Competitive Exclusion Principle

The principle of competitive exclusion was proposed by G.F. Gause which states that two species competing for the same resources cannot coexist. This law is also known as Gause’s law.

One population will drive off the other one. If any of the members of the depleted population remains, that would be because they have adapted themselves according to the different niche.

For eg., if a forest has maximum carnivorous animals, that area will always have food scarcity. Due to the scarcity of food, there will competition among the animals due to survival issues. The strong ones will win over the weaker group and will solely flourish.

Another example of competitive exclusion is, the red squirrels replacing the grey squirrels in Britain. The number of red squirrels decreased because of the disappearance of hazelnuts, competitive exclusion, and diseases. Gray squirrels easily adapted to the environment and replaced the red squirrels gradually.

There are two kinds of competitions according to the competitive exclusion principle:

  • Interspecific Competition

  • Intraspecific Competition

Also read: Extinction

Types Of Competitions

  1. Interspecific: The competition that takes place between the organisms of different species is known as interspecific competition.

  2. Intraspecific: The competition that takes place between the organisms of the same species is known as intraspecific competition.

Sub-types Of Competitions


When the organisms directly fight with each other for resources, it is known as interference. For eg., animals protect their food from other animals.


When the organisms consume all the resources leaving nothing for the other organisms, it is known as exploitation. In this case, they indirectly fight for resources. Competitive exclusion is a natural phenomenon which is responsible for the evolution of organisms.

Also read: Endangered Species

Ecological Niche

The niche is the way of life of a species marked by the set of conditions, resources and interactions it requires. Every species fits into its ecological community and can tolerate various environmental factors to a certain extent. For eg., a fish species niche is classified on the basis of a specific salinity range, pH, temperature and type of food it consumes.

If two organisms have the same niche, it is very difficult for them to survive in the same environment due to the competition.

Resource Partitioning

If one or both the species belonging to the same niche evolve to use different resources or develop different feeding habits, competitive exclusion can be avoided. Due to this evolution, the species start using non-overlapping resources resulting in different niches. This is termed a Resource Partitioning. This helps the species to exist together.

For eg., The island of Puerto Rico is the abode for a large number of anole lizards. They evolved over time due to natural selection and differentiated into 11 species that use different resources and live in different habitats. This is one fine example of Resource Partitioning.

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Extended Reading:

Practise This Question

A statement of assertion is followed by a statement of reason.

Assertion: In a regular medical examination of a small population, a 35 years old lady was found to have higher levels of oestrogens, progesterone in her blood.
Reason: The lady is 12 weeks pregnant.

Mark the correct choice as: