LIMITING FACTORS

F3.3 – LIMITING FACTORS

• a factor that causes popn growth to decrease
• two basic types:
1. density-independent factors
2. density-dependent factors
1. Density-independent factors
• an abiotic event that affects all popn’s in the same way, regardless of popn density
• e.g. fires, earthquakes, storms, temperature extremes…

2. Density-dependent Factors
• a biotic interaction that varies in its effect on popn size, depending on the density of the popn involved
• have greater impact on denser popn’s
• examples of density-dependent factors:
A. Competition
B. Predator-prey interactions
C. Communicable diseases

A. Competition
• an interaction in which individuals vie for access to the same resource(s) • intraspecific – competition w/in the same species o e.g. individual plants compete for the same space to grow
• interspecific – competition b/w different species o e.g. lions and hyenas compete for the same food sources
• inter- usually one species will out-compete the other, but can also result in resource partitioning, driving evolution o e.g. warblers

Each species of warbler can forage in the same tree because each feeds on insects that are found in different parts of the tree.
Each warbler occupies a slightly different
‘niche’.

B. Predator-Prey Interactions
• an interaction in which one organism consumes all or part of another • popn growth follows cyclic patterns:

o rise and fall of predators follows that of prey o prey population usually reaches max before predator o prey population should always exceed predator