Competition (biology) - AbsoluteAstronomy.com

Competition is an interaction

Biological interaction

Biological interactions are the effects organisms in a community have on one another. In the natural world no organism exists in absolute isolation, and thus every organism must interact with the environment and other organisms...

between organism

Organism

In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s or species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, in which the fitness

Fitness (biology)

Fitness is a central idea in evolutionary theory. It can be defined either with respect to a genotype or to a phenotype in a given environment...

of one is lowered by the presence of another. Limited

Limiting factor

A limiting factor or limiting resource is a factor that controls a process, such as organism growth or species population, size, or distribution. The availability of food, predation pressure, or availability of shelter are examples of factors that could be limiting for an organism...

supply of at least one resource (such as food

Food

Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

, water

Water

Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, and territory

Territory (animal)

In ethology the term territory refers to any sociographical area that an animal of a particular species consistently defends against conspecifics...

) used by both is required. Competition both within and between species

Species

is an important topic in ecology

Ecology

Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

, especially community ecology. Competition is one of many interacting biotic

Biotic component

Biotic components are the living things that shape an ecosystem. A biotic factor is any living component that affects another organism, including animals that consume the organism in question, and the living food that the organism consumes. Each biotic factor needs energy to do work and food for...

and abiotic factors that affect community

Community (ecology)

In ecology, a community is an assemblage of two or more populations of different species occupying the same geographical area. The term community has a variety of uses...

structure. Competition among members of the same species is known as intraspecific competition

Intraspecific competition

Intraspecific competition is a particular form of competition in which members of the same species vie for the same resource in an ecosystem...

, while competition between individuals of different species is known as interspecific competition

Interspecific competition

Interspecific competition, in ecology, is a form of competition in which individuals of different species compete for the same resource in an ecosystem...

. Competition is not always straightforward, and can occur in both a direct and indirect fashion..

According to the competitive exclusion principle

Competitive exclusion principle

In ecology, the competitive exclusion principle, sometimes referred to as Gause's law of competitive exclusion or just Gause's law, is a proposition which states that two species competing for the same resources cannot coexist if other ecological factors are constant...

, species less suited to compete for resources should either adapt

Adaptation

An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

or die out

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

. According to evolutionary theory, this competition within and between species for resources plays a critical role in natural selection

Natural selection

Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

, however, competition may play less of a role than expansion among larger groups such as families..

By mechanism

The following terms describe mechanism

Mechanism (biology)

In biology --and in science in general-- a mechanism is a complex object or, more generally, a process that produces a regular phenomenon. For example, natural selection is one of the mechanisms of biological evolution, other being genetic drift, biased mutation, and gene flow; competition,...

s by which competition occurs, which can generally be divided into direct and indirect. These mechanisms apply equally to intraspecific and interspecific competition.

Interference competition:Occurs directly between individuals via aggression

Aggression

In psychology, as well as other social and behavioral sciences, aggression refers to behavior between members of the same species that is intended to cause humiliation, pain, or harm. Ferguson and Beaver defined aggressive behavior as "Behavior which is intended to increase the social dominance of...

etc. when the individuals interfere with foraging, survival, reproduction of others, or by directly preventing their physical establishment in a portion of the habitat.
Exploitation competition:Occurs indirectly through a common limiting resource which acts as an intermediate. For example, use of resources depletes the amount available to others, or they compete for space. Also known as exploitative competition.
Apparent competition:Occurs indirectly between two species which are both preyed upon by the same predator. For example, species A and species B are both prey of predator C. The increase of species A will cause the decrease of species B because the increase of As would increase the number of predator Cs which in turn will hunt more of species B.

Intraspecific competition

Intraspecific competition occurs when members of the same species vie for the same resource

Natural resource

Natural resources occur naturally within environments that exist relatively undisturbed by mankind, in a natural form. A natural resource is often characterized by amounts of biodiversity and geodiversity existent in various ecosystems....

s in an ecosystem. For example, two tree

Tree

A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s growing close together will compete for light

Light

Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...

above ground, and water

Water

and nutrient

Nutrient

A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...

s in the soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

. Therefore, getting less resources, they will usually perform less well than if they grew by themselves. Although in this situation it may actually be more useful to think in terms of resource availability than competition. Adaptations to such an environment include growing taller, (where the specific prediction provided by the competition model is that all species in such a situation will grow as tall as possible). or developing a larger root

Root

In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...

system (where the specific prediction is that all species in the system will develop very deep root systems). The real question is whether these predictions are evidenced by our observations of the natural world...

