Population Growth Graphs
Two types of population growth patterns may occur depending on specific environmental conditions:
- An exponential growth pattern (J curve) occurs in an ideal, unlimited environment
- A logistic growth pattern (S curve) occurs when environmental pressures slow the rate of growth
- Exponential population growth will occur in an ideal environment where resources are unlimited.
- In such an environment, there will be no competition to place limits on the rate of growth.
- Initially population growth will be slow as there is a shortage of reproducing individuals that may be widely dispersed.
- As population numbers increase the rate of growth similarly increases, resulting in an exponential (J-shaped) curve.
- Exponential growth can be seen in populations that are very small or in regions that are newly colonised by a species.
- Exponential growth does not happen in natural populations for very long because the resources get used up. Population growth slows down when food and space become more difficult to find.
- Logistic population growth will occur when population numbers begin to approach a finite carrying capacity.
- The carrying capacity is the maximum number of a species that can be sustainably supported by the environment.
- As a population approaches the carrying capacity, environmental resistance occurs, slowing the rate of growth.
- This results in a sigmoidal (S-shaped) growth curve that plateaus at the carrying capacity (denoted by K).
- Logistic growth will eventually be seen in any stable population occupying a fixed geographic space.