A population has varied characteristics than an individual. Some of which are:
A) A population has birth rate (natality) and death rate (mortality) whereas an individual has birth and death.
1. An individual is either male or female. A population has sex ratio which the number of females per 1000 males.
2. A population has different age groups whereas an individual is of specific age.
B) Population Density: It is the number of individuals per unit area. This density changes with time and space. Example: There are 500 insects per 100 km square. It is calculated by quadrant method, direct or indirect observations.
C) Population Growth: It is the growth rate seen in a population over time. It is represented by population growth curve where number of individuals are plotted on the y-axis and the time is plotted on the x-axis. A curve is obtained showing the growth or decline in a population. It is of two kinds S shaped sigmoid curve and J shaped curve. Example:
D) Natality: It is the rate of reproduction or birth rate per unit time. Increased natality shows increasing population. It can be calculated by the following method:
NUMBER OF BIRTHS PER UNIT TIME/AVERAGE POPULATION X 1000
E) Mortality: It is the rate of deaths per unit time. Increased mortality shows a decline in population. It can be calculated by the following method:
Number of Deaths/Time
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