query: What does a population mean?
passage: Population
In biology, a population is the number of all the organisms of the same group or species, which live in a particular geographical area, and have the capability of interbreeding.[1][2] The area of a sexual population is the area where inter-breeding is potentially possible between any pair within the area, and where the probability of interbreeding is greater than the probability of cross-breeding with individuals from other areas.[3]
passage: Population change
Human population change is the difference between the size of the population from the beginning to the end of a certain time period. In other words,population change refers to change in the number of people during a specific time period. As a whole,the world population has not been stable; it has increased manifold. Due to this constant changing population, the subject of demographics, the statistics of how many people there are in a given population, was created. Demography can also be defined as the study of populations, and the factors that cause the most amount of population growth or decline. The main measurements of demography include: birth rates, death rates, sex ratios, life expectancy, and migration rates. All of these measures are found by a series of surveys and censuses conducted over a time period in order to compare how the population is changing. Other ways to measure population demographics include the use of historical maps, aerial photographs, and census statistics. One of the reasons why demographers use statistics about population change is because of the social and demographic transformations that the world experiences; significant challenges for the government and businesses will take effect depending on the degree of the population change.