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The logistic population growth curve is usually observed in yeast cells cultivated in laboratory conditions and includes five phases, namely:
тАв The lag phase тАУ the population of yeast cell is small initially as resources are limited in the habitat
тАв Exponential phase тАУ in this stage, the population of the yeast cell suddenly rises as a result of rapid growth leading to an exponential population growth due to availability of enough food resources, consistent favorable environmental conditions without any interspecific competition. This results in the curve rising upwards steeply.
тАв Positive acceleration phase тАУ at the start of this phase, the cell growth is limited. The yeast cell adjusts to the new environment and grows its population
тАв Negative acceleration phase тАУ the environmental resistance increases and the growth rate of the population declines as a result of an increased competition between the yeast cells for shelter and food.
тАв Stationary phase тАУ The population is stable in this phase. The count of cells generated in a population is equivalent to the number of cells that die out. Additionally, the speciesтАЩ population is said to have touched natureтАЩs carrying-capacity in its habitat. S-shaped growth curve is also referred to as the Verhulst- pearl logistic curve.
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