 Dear students, in this module, we are going to talk about the population and population-related problems. As you know, the population where refers to the group or general, in general and also the size of population or the number of individuals it contains, it means that it possesses the total collection of human beings or the collection of individuals. So, if we talk about the population or of a particular geographic area, it means the number of people in a city, town, region, country or around the globe. So, usually it is determined by the process which is called census and normally these census statistics are collected on a decade basis for each decade. We have to produce census by physically counting the number of inhabitants in any specific geographic area. So, if we are more concerned about the population issues, we have to understand the characteristics of population. So, by characteristics number one, we mean that we need to understand the population distribution for which we have the indicators like dispersion. Dispersion means that the special arrangement of organisms within an area, that how dispersed they are in a specific geographic area. And then being random or haphazard means that how haphazardly located those individuals are. It might be with the proper pattern or without any standards. For the uniformity, we need to understand that individuals are evenly spaced due to the territorial territoriality or the territorial boundaries. Columpt means that population is arranged according to the availability of resources. For example, the people are more densely located in the areas where there are more resources and would be scarcely located where there are less resources. Then we have to understand the sex ratio, which means that the proportion of males to the number of females. So, in the monogamous species, like the 50-50 of sex ratio, maximizes the population growth. For example, in the human beings as well, it is also considered a perfectly harmonious or balanced population where these 50-50 ratios are achieved. And then we have another indicator which is called the age structure, which is the relative number of organisms of each age within the population. Factors which are contributing to population change are fertility, mortality, immigration and emigration. So, it means that these are the contributing factors which can affect the size of the population. Fertility means the natural capability of an individual to produce the number of offspring. It is usually calculated for the female that how, for example, what are the fertility ages? Usually, the fertile ages are calculated between 15-40 years and then we have the mortality as an indicator. It also means the number of deaths within a specific population. So, if we want to calculate the total population, we have to take into account the fertility rate as well as the mortality rate. Immigration is also an important indicator, which means the arrival of individuals from outside the population and emigration is vice-versa, which means that the departure of individuals from the population. So, combining all these indicators would help us determine the total population size of any country.