If in a pond there were 150 carps found last year and through reproduction 450 new carps are added in the pond, what will be the birth rate here?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 3 offsprings per carp per year
The birth rate of a population is the number of births per member of the population in a given time.
Birth rate = number of new individuals ÷ size of the population
= 450 ÷ 150
= 3 offspring per carp per year
Option (1) 4 offsprings per carp per year — Incorrect. This divides the new total (600) by 150; the birth rate counts only the births.
NCERT Extract:
Population Attributes – “… A population has certain attributes whereas, an individual organism does not. An individual may have births and deaths, but a population has birth rates and death rates. In a population these rates refer to per capita births and deaths. The rates, hence, expressed are change in numbers (increase or decrease) with respect to members of the population. Here is an example. 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.”