Question

The vital index means
A. $Natality\times Mortality$
B. $\cfrac { Natality\times Mortality }{100}$
C. $Natality\quad -\quad Mortality$
D. $\cfrac { Natality }{ Mortality } \times 100$

Answer 1

Hint: It depends on the two factors birth rate and death rate that affect population growth. These factors are also used in measuring the population density.

Complete answer:
The vital index is the ratio between natality or number of births and mortality or the number of deaths in a given time duration. The vital index can be expressed as $\cfrac { Natality }{ Mortality } \times 100$ .

Additional Information: -Population growth is a dynamic factor and it keeps changing from time to time. Several factors affect the population of a region. This dynamic nature can provide us with the idea of whether the population is growing or declining.
-The factors affecting the population are as follows:
Natality: It is a measure of the total number of births within a defined time duration that is added to the initial population.
Mortality: It is a measure of the total number of deaths happening in a given population within a given time duration.
Immigration: It is a measure of the total number of individuals of a particular species joining the population of a different habitat from another place within a given time duration.
Emigration: It is just opposite to immigration, it measures the total number of individuals of a particular species that have left their original habitat to move on to a different habitat, within a given time duration.
-The population density at a time t can be expressed after a time duration of t+1 Nby the following equation: ${ N }_{ (t+1) }={ \quad N }_{ t }+[({ B }+{ I })-({ D }+{ E })]$
Where N is population density, B is natality, D is mortality, I is immigration and E is emigration.
So, the correct answer is,” The vital index means $\cfrac { Natality }{ Mortality } \times 100$.”

Note: It is important to know that these factors determining population growth do not apply to every organism's population. In plants, for example, both are factors immigration and emigration are non-operative because plants show no movement from one location to another location, they remain fixed in a region.