Interspecific competition

Interspecific competition may occur when individuals of two separate species share a limiting resource in the same area. If the resource cannot support both populations, then lowered fecundity

Fecundity

Fecundity, derived from the word fecund, generally refers to the ability to reproduce. In demography, fecundity is the potential reproductive capacity of an individual or population. In biology, the definition is more equivalent to fertility, or the actual reproductive rate of an organism or...

, growth, or survival may result in at least one species. Interspecific competition has the potential to alter population

Population

A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

s, communities and the evolution of interacting species.

An example among animals could be the case of cheetah

Cheetah

The cheetah is a large-sized feline inhabiting most of Africa and parts of the Middle East. The cheetah is the only extant member of the genus Acinonyx, most notable for modifications in the species' paws...

s and lion

Lion

The lion is one of the four big cats in the genus Panthera, and a member of the family Felidae. With some males exceeding 250 kg in weight, it is the second-largest living cat after the tiger...

s; since both species feed on similar prey, they are negatively impacted by the presence of the other because they will have less food, however they still persist together, despite the prediction that under competition one will displace the other. In fact, lions sometimes steal prey items killed by cheetahs. Potential competitors can also kill each other, and this phenomenon is called 'intraguild predation

Intraguild predation

Intraguild predation, or IGP, is the killing and eating of potential competitors. This interaction represents a combination of predation and competition, because both species utilize the same prey resources and also benefit from preying upon one another...

'. For example, in southern California coyotes often kill and eat gray foxes and bobcats, all three carnivores sharing the same stable prey (small mammals).

Competition has been observed between individuals, populations and species, but there is little evidence that competition has been the driving force in the evolution of large groups. For example, between reptiles and mammals. Mammals lived beside reptiles for many millions of years of time but were unable to gain a competitive edge until dinosaurs were devastated by the K-T Extinction.

Evolutionary strategies

In evolutionary contexts, competition is related to the concept of r/K selection theory, which relates to the selection

Natural selection

of traits which promote success in particular environments. The theory originates from work on island biogeography

Island biogeography

Island biogeography is a field within biogeography that attempts to establish and explain the factors that affect the species richness of natural communities. The theory was developed to explain species richness of actual islands...

by the ecologists Robert MacArthur

Robert MacArthur

Robert Helmer MacArthur was an American ecologist who made a major impact on many areas of community and population ecology....

and E. O. Wilson

E. O. Wilson

Edward Osborne Wilson is an American biologist, researcher , theorist , naturalist and author. His biological specialty is myrmecology, the study of ants....

.

In r/K selection theory

R/K selection theory

In ecology, r/K selection theory relates to the selection of combinations of traits in an organism that trade off between quantity or quality of offspring...

, selective pressures are hypothesised to drive evolution in one of two stereotyped directions: r- or K-selection. These terms, r and K, are derived from standard ecological algebra

Algebra

Algebra is the branch of mathematics concerning the study of the rules of operations and relations, and the constructions and concepts arising from them, including terms, polynomials, equations and algebraic structures...

, as illustrated in the simple Verhulst equation of population dynamics

Population dynamics

Population dynamics is the branch of life sciences that studies short-term and long-term changes in the size and age composition of populations, and the biological and environmental processes influencing those changes...

where r is the growth rate of the population

Population

(N), and K is the carrying capacity

Carrying capacity

The carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available in the environment...

of its local environmental setting. Typically, r-selected species exploit empty niches

Ecological niche

In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

, and produce many offspring

Offspring

In biology, offspring is the product of reproduction, of a new organism produced by one or more parents.Collective offspring may be known as a brood or progeny in a more general way...

, each of whom has a relatively low probability

Probability

Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we arenot certain. The proposition of interest is usually of the form "Will a specific event occur?" The attitude of mind is of the form "How certain are we that the event will occur?" The...

of surviving to adulthood. In contrast, K-selected species are strong competitors in crowded niches, and invest

Parental investment

In evolutionary biology, parental investment is any parental expenditure that benefits one offspring at a cost to parents' ability to invest in other components of fitness...

more heavily in much fewer offspring, each of whom has a relatively high probability of surviving to adulthood.

By mechanism

Intraspecific competition

Interspecific competition

Evolutionary strategies

See also