Medical Academy named after S.I.  Georgievsky of  Vernadsky  CFU

BY
SIVAKUMAR KALAIVANNANILAVAN
194-B

existence concerns the competition or battle for resources needed to

live. It can refer to human society, or to organisms in nature. The concept is ancient, and the term struggle for existence was in use by the end of the 18th century. From the 17th century onwards the concept was associated with a population exceeding resources, an issue shown starkly in Thomas Robert Malthus’ An Essay on the Principle of Population which drew on Benjamin Franklin's Observations Concerning the Increase of Mankind, Peopling of Countries, etc

broader sense, and chose the term as the title to

the third chapter of On the Origin of Species published in 1859. Using Malthus’s idea of the struggle for existence, Darwin was able to develop his view of adaptation, which was highly influential in the formulation of the theory of natural selection. In addition, Alfred Wallace independently used the concept of the struggle for existence to help come to the same theory of evolution. Later, T.H. Huxley further developed the idea of the struggle for existence.

but he did agree that there was a struggle for

existence in nature. Huxley also recognized that a struggle for existence existed between competing ideas within the minds of people engaged in intellectual discussion.
This view is an early example of what was later described as meme theory.

in the western world, there were other interpretations of the

struggle for existence, especially by Peter Kropotkin in Russia. Also, the struggle for existence was questioned in the United States in the 1930s, as the idea of cooperation among organisms became popular. More recently, it has been argued that the struggle for existence is not as important on macroevolutionary time scales.

to the interactions between the organisms which is called as

the competition
Competition is an interaction between organisms or species in which both the organisms or species are harmed. Limited supply of at least one resource (such as food, water, and territory) used by both can be a factor.

in ecology, especially community ecology. Competition is one of many

interacting biotic and abiotic factors that affect community structure.
There are two types of completion in the nature they are:
Interspecific competiton
Intraspecific competition

members of the same species compete for limited resources. This

leads to a reduction in fitness for both individuals, but the most fit individual survives and is able to reproduce. By contrast, interspecific competition occurs when members of different species compete for a shared resource. Members of the same species have rather similar requirements for resources, whereas different species have a smaller contested resource overlap, resulting in intraspecific competition generally being a stronger force than interspecific competition.

any other resource which is required for survival or reproduction.

The resource must be limited for competition to occur; if every member of the species can obtain a sufficient amount of every resource then individuals do not compete and the population grows exponentially. Prolonged exponential growth is rare in nature because resources are finite and so not every individual in a population can survive, leading to intraspecific competition for the scarce resources.

the quantity of resources available for each individual, reducing the

per capita fitness in the population. As a result, the growth rate of a population slows as intraspecific competition becomes more intense, making it a negatively density dependent process. The falling population growth rate as population increases can be modelled effectively with the logistic growth model
Intraspecific competition does not just involve direct interactions between members of the same species (such as male deer locking horns when competing for mates) but can also include indirect interactions where an individual depletes a shared resource (such as a grizzly bear catching a salmon that can then no longer be eaten by bears at different points along a river).

in which individuals of different species compete for the same

resources in an ecosystem (e.g. food or living space). This can be contrasted with mutualism, a type of symbiosis. Competition between members of the same species is called intraspecific competition.

form of competition in which one species consumes and either

reduces or more efficiently uses a shared limiting resource and therefore depletes the availability of the resource for the other species. Thus, it is an indirect interaction because the competing species interact via a shared resource.
Interference competition is a form of competition in which individuals of one species interacts directly with individuals of another species via antagonistic displays or more aggressive behavior
In a review and synthesis of experimental evidence regarding interspecific competition, Schoener described six specific types of mechanisms by which competition occurs, including consumptive, preemptive, overgrowth, chemical, territorial, and encounter. Consumption competition is always resource competition, but the others are cannot always be regarded as exclusively exploitative or interference.

where large trees dominate the canopy and thus allow little

light to reach smaller competitors living below. These interactions have important implications for the population dynamics and distribution of both species.

