Demography is the study of human populations – their size, composition and distribution across space – and the process through which populations change. Births, deaths and migration are the 'big three' of demography, jointly producing population stability or change.
Demography means study of population.It is derived from greek work 'Demos' which means people and 'graphein' which means study.The woed was first coined by Achille Guillard in 1855.But John Graunt is known as the father of demogrphy because he described population in demographic way.
Demography is the statical study of birth,death and migration.
They are able to respond to the presence of invading organisms because they recognize the<u> antigen </u>on the surface of organisms. There are specific receptors on the surface of immune system cells.
