Introduction
The Competitive Exclusion Principle was first proposed by G.F Gause. According to the principle he stated, those species which compete for the same resources cannot coexist. This principle is also known as Gause’s law. By this law, it is stated that one population will drive off the other one. The one remaining in the system definitely has strong adapting capacity. Let's suppose that, if a forest's maximum population is carnivores, then definitely in that area there will be a shortage of food. This will cause scarcity of food among animals which causes competition among the animals due to competition of best survival. The one who has strong power will definitely defeat the weaker section and by the passage of time, the weaker section will get eliminated.
One more example of competitive exclusion is, how red squirrels replaced the grey squirrels in Britain? Suddenly the number of squirrels decreased in Britain because of the disappearance of hazelnuts, which led to competitive exclusion. Whereas gray squirrels adapted to the situation and replaced the red squirrels eventually.
History:
The competitive exclusion principle was initially given by Georgii Gause, but basically, he never formulated this principle. This principle was already there in Darwin’s theory of natural selection. This principle revolves between a priori and experimental truth.
Prediction:
The competitive exclusion principle is also predicted by mathematical and theoretical models like Lotka-Volterra medals of competition. But because of its weak reasons, competition exclusion is hardly observed in natural ecosystems, and many biological communities appear to violate Gause’s law. One of the best-known examples is the so-called “paradox” of the plankton. All plankton species survive on a very limited number of resources, mainly on solar energy, only a very small number of plankton species should be able to coexist on these resources.
Types of Competition In Competitive Exclusion:
There are mainly two types of competitions in the competitive exclusion principle:
1. Interspecific Competition: In this, competition takes place between organisms of different species.
2. Intraspecific Competition: In this, competition takes place between organisms of the same species.
Sub-Types of Competitions:
1. Interference: Where there is a direct flight between organisms for resources, it is called interference. For example: when animals protect their food from other animals, for best survival.
2. Exploitation: It is a condition when an organism uses all resources, leading to depletion of resources for other animals. Such a condition is known as exploitation. In this condition, there is a direct fight for resources. It is a natural phenomenon and leads to the evolution of organisms.
3. 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 has its own capacity to fit in its ecological community and have a tendency to tolerate various environmental factors to a certain extent. Example: Species of fish is classified on the basis of specific salinity range, pH level and also the type of food they consume.
In case, if two organisms have the same niche, then it is very difficult to survive in the same environment due to the presence of competition between them.
4. Resource Partitioning: In case if one or both the species belong to the same niche, then they undergo evolution to use their resource in different ways or they develop best feeding habits for best survival and by this method competition exclusion can be avoided. As such, the evolution process leads to non-overlapping of resources resulting in different niches. By this process, it becomes easy to exist together.
For example, Anole lizards are found in large numbers in the Island of Puerto Rico. These lizards evolved over time due to the natural selection process and they got further differentiated into 11 more new species that use different kinds of resources and also live in different habitats. This is the example of resource partitioning.
Important Questions
How many types of competitions are present according to the Competitive Exclusion Principle?
Ans: There are broadly two types of competitions known - Interspecific competition and Intraspecific competition.
Which of the following best describes an Ecological Niche?
A cramped, small habitat
A hole in the food chain
An organism's role in its ecosystem
The losing species of competitive exclusion
Ans: An ecological niche basically describes the way an organism survives, feeds itself, and builds its shelter in its environment. It means ecological niche talks about the role the organism plays and how it responds to its environment. Hence, the correct option is (c).
Key Features
Competitive Exclusion Principle states that species competing for the same resources or food do not exist together and one turns up driving off the another one.
The principle is also known as the ‘Gause’s law’ as it was first proposed by G.F Gause.
There are broadly two types of competitions - Interspecific competition and Intraspecific competition.
FAQs on Competitive Exclusion Principle
1. What is the Competitive Exclusion Principle, as stated by Gause?
The Competitive Exclusion Principle, often called Gause's Law, states that two species competing for the exact same limited resources cannot coexist at constant population values. When one species has even a slight advantage over another, the one with the advantage will dominate in the long run. The other species will either be driven to extinction or undergo an evolutionary or behavioural shift toward a different ecological niche.
2. Can you provide a classic example of the Competitive Exclusion Principle from an experiment?
A classic example is G.F. Gause's experiment with two species of Paramecium: Paramecium aurelia and Paramecium caudatum. When grown in separate cultures with a constant food supply, both species thrived. However, when they were placed in the same culture, P. aurelia consistently outcompeted P. caudatum for food, leading to the eventual elimination of the P. caudatum population. This demonstrated that the superior competitor can exclude the other species when they share the same niche.
3. What is the main difference between interspecific and intraspecific competition?
The main difference lies in the organisms involved:
Interspecific competition occurs between individuals of different species that require the same limited resources, such as lions and hyenas competing for the same prey.
Intraspecific competition occurs between individuals of the same species, such as two male deer competing for mates or seedlings of the same plant species competing for light and soil nutrients.
4. How do species in nature often avoid competitive exclusion?
Species avoid competitive exclusion primarily through two mechanisms:
Resource Partitioning: Species evolve to use the same resource in different ways, at different times, or in different places. For example, several species of warblers can coexist in the same spruce tree by feeding on insects in different parts of the tree (e.g., top branches, middle branches, or trunk).
Character Displacement: The characteristics of competing species diverge more in areas where they coexist (sympatry) than in areas where they do not (allopatry). For instance, two bird species might evolve different beak sizes in a shared habitat to specialise on different-sized seeds, thus reducing competition.
5. Why is the Competitive Exclusion Principle a key concept in ecology?
This principle is fundamental to understanding the structure and diversity of ecological communities. It explains why certain species are found in particular habitats and not others. It also highlights the powerful role of competition as a driving force of evolution, pushing species to adapt and occupy distinct niches. This process, known as niche differentiation, is a major reason for the rich biodiversity we see in ecosystems.
6. Does the Competitive Exclusion Principle always apply in natural ecosystems?
No, the principle describes an outcome under stable, idealised conditions that are rare in nature. In the real world, several factors can prevent the exclusion of a weaker competitor, allowing for coexistence. These factors include environmental fluctuations (which may favour different species at different times), the presence of predators that may keep the superior competitor's population in check, and the availability of multiple resources that prevent complete niche overlap.
7. What are the main types of competitive interactions explained in ecology?
There are two primary types of competitive interactions:
Interference Competition: This is a direct interaction where one organism actively prevents another from accessing a resource. This can involve fighting, territorial behaviour, or producing chemical toxins to inhibit the growth of a competitor (allelopathy in plants).
Exploitation Competition: This is an indirect interaction where species compete by consuming the same limited resources. There is no direct confrontation; the presence of one species simply reduces the amount of resource available to the other.
8. How is the concept of an 'ecological niche' related to the Competitive Exclusion Principle?
The concept of an ecological niche is central to the principle. A niche represents the total range of environmental conditions and resources an organism requires to survive and reproduce. The Competitive Exclusion Principle is essentially a restatement of this idea: no two species can occupy the exact same niche in the same habitat at the same time. The greater the niche overlap between two species, the more intense the competition will be, ultimately leading to the exclusion of one or the evolution of niche differentiation.
