All organisms in an ecosystem require specific resources to survive, grow, and reproduce. These resources are not limitless, and their finite nature inevitably leads to interactions among organisms as they strive to meet their needs. This scarcity profoundly influences the structure and dynamics of biological communities.
Defining Competition in Nature
Ecological competition describes an interaction between organisms where both require the same limited resources within an environment. This interaction results in a reduction in the fitness of all organisms involved, as the presence of one organism diminishes resources available to others. Resources are components of the environment necessary for survival and reproduction, such as food, water, shelter, light, and territory. Unlike environmental conditions like temperature or salinity, resources have the potential to become scarce, driving this struggle for existence.
Types of Ecological Competition
Competition in ecosystems manifests in two forms: intraspecific and interspecific.
Intraspecific competition occurs among individuals of the same species vying for identical limited resources. For instance, a dense stand of plants of the same age will compete strongly for resources like sunlight, water, and nutrients in the soil. Similarly, a group of zebras in a savannah will compete for the same patch of grass.
Interspecific competition, conversely, involves organisms from different species competing for the same limited resources. This type of competition arises when different species occupy overlapping ecological niches, meaning they utilize similar resources or inhabit similar areas. An example includes lions and leopards competing for the same prey animals in a shared hunting ground. Another instance is a taller tree species in a forest absorbing more sunlight, thereby reducing the light available to shorter, surrounding trees.
What Organisms Compete For
Organisms within an ecosystem compete for a variety of essential resources that are often in limited supply.
Food
Food provides energy and nutrients for growth and metabolic processes. When food becomes scarce, populations may struggle to survive or reproduce effectively.
Water
Water is a limiting factor, especially in terrestrial environments, where its availability can significantly impact the survival of both plants and animals. Access to water is important for physiological functions, growth, and reproduction.
Light
For plants, light is a resource for photosynthesis. In densely vegetated areas, such as forests, competition for sunlight can be intense, with taller plants often outcompeting shorter ones for access to light.
Space and Territory
Space or territory provides areas for shelter, nesting, foraging, or establishing a home range. Animals may compete for specific territories, while plants compete for sufficient soil space for root growth.
Mates
Within a species, individuals often compete for mates, a resource important for reproductive success.
Impacts of Competition on Ecosystems
Competition profoundly shapes the structure and dynamics of ecological communities, influencing species distribution, population sizes, and evolutionary trajectories.
Competitive Exclusion Principle
A key outcome of interspecific competition is the competitive exclusion principle. This posits that two species cannot indefinitely coexist if they compete for the same limited resource in the same niche. One species will inevitably outcompete the other, leading to the local extinction or displacement of the less successful competitor.
Resource Partitioning
To mitigate the effects of direct competition, species often evolve strategies like resource partitioning. This involves species adapting to use different resources, or the same resources in different ways, times, or places. For example, two bird species might feed on the same type of insect, but one might forage in the tree canopy while the other forages on the ground, thus reducing direct competition.
Evolutionary Force
Competition also serves as an evolutionary force, driving adaptations that enhance an organism’s ability to acquire resources, avoid competitors, or exploit new niches. This pressure can lead to the development of specialized traits.