Population - Limiting factors and growth curves

Limiting factors

Populations can change over time due to many factors or variables. These can be classified as:

• Density dependent factors
• Density independent factors

Density dependent factors are biotic

• They act as negative feedback
• Regulate and stabilize populations
• Internal factors act within the species (such as limited food supply)
• External factors act between different species (such as predation)

Density independent factors are abiotic

• They represent no feedback system
• Acts over all the ecosystem no matter the species that are present or the density
• Weather, climate, floods, storms.

Population curves

S-curve

• Starts with exponential growth
• Growth rate stabilizes
• Stabilize at carrying capacity (K)
• The area between the exponential growth curve and the S curve is called environmental resistance.
• lag / exponential / deceleration / stationary

J-curve

• Shows a boom and bust pattern
• Grows exponentially and then crashes
• Collapses are called diebacks
• Exceeds K (overshoot)
• Typical of microbes and invertebrates.