Which arose from mathematical analysis and simple competition models states

that two species that use the same limiting resource in the same way in the same space and time cannot coexist and must diverge from each other over time in order for the two species to coexist. One species will often exhibit an advantage in resource use. This superior competitor will out-compete the other with more efficient use of the limiting resource. As a result, the inferior competitor will suffer a decline in population over time. It will be excluded from the area and replaced by the superior competitor

been less documented than niche separation or competitive exclusion, it

does occur. In an experiment involving zooplankton in artificial rock pools, local extinction rates were significantly higher in areas of interspecific competition. In these cases, therefore, the negative effects are not only at the population level but also species richness of communities.

on community composition and structure. Niche separation of species, local

extinction and competitive exclusion are only some of the possible effects. In addition to these, interspecific competition can be the source of a cascade of effects that build on each other. An example of such an effect is the introduction of an invasive species to the United States, purple-loosestrife. This plant when introduced to wetland communities often outcompetes much of the native flora and decreases species richness, food and shelter to many other species at higher trophic levels. In this way, one species can influence the populations of many other species as well as through a myriad of other interactions. Because of the complicated web of interactions that make up every ecosystem and habitat, the results of interspecific competition are complex and site-specific.

in conservation efforts is often hard to accomplish because the

tools with which we measure diversity and redundancy cannot be used interchangeably. Due to this, recent empirical work most often analyzes the effects of either functional diversity or functional redundancy, but not both. This does not create a complete picture of the factors influencing ecosystem production. In ecosystems with similar and diverse vegetation, functional diversity is more important for overall ecosystem stability and productivity. Yet, in contrast, functional diversity of native bee species in highly managed landscapes provided evidence for higher functional redundancy leading to higher fruit production, something humans rely heavily on for food consumption. A recent paper has stated that until a more accurate measuring technique is universally used, it is too early to determine which species, or functional groups, are most vulnerable and susceptible to extinction. Overall, understanding how extinction affects ecosystems, and which traits are most vulnerable can protect ecosystems as a whole

or collection of organisms, that share alike characteristics within a

community. Ideally, the lifeforms would perform equivalent tasks based on domain forces, rather than a common ancestor or evolutionary relationship. This could potentially lead to analogous structures that overrule the possibility of homology. More specifically, these beings produce resembling effects to external factors of an inhabiting system. Due to the fact that a majority of these creatures share an ecological niche, it is practical to assume they require similar structures in order to achieve the greatest amount of fitness. This refers to such as the ability to successfully reproduce to create offspring, and furthermore sustain life by avoiding alike predators and sharing meals.

in the same ecosystem fill similar roles, which results in

a sort of "insurance" in the ecosystem. Redundant species can easily do the job of a similar species from the same functional niche. This is possible because similar species have adapted to fill the same niche overtime. Functional redundancy varies across ecosystems and can vary from year to year depending on multiple factors including habitat availability, overall species diversity, competition among species for resources, and anthropogenic influence.

production. It is not always known how many species occupy

a functional niche, and how much, if any, redundancy is occurring in each niche in an ecosystem. It is hypothesized that each important functional niche is filled by multiple species. Similar to functional diversity, there is no one clear method for calculating functional redundancy accurately, which can be problematic. One method is to account for the number of species occupying a functional niche, as well as the abundance of each species. This can indicate how many total individuals in an ecosystem are performing one function.

in a large proportion of conservation and ecological research. As

the human population increases, the need for ecosystem function subsequently increases. In addition, habitat destruction and modification continue to increase, and suitable habitat for many species continues to decrease, this research becomes more important. As the human population continues to expand, and urbanization is on the rise, native and natural landscapes are disappearing, being replaced with modified and managed land for human consumption. Alterations to landscapes are often accompanied with negative side effects including fragmentation, species losses, and nutrient runoff, which can effect the stability of an ecosystem, productivity of an ecosystem, and the functional diversity and functional redundancy by decreasing species diversity.

the species diversity, and functional overlap, leaving the ecosystem and

organisms in it vulnerable. Specifically, bee species, which we rely on for pollination services, have both lower functional diversity and species diversity in managed landscapes when compared to natural habitats, indicating that anthropogenic change can be detrimental for organismal functional diversity, and therefore overall ecosystem functional diversity. Additional research demonstrated that the functional redundancy of herbaceous insects in streams varies due to stream velocity, demonstrating that environmental factors can alter functional overlap.

debate whether preserving specific species, or functional traits is a

more beneficial approach for the preservation of ecosystem function. Higher species, diversity can lead to an increase in overall ecosystem productivity, but does not necessarily insure the security of functional overlap. In ecosystems with high redundancy, losing a species (which lowers overall functional diversity) will not always lower overall ecosystem function due to high functional overlap, and thus in this instance it is most important to conserve a group, rather than an individual. In ecosystems with dominant species, which contribute to a majority of the biomass output, it may be more beneficial to conserve this single species, rather than a functional group.