Question

In population, the per capita birth rate is 0.15 and the per capita death rate is 0.08 during the unit time period. What is the value of ‘r’?
A) 0.25
B) 0.07
C) 0.05
D) 0.25

Answer 1

Hint: In a population, the rates of births and deaths have to be monitored in proper time intervals. Birth rate or natality is the number of births per 1000 people per year. Death rate or mortality is the number of deaths per 1000 people per year.

Complete answer:
The component ‘r’ is the intrinsic rate of natural increase. It can be understood as the rate with which there is an increase in the population size in the absence of any density- dependent forces in population regulation. It is the difference between birth and death rates during a given unit time period.
Thus, $ r= \text {Birth rate} - \text{Death rate}$
 $ r = 0.15 – 0.08$
Therefore, r = 0.07

Considering the other given options:
A. 0.25 is not the value of ‘r’ since it isn’t value obtained on calculating the difference between the given birth and death rates. Thus it is not the right option.
C. 0.05 is not the value of ‘r’ since it isn’t value obtained on calculating the difference between the given birth and death rates. Thus it is not the right option.
D. 0.25 is not the value of ‘r’ since it isn’t value obtained on calculating the difference between the given birth and death rates. Thus it is not the right option.

Thus the correct answer is option ‘B’.

Note: In a population Growth rate can be identified as the difference observed between birth and death rates. A population grows or the growth rate is positive if the birth rate is greater than death rate. A negative growth rate is observed when the death rate is greater than birth rate.