Ecological competition occurs when living organisms, including animals, plants, bacteria and fungi, need the same limited resources to thrive in their shared environment.
Each organism has a specific place in the ecosystem known as its niche in biology. The purpose of specialization in a niche is to regulate competition.
An ecosystem could collapse if several species needed the same scarce resources to complete their life cycle.
Definition of Competition in Biology
Competition in biology is a term that describes how living organisms directly or indirectly seek resources.
Competition can occur within a species or between different species. The many types of competition include everything from dogs fighting over a bone to rutting stags locking horns in a fight to the death.
Even microscopic bacteria vigorously compete through various mechanisms, such as exploiting a particular resource needed by competitors, or using metabolic functions to make the external environment unsuitable for other bacterial species.
Competition examples are ubiquitous in the natural world. Competitive invasive species such as stink bugs, khapra beetles, green ash borers, garlic mustard, Asian carp, zebra mussels and Asiatic beetles can decimate native species and severely disrupt the ecosystem. Scientists estimate that lichen produce more than 500 biochemical compounds that kill microbes, control light and suppress plant growth.
Competition in community ecology sustains life and strengthens the gene pool. Better competitors are more likely to survive and pass on their advantageous genetic traits to offspring. Whether a characteristic is favorable or unfavorable depends on environmental conditions.
For instance, hooves are better adaptations than toes for running across open grasslands.
Competition Often Drives Adaptations
Reproduction is a driving motivator of living organisms. Many traits, characteristics and competitive behaviors have evolved to ensure continuation of the species.
For instance, female turkeys and peacocks prefer suitors with impressive tail feathers. Mating calls, mating dances and other mating rituals are also adaptations linked to reproductive success.
Gause’s Competitive Exclusion Principle
A stable ecosystem is regulated by counterbalancing forces. The competitive exclusion principle, developed by Russian scientist and mathematician G.F. Gause in the 1930s, states that two species cannot indefinitely hold the same spot in a niche because resources are finite.
Eventually, the best competitor will dominate, causing the other to move on or die off.
However, there can be subtle differences that may allow for peaceful coexistence. For example, similar species of seed-eating kangaroo rats can still live in the same small area because one species prefers feeding on hard ground and the other likes sandy spots. Therefore, the competing rats avoid running into each other.
Additionally, there are mitigating factors that may enable stronger and weaker competitors to live side by side. Such scenarios can occur when the dominant species is under siege by predators or resource needs change.
Competition can also be reduced if the subordinate species feeds on the leftovers of the dominant species rather than fighting them for prey.
Types of Competition and Examples
Competition in biology is tied to supply and demand. Individuals of a species will fiercely compete for whatever they need from the environment to survive and enjoy reproductive success.
Plants compete with each other for light exposure, temperature, humidity, pollinators, soil nutrients and growing space. Microbes compete for chemical substrates. Animals fight over territory, water, food, shelter and prospective mates.
Intraspecific competition involves direct competition between members of the same species. Competition can be keen within a species that shares an ecological niche because they demand identical resources. Competition is less of an issue when organisms live in different niches and use slightly different resources.
A common competition in biology example is the vocal and territorial male Northern cardinal that chases away other male cardinals interloping on its breeding grounds.
Interspecific competition occurs between members of different species that desire the same things, such as food, shelter and water. Direct competition is a type of struggle that involves species or organisms directly interacting with one another. Vultures and wolves both go after a fresh moose carcass, for instance.
Indirect competition does not involve direct confrontation; for example, non-migratory sparrows may build nests in bluebird houses before the migratory bluebirds return to their home from the previous season.
Exploitation competition is a common dominance strategy found in many different areas. Stronger competitors monopolize resources and deny access to competitors. For example, whitetail deer herds can eat all the vegetation in the understory. Loss of forest food and habitat threaten the survival of small birds like indigo buntings, robins and warblers, as well as large birds like wild turkeys that nest in ferns.
Interference competition happens when one organism devises a way of interfering with another organism’s access to mutually desired resources. For example, walnut trees produce deadly toxins in the soil, and pine trees change the natural pH of the soil to keep competitors at bay. In the animal kingdom, a hungry coyote frightens away buzzards and crows feasting on carrion.
Nature regulates population size and dynamics. When population growth is unsustainable, organisms are more susceptible to disease that leads to death and starvation, and the birth rate drops.
Competition in biology is density-dependent, meaning that competition heats up when the number of competitors is high, and decreases when competitors are few in number.
Intraspecific competition in biology is particularly intense.
Competition can have consequences beyond the typical predator-and-prey interactions that keep populations in check. When a species loses food and habitat, it can become endangered or extinct. Hunting and urbanization has played a role in species loss.
For example, passenger pigeons once numbered in the billions from New York to California before they were hunted and forced out of their native nesting areas.
They are now extinct.
According to the American Museum of Natural History, the growing population of humans on the planet poses the biggest threat to other species. Humans exploit thousands of species and deplete limited natural resources to maintain comfortable lifestyles. Human over-consumption leaves fewer resources for other species that cannot compete with human activity.
Ongoing threats to the ecosystem include global warming, pollution, deforestation, over-fishing and introduction of invasive species.
Competition and Evolution
Competition plays a decisive role in natural selection and evolution. Well-adapted organisms have an edge in maintaining their spot in the ecosystem. Organisms with less favorable traits and characteristics decline in the population. Weaker competitors tend to die off before propagating their genes, or they relocate to a place where the odds of surviving and thriving appear more promising.
Character displacement is an evolutionary process of natural selection that supports divergence within a population. Generally, character displacement is more prevalent in areas where two competing species overlap. For example, Charles Darwin found evidence of ecological character displacement when he was studying ground finches in the Galapagos Islands.
To reduce competition for particular resources, finch species developed different sizes and shapes of beaks adapted to eating certain seed varieties that other species had trouble reaching or cracking.
According to The Washington Post, evolutionary change can happen much faster than previously believed. For instance, green anole lizards in Florida moved their habitat from low branches to high branches in trees in response to an invasion of brown anole lizards from Cuba.
In just 15 years, the green anole had developed sticky feet to help them cling to the treetops as a response to direct competition from another species that ate the same kind of food.
- The American Naturalist: Limiting Factors, Competitive Exclusion, and a More Expansive View of Species Coexistence
- Centennial Museum: Gause's Principle
- Science: Competition
- American Expedition!: Northern Cardinal Facts, Information, Photos & Artwork
- Izaak Walton League of America: The Dangers of Too Many Deer
- Princeton University: Gene Behind ‘Evolution in Action’ in Darwin’s Finches Identified
- The Washington Post: Competition Drove These Lizards to Evolve Big, Sticky Feet in Just 15 Years
- MMN.com: The Unexpectedly Weird and Beautiful World of Lichens
- American Society for Microbiology: Multifaceted Interfaces of Bacterial Competition
- Behavioral Ecology: Nowhere to Hide: Pumas, Black Bears, and Competition Refuges
- Smithsonian: The Passenger Pigeon
- American Museum of Natural History: What Is Biodiversity?
About the Author
Dr. Mary Dowd studied biology in college where she worked as a lab assistant and tutored grateful students who didn't share her love of science. Her work history includes working as a naturalist in Minnesota and Wisconsin and presenting interactive science programs to groups of all ages. She enjoys writing online articles sharing information about science and education. Currently, Dr. Dowd is a dean of students at a mid-sized university.