Question

Gause's Competitive Exclusion Principle states that:

• A. Two species always coexist
• B. Species compete only indirectly
• C. Two species with identical niche cannot coexist indefinitely
• D. Competition increases biodiversity

Hint:

Key phrase: "Complete competitors cannot coexist."
If you see the word "Niche" and "Exclusion" in a question about Gause, they are directly related.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
G.F. Gause formulated this principle based on his experiments with Paramecium.
A "niche" is the specific functional role and resource requirements of a species.

Step 2: Detailed Explanation:
The principle states that two species competing for the exact same limiting resources (identical niche) cannot live together in the same place for a long time.
In such a scenario, one species will eventually prove to be slightly more efficient in using those resources.
The superior competitor will increase its population while the inferior one declines.
Eventually, the inferior competitor will be "excluded" or eliminated from that habitat.
Coexistence is only possible if the species evolve to use different resources (Resource Partitioning).

Step 3: Final Answer:
Gause's principle concludes that intense competition in identical niches leads to the local extinction of the weaker species.

Answer 2

Each option can be checked word by word against what the Competitive Exclusion Principle actually claims about species sharing a niche.

1. Two species always coexist: This directly contradicts the principle, which describes a specific condition (identical niches) under which coexistence fails rather than a rule that guarantees coexistence in every case.
2. Species compete only indirectly: The principle is built on direct exploitation of the same limiting resource, such as both species drawing down the same food supply, so restricting it to indirect competition misstates the mechanism entirely.
3. Two species with identical niche cannot coexist indefinitely: This matches the principle precisely. When two species require the exact same resources and space, even a very small difference in efficiency at using those resources means one will out-reproduce the other over time, and the less efficient species is eventually displaced or driven locally extinct.
4. Competition increases biodiversity: The principle describes the opposite outcome, since complete niche overlap results in the loss of one competitor from that habitat rather than an increase in the number of species present. Diversity is instead preserved when competing species partition resources into different niches, which is a separate idea from what this principle states.

Only the statement about identical niches leading to exclusion reflects what Gause actually demonstrated.

Hence, the correct answer is Two species with identical niche cannot coexist indefinitely.