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| Population Growth |
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| The growth of population is measured as increase in its size over a period of time and populations show characteristic patterns of growth with time. These patterns are known as population growth forms. |
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| There are two basic population growth forms. |
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| i) J - shaped population growth form. |
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| ii) S - shaped population growth form. |
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| In J-shaped population growth form, the population grows exponentially and after attaining the peak value, the population will crash abruptly. |
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| In S - shaped or sigmoid growth the population show an initial gradual increase in population size, followed by an exponential increase and then a gradual decline to near constant level. |
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| Sigmoid growth curve is formed of five phases. |
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| a) Lag phase |
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| b) Positive acceleration phase |
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| c) Logarithmic or exponential phase |
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| d) Negative acceleration phase |
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| e) Stationary phase. |
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| a) Lag phase - Period where individuals adapt to the new environment. |
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| b) Positive acceleration phase - Period of slow increase in the population |
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| c) Logarithmic or exponential phase - Period of rapid rise in population due to availability of food and requirements in plenty and no competition. |
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| d) Negative acceleration phase - Period in which these is a slow rise in population as the environmental resistance increases. |
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| e) Stationary phase - Finally, growth rate becomes stable because mortality and natality rates become equal. |
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