Competition in Science: Definition, Types, and How to Apply the Concept

What Does Competition Mean in Science?

In scientific terms-especially in ecology and evolutionary biology- competition is an interaction where organisms or species share a limited resource, reducing the survival, growth, or reproduction (fitness) of the parties involved. Put simply, when a resource like food, water, light, nutrients, or territory is limited, using it by one individual reduces the amount available to others, decreasing fitness for both competitors [1] [2] [3] .

This interaction operates within a species (
intraspecific
) and between species (
interspecific
) and is a core driver of population dynamics, community structure, and natural selection [1] [2] .

Core Definition and Why It Matters

Definition : Competition is an interaction driven by a shared requirement for a
limiting resource
that diminishes survivorship, growth, or reproduction of the individuals involved [3] [1] . This makes competition a
âˆ’/âˆ’
interaction: both parties incur a cost because each reduces the other’s access to the scarce resource [2] [1] .

Why it matters : Competition shapes who persists and who declines in ecological communities, influences species diversity, and channels natural selection toward traits that reduce direct overlap in resource use or improve efficiency, thereby structuring niches and promoting coexistence mechanisms [1] [2] [4] .

Types and Mechanisms of Competition

Intraspecific vs. Interspecific : Intraspecific competition occurs among members of the same species (e.g., seedlings of one tree species competing for light), while interspecific competition occurs between different species (e.g., grasses and forbs vying for soil nitrogen). Both forms reduce fitness by limiting access to the same scarce resource [1] [2] .

Mechanisms (from most direct to less direct):

Interference : Direct interactions that prevent others from accessing resources (e.g., territorial defense or chemical inhibition) [1] [3] .
Exploitation : Indirectly reducing resource availability by consuming or depleting it faster or more efficiently (e.g., fast nutrient uptake) [1] [3] .
Apparent competition : Not true resource sharing; two species share a predator such that an increase in one boosts predator numbers, harming the other, creating an appearance of competition [1] [2] .

Subtypes of interference include pre-emptive use of space, overgrowth (e.g., shading), chemical inhibition (allelopathy), territorial defense, and encounter competition-each altering access to the limiting resource in specific ways [3] .

How Competition Shapes Evolution and Communities

Natural selection and niche dynamics : By penalizing overlap in resource use, competition favors traits that reduce niche overlap (e.g., different rooting depths, feeding times, or beak sizes), a process often framed as niche partitioning. Over time, this can enable coexistence by minimizing direct competition and facilitating stable community assembly [1] [2] [4] .

Competitive exclusion principle : When two species compete for the exact same limiting resource and occupy the same niche, one will typically outcompete the other-unless they partition resources or environmental variability permits coexistence. Although the principle is foundational, strict exclusion is rarely observed in complex natural ecosystems due to spatial and temporal heterogeneity and adaptive responses [2] [1] .

From individuals to ecosystems : While competition imposes costs on individuals, at the ecosystem level it can contribute to biodiversity by promoting niche differentiation and limiting redundancy, potentially stabilizing communities against certain disturbances [4] .

Real-World Examples

Plants competing for light : In dense forests, taller species can overtop shorter ones, reducing their light and growth-a classic overgrowth mechanism. Shade-tolerant species persist through physiological adaptations, while shade-intolerant species exploit gaps, illustrating coexistence strategies under competition [1] .

Space as a limiting resource in tide pools : Sea anemones and other sessile organisms compete intensively for small patches of rock, where pre-emptive occupation and interference (including aggressive interactions) determine survival and reproduction [1] .

Allelopathy and chemical interference : Some plants release chemicals that inhibit competitors’ germination or growth, reallocating limited nutrients and space to themselves-an interference pathway with strong community-level effects [3] .

How to Apply the Concept: Step-by-Step Study Designs

Whether you are completing a lab, field project, or coursework assignment, you can systematically test competition hypotheses with the following approach.

