but only a single huge banyan tree with a large canopy, stating that the population density of banyan is low relative to that of carrot grass amounts to underestimating the enormous role of the Banyan in that community. In such cases, the per cent cover or biomass is a more meaningful measure of the population size. … We are mostly obliged to estimate population sizes indirectly, without actually counting them or seeing them. The tiger census in our national parks and tiger reserves is often based on pug marks and fecal pellets.”