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An interaction between two species that benefits both. Individualsthat interact with mutualists experience higher sucess than those that do not.Hence, behaving mutualistically is advantageous to the individual, and it doesnot require any concern for the well-being of the partner. At one time,mutualisms were thought to be rare curiosities primarily of interest to naturalhistorians. However, it is now believed that every species is involved in oneor more mutualisms. Mutualisms are thought to lie at the root of phenomena asdiverse as the origin of the eukaryotic cell, the diversification of floweringplants, and the pattern of elevated species diversity in tropical forests.

Mutualisms generally involve an exchange of substances or services thatorganisms would find difficult or impossible to obtain for themselves. Forinstance, Rhizobium bacteria found in nodules on the roots of manylegume (bean) species fix atmospheric nitrogen into a form (NH3)that can be taken up by plants. The plant provides the bacteria with carbon inthe form of dicarboxylic acids. The carbon is utilized by the bacteria asenergy for nitrogen fixation. Consequently, leguminous plants often thrive innitrogen-poor environments where other plants cannot persist. Anotherwell-known example is lichens, in which fungi take up carbon fixed duringphotosynthