CHAPTER 4.POPULATION AND DEMOGRAPHY
 
WHAT IS POPULATION?
Population, in human biology, is the whole number of inhabitants occupying an area ( such as a country or the world) and continually being by increases (births and immigrations) and losses (deaths and emigrations).
As with any biological population, the size of a human populations is limited by the supply of food, the effect of diseases, and other environmental factors. Human populations are further affected by social customs governing reproduction and by the technological development, especially in medicine and public health that reduced mortality and extended the life span.
 
POPULATION
FERTILITY-demographers distinguish between fecundity, the underlying biological potential for reproduction, and fertility, the actual level of achieved reproduction. The difference between biological potential and realized fertility is determined by several intervening factors, including the following.
1.
Most women do not begin reproducing immediately upon the onset of puberty, which itself does not occur at a fixed age;
2.
Some women with the potential to reproduce never do so;
3.
Some women become widowed and do not remarry;
4.
Various elements of social behavior restrain fertility; and
5.
Many human couples choose consciously to restrict their fertility by means of sexual abstinence, contraception, abortion, or sterilization.
 
POPULATION
POPULATION GROWTH-in biology or human geography, population growth is the increase in the number of individuals in a population. Global human population growth amounts to around 83 million annually, or 1.1% per year. The global population has growth from 1 billion in 1800 to 7.6 billion in 2017. It is expected to keep growing, and estimates have put the total population at 8.6 billion by mid-2030, 9.8 billion by mid-2050 and 11.2 billion by 2100. Many nations with rapid population growth have low standard s in living, whereas many nations with low rates rapid population growth have high standards of living
Population began growing rapidly in the Western world early in the industrial revolution of the late 18
th
century. The reason for the “Modern Rise of Population” were particularly investigated by the British health
scientist Thomas Mckeown(1912-1988). In his publication, Mckeownchallenged four theories abut the population growth.
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