What is the difference between birth rate and death rate?

Hint:Birth rate or natality and death rate or mortality are the two characteristics of population. They were used for measuring population density along with immigration and emigration.

Complete answer:
Before discussing the differences between birth rate and death rate, we should discuss definitions of population, birth rate and death rate. Population is a group of interbreeding individuals of same or closely related species, living together in a geographical area with mutual interaction and genetic exchange.

Natality or birth rate is the rate of production of new individuals in a population during a unit time by birth, hatching or germination. It is an important contributing factor for population growth. Mortality or death rate is the number of deaths of the individuals of a population per unit time. Both death rate and birth rate are species specific and death rate is sex specific too. Natality can be positive or zero but never negative. Under ideal conditions the mortality rate will be the lowest. The highest possible natality, that can be visualized under ideal conditions is known as potential natality. Whereas, the lowest possible death rate that can be expected under most ideal conditions is called potential mortality. Both potential mortality and natality occurs very seldom.

The actual birth rate under normal natural conditions is known as realized natality, also the actual death rate under normal natural conditions is called realized mortality. They both vary with populations and environmental conditions.
In general, realized natality is always less than potential natality and realized mortality is higher than potential mortality.
Females have an edge over males in having lower mortality and higher mean duration of life. In the case of human beings, there is an inherent biological difference between males and females which favors lower mortality in females.
Under normal natural conditions, natality and mortality will be delicately balanced in order to maintain the steady state density of population. But, when natality supersedes mortality, population size and density increase abnormally. Also, when mortality overrides natality, population size and density decrease very much.

Additional information:
Population is said to be monospecific, when its members belong to one and the same species or poly-specific or mixed, when the members belong to closely related species.
Natality increases the number of individuals there by population density, whereas mortality decreases population density.
The ratio between natality and mortality is known as the vital index.


Note: The size of a population for any species is not a static parameter. It keeps changing in time, depending on various factors such as food availability, predation pressure and adverse weather. Under normal ideal conditions, births and deaths are the most important factors influencing population density, whereas immigration and emigration assume importance only under special conditions.