Gause's competitive exclusion principle: two species competing for one resource cannot coexist. Lotka-Volterra competition: ṅ₁ = r₁n₁(1−n₁/K₁−α₁₂n₂/K₁), ṅ₂ = r₂n₂(1−n₂/K₂−α₂₁n₁/K₂). Four outcomes determined by nullcline intersections. Explore the phase plane.
Outcome: — | Coexistence iff α₁₂ < K₁/K₂ AND α₂₁ < K₂/K₁