The world population is derived from the Latin word popular which means people. It is often used to refer human such as the human population in a city. But in the biological sense, a population is an assemblage of organisms (plants or animals) which belong to a single species or to several closely related species occupying a particular area, as for example, bullfrogs in a pond, grasshoppers in a field or pone trees in a forest. According to WYNNE EDWARDS (1965), a population is a self regulating system.
CLARKE (1954) has distinguished two types of population : (I) Monospecific with individuals of the same specific and (2) mixed or polyspecific with individuals of several species.
Characteristics Population – According to THOMAS PARK, a population has several characteristics or attributes which are a function of the whole group and not of the individual. These are —
1. Population density 2. Depression
3. Birth-rate 4. Dispersal
5. Death-rate 6. Biotic potential
7. Age-distribution 8. Population equilibrium
9. Growth form 10. Population fluctuations.
The rapid increase in population over the last four decades is referred to as population exploitation. This has been caused by:
(a) High birth rate
(b) Sharp decline in death rate.
This in turn has been caused by following factors
(i) Universal and early marriage in India.
(ii) Our ability to control famines and epidemics.
(iii) Improved sanitation and medical health facilities.
(iv) Ignorance about and lack of willingness to adopt birth control measures. .
What do you understand by Population Density?
Population density can be defined as the number of individuals per unit area or per unit volume. The units of population density differ in different cases, as for example, the number of squirrels per square mile, the number of earthworms or trees per acre and the number of diatioms per litre of water. When the individual size in a population Is highly variable, some type of biomass or live weight measured. is used as an unit of density. Thus the unit measurement varies for different types of populations.
There are two ways of expressing the population density, the crude density and the ecological density. The crude density is the total number of individual or biomass per unit of total area or total volume. Ecological density is the number of individuals or the biomass per unit of that area or volume which is actually inhabited by those individuals.