Which of the following examples demonstrates competitive exclusion in nature?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → The dominance of Balanus barnacles over Chathamalus barnacles in intertidal areas
Gause’s Competitive Exclusion Principle says that two closely related species competing for the same resources cannot live together for ever; the weaker competitor is finally removed. Competitive exclusion is this removal of one species by a stronger competitor.
Option (1) Barnacles growing on the back of a whale — Incorrect. An organism gaining a place to live while the other is neither harmed nor helped is commensalism. The whale is not affected by the barnacles, so there is no competition.
Option (2) Interaction between sea anemone that has stinging tentacles and the clown fish — Incorrect. The clown fish gets protection among the stinging tentacles, and the anemone does not seem to gain anything. This is also commensalism, not competition.
Option (3) The dominance of Balanus barnacles over Chathamalus barnacles in intertidal areas — Correct. In Connell’s field experiments on the rocky sea coasts of Scotland, the larger and stronger barnacle Balanus took over the intertidal zone and excluded the smaller barnacle Chathamalus from it. This is competitive exclusion seen in nature.
Option (4) The coexistence of closely related warbler species through resource partitioning — Incorrect. Here the warblers avoid competition and co-exist by feeding in different ways. This is resource partitioning, the opposite of exclusion.
NCERT Extract:
Population Interactions – “… Connell’s elegant field experiments showed that on the rocky sea coasts of Scotland, the larger and competitively superior barnacle Balanus dominates the intertidal area, and excludes the smaller barnacle Chathamalus from that zone. In general, herbivores and plants appear to be more adversely affected by competition than carnivores. Gause’s ‘Competitive Exclusion Principle’ states that two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually.”