If in a forest there were 570 sambhars last year and through reproduction 30 new sambhars were added, taking the current population to 600. Calculate the birth rate.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 0.052 offsprings per sambhar per year
The birth rate is the number of births per member of the population in a given period.
New sambhars added by reproduction = 30.
Population at the start = 570.
Birth rate = 30 ÷ 570 = 0.0526, i.e. about 0.052 offspring per sambhar per year.
Option (1) 5 offsprings per sambhar per year — Incorrect. It looks like a percentage (about 5%) written as a rate per individual.
Option (2) 0.6 offsprings per sambhar per year — Incorrect. No division of the given numbers gives 0.6; it may come from the current total of 600.
Option (4) 20 offsprings per sambhar per year — Incorrect. 20 is 600 ÷ 30, the division turned upside down.
NCERT Extract:
Population Attributes – “… If in a pond there were 20 lotus plants last year and through reproduction 8 new plants are added, taking the current population to 28, we calculate the birth rate as 8/20 = 0.4 offspring per lotus per year. If 4 individuals in a laboratory population of 40 fruitflies died during a specified time interval, say a week, the death rate in the population during that period is 4/40 = 0.1 individuals per fruitfly per week.”