What is competition? State Gause's competitive exclusion principle and explain how species can coexist despite competition.

1. 1 · Define in one line. Competition is a (−, −) interaction in which the fitness (r) of one species is significantly lower in the presence of another.
2. 2 · Correct two common ideas.
   • Unrelated species compete too: flamingoes and fishes for zooplankton.
   • Resources need not be limiting: interference competition.
3. 3 · Give evidence from nature.
   • The Abingdon tortoise died out after goats reached the Galapagos.
   • Competitive release: Balanus excludes Chthamalus (Connell).
4. 4 · State Gause's principle. Closely related species competing for the same resources cannot coexist indefinitely; the inferior one is eliminated, if resources are limiting.
5. 5 · Explain coexistence. Resource partitioning: different feeding times or foraging patterns; MacArthur's five warbler species on one tree.
6. 6 · Link to real life. Weeds compete with wheat and rice for water and minerals, so farmers remove them.
7. 7 · Close in one line. So competition shapes where species live, and partitioning lets many species share one habitat.

Scoring tip: Name the scientist with each example: Gause (exclusion), Connell (barnacles), MacArthur (warblers).