In a laboratory, if 50 Drosophila out of a population of 250 die in a week then the death rate of Drosophila is_________ individual per Drosophila per week.

0.2

The correct answer is Option (1) -0.2

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.

 If 50 individuals in a laboratory population of 250 fruitflies die in a week then the death rate of Drosophila is 50/250 = 0.2 individuals per fruitfly per week.

Death rate = (Number of deaths) / (Total population)

In this case:

Death rate = 50 deaths / 250 Drosophila

Death rate = 0.2 deaths per Drosophila per week