**Understanding:**

• The exponential growth pattern occurs in an ideal, unlimited environment

• Population growth slows as the population reaches the carrying capacity of the environment

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 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 a geometric 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
- This maximal growth rate for a given population is known as its
**biotic potential** - Exponential growth can be seen in populations that are very small or in regions that are newly colonised by a species

**Logistic Growth**

- 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
**κ**) - Logistic growth will eventually be seen in any stable population occupying a fixed geographic space

**Types of Population Growth**

**Limiting Factors**

Limiting factors are environmental conditions that control the rate at which a process (e.g. population growth) can occur

- Population growth can be determined by density-dependent or density-independent factors

Density *dependent* environmental factors are influenced by the relative size of a population

- These factors include predator numbers, availability of food and other resources and the spread of pathogenic diseases

Density *independent* environmental factors are **not** influenced by the relative size of a population

- These factors include weather and climate conditions, as well as the occurrence of natural disasters (e.g. earthquakes)

**Examples of Population Factors**