19: Competition

Reading: Chapter 15

Competition: a negative interaction between two species that depend on the same limiting resource
Competition occurs, but organisms should avoid it to save resources

Intraspecific competition: Competition among individuals of the same species
Interspecific competition among individuals of different species
Resource: Anything an organism consumes or uses that causes an increase in the growth rate of a population when it becomes more available
- Examples: Holes that allow a prey to hide from a predator, Soil nitrogen, Nesting sites in a dead tree, Space
Liebig’s law of the minimum
- Law stating that a population increases until the supply of the most limiting resource prevents it from increasing further.
  - However, there are interactions among resources. Nutrients x light
Competitive exclusion principle
- The principle that two species cannot coexist indefinitely when they are both limited by the same resource.

Abitoic conditions
Predation and Herbivory
- The presence of predators affect competition interactions
  - Predators can keep in check a dominant competitor
Exploitation, interference, or apparent competition
- Exploitative competition — Competition in which individuals consume and drive down the abundance of a resource to the point that other individuals cannot persist.
- Interference competition — When competitors do not immediately consume resources but defend them.
- Allelopathy — A type of interference that occurs when organisms use chemicals to harm their competitors.
Apparent competition: when two pseices have a negative effect on each other through an enemy including a predator, parasite, or herbivore