The human population is more than 5 billion. It is the most abundant species which has a great competition from the insects and fishes. The human beings are adapted to the climate and edaphic factors. Most of the animals have a specific breeding period. But human beings and a few domestic animals have no such specifications. The animals with the specific period of breeding are frog, lion, deer and parrot. The human beings are quite active reproductively. Their population has raised so much in the last few decades. In the year 1991 the growth was little bit slower. But in the year 1981 the growth was fast. The sex ratio also declined from the existing ratio in the year 1981. However, there has been increase in the population density in the present census as compared with the 1981 census. The most thickly populated state in India is the West Bengal. The most thinly populated state in India is the Arunachal Pradesh. The Delhi is the most populated union territory and the Andaman and Nicobar islands are the least populated union territory. The maximum literacy rate is in Kerala and the minimum literacy rate is in Bihar. The highest literacy rate in the union territory is in Chandigarh. The most populous state of India is the Uttar Pradesh. The lowest populous state of India is the Sikkim. The china is the most populous country in the world. India is the second most populous country of the world. The most thickly populated country is Bangladesh. The most thinly populated country is Australia.
The demography is defined as the study of all aspects of the population. It includes the number, age, sex, education and status. It occurs by census. It is done after every 10 years. It usually takes 12 months to complete a census. It indicates the trend of the population and its growth. It takes into account almost every factors linked with the growth of population. It also tells about the number of children receiving education, unemployed, employment and their economic status. The theory of population was given by Malthus. It states that the population grows geometrically and the food grows arithmetically.