Step 1: Define the limiting resource

Identify the most plausible limiting factor (light, nitrogen, water, nesting sites) using prior studies or pilot measurements.
Operationalize it with measurable indicators (e.g., photosynthetically active radiation for light; soil nitrate for nitrogen).

Step 2: Formulate hypotheses and predictions

Directional prediction: If species A reduces light by 40% at ground level, then species B’s growth rate and reproduction will decrease compared to unshaded controls.
Mechanism prediction: If interference is present, removing physical contact (barriers) should reduce the competitive effect relative to resource-depletion-only treatments.

Step 3: Experimental design

Replacement series
: Keep total density constant, vary the proportion of species A and B to infer competitive effects.
Addition series
: Add increasing densities of a competitor to focal individuals and measure response variables (growth, survival, fecundity).
Resource manipulation
: Add fertilizer or light to test whether effects are due to a specific limiting resource.
Barriers and spacing
: Use mesh or root barriers to separate interference from exploitation pathways.

Step 4: Measurement and analysis

Track survival, growth rates, biomass, reproductive output, and resource levels through time.
Use competition indices (e.g., relative competition intensity) and simple models (e.g., logistic growth; Lotka-Volterra competition) for inference. Many curricula introduce these models to link mechanism with outcome [3] .

Step 5: Interpret with coexistence theory

Ask whether niche differentiation, environmental fluctuations, or spatial heterogeneity enable coexistence despite strong competition.
Consider apparent competition if predator or pathogen dynamics track the abundance of one competitor.

Alternatives when experiments are constrained

Observational studies with natural gradients (light gaps, nutrient hotspots).
Before-after designs around disturbances (e.g., canopy opening).
Meta-analysis of published datasets to test general patterns.

Common Challenges and Practical Solutions

Challenge: Identifying the truly limiting resource

Solution
: Apply targeted resource additions (light filters, water supplementation, nutrient additions) singly and in combination to diagnose limitation. Use factorial designs to separate co-limitation vs. single-resource control [1] .

Challenge: Separating interference from exploitation

Solution
: Use physical partitions (root exclusion tubes, above-ground cages) to prevent direct contact while allowing shared resources, and compare to open treatments. Chemical assays or activated carbon in soils can test allelopathic effects [3] .

Challenge: Extrapolating lab results to nature

Solution
: Combine controlled experiments with field validation across spatial and temporal variation. Acknowledge that strict competitive exclusion is less common in heterogeneous real-world systems, which supports cautious generalization [2] .

Applying Insights in Coursework, Labs, and Fieldwork

Coursework : When asked to define competition, use a precise statement: Competition is an interaction where organisms share a limiting resource, reducing survivorship, growth, or reproduction for all involved. Then classify the interaction type (intra- vs. interspecific) and the mechanism (interference, exploitation, or apparent). Cite peer-reviewed or textbook-aligned resources to substantiate definitions [1] [3] .

Labs : Design experiments that manipulate density or resource levels and quantify fitness components. Use standardized metrics (e.g., per capita growth rates) and consider model fitting to estimate competition coefficients introduced in standard ecology curricula [3] .

Fieldwork : Map resource distributions and competitor abundances; apply partial removals or exclosures where permitted; track responses across seasons. Interpret patterns with coexistence frameworks and be explicit about uncertainty.

Key Takeaways

Competition is a
âˆ’/âˆ’
interaction driven by shared
limiting resources
that reduce fitness for both parties [1] [2] .
It occurs within and between species and operates via interference , exploitation , and sometimes apparent competition dynamics [1] [3] .
Competition influences natural selection , community structure , and can promote niche partitioning and biodiversity under many conditions [2] [4] .

References

[1] LibreTexts (2024). Introduction and Types of Competition.

[2] Wikipedia (n.d.). Competition (biology).

[3] University of Maryland (n.d.). Competition: definitions, types, and models.

[4] Crowther Lab (n.d.). Competition: an unavoidable aspect of life on Earth.