Logistic growth is when the growth rate of a population decreases as the number of its members increases. It occurs when an environment has limited resources. Population expansion decreases as resources become scarce and levels off when the environment?s ability to support the population is reached.
A logistic population graph is characterized by an S-shaped curve with three distinct regions. The population size initially grows slowly when it has only a few members. As the number of members increases, the rate of growth increases exponentially because there are more members to reproduce and ample available resources.
However, the population eventually reaches the maximum number of members that the environment can sustain. At this point, the number of members is large enough to deplete resources, which causes the growth rate to slow and then level off.
The level at which the population size plateaus is known as the carrying capacity of the environment. It represents the maximum population size a particular environment can support and is characterized by little change in population size over time.
Yeast provides a classic example of the S-shaped curve when it is grown in a test tube. Its growth rate levels off as the microscopic fungus depletes the nutrients that are required for its growth.