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Not all individuals are able to survive and reproduce due to genetic variations in them.

A discrete assemblage of entities with identifiable characteristics such as people, animals with the objective of analysis and data collection is called a population. It consists of a similar group of species who dwell in a particular geographical location with the capacity to interbreed. To interbreed, individuals in a population must be able to mate with other individuals in order to produce fertile offspring.

Not all individuals are able to survive and reproduce due to genetic variations in them.

A local population can be restricted to a smaller area or can occupy a larger area, making up for the entire species.

A metapopulation is when individuals in local populations scatter between other local populations.

Most of the populations are not stable due to various physical factors prevailing in the environment which act as limiting factors against exponential growth of the population.

A graph that displays the age-sex distribution of a country’s  human population  at a given frame of time is referred to as a population pyramid. It shows the variation in the population of the male and females with age that is otherwise (bar graphs) not feasible. It results in a pyramidal structure where the population is on the x-axis and age is on the y-axis.

There are three types of population pyramids:

It is triangular in shape wherein each age group displays a bar shorter than the one preceding it, symbolising that more people die as we progress through the pyramid. A large base indicates a high birth rate. The tapering top of the graph indicates the lesser life expectancy of a region.

With a slight reduction in the younger group of age, it is the opposite of expansive pyramid. Life expectancy is higher and living conditions are better indicating a high number of older citizens. Despite this, a decrease in population is seen due to fewer birth rates compared to the death rate.

It is rectangular in shape indicating an equal distribution of people across all age groups. A slight tapering at the top denotes more death occurring among the older people, which is natural. A stable birth rate indicates the use of birth control measures. Life expectancy in such regions is high due to better living conditions, availability of medical services etc.