Community Ecology

Rucete ✏ Biology In a Nutshell

1. Competitive Exclusion Principle (Gause’s Principle)

• Two species cannot coexist if they compete for the exact same niche
• One will outcompete the other and cause local extinction
• Leads to resource partitioning

2. Resource Partitioning

• When species divide up resources to reduce competition
• Example: birds feeding at different heights in a tree

3. Character Displacement

• Species that compete evolve differences in traits to minimize overlap
• Common in species with overlapping ranges

4. Niche Concepts

• Fundamental Niche: the full range a species could potentially occupy
• Realized Niche: the actual range it occupies due to competition

5. Types of Predation

a) True Predator

• Kills and eats another animal

b) Parasite

• Lives on or in a host and feeds off it, usually without killing it

c) Parasitoid

• Lays eggs inside a host; larvae feed on the host, eventually killing it

d) Herbivore

• Feeds on plants
  • Granivores eat seeds
  • Grazers eat grasses
  • Browsers eat leaves and shrubs

6. Symbiosis

a) Mutualism

• Both species benefit

b) Commensalism

• One species benefits, the other is not affected

c) Parasitism

• One species benefits at the expense of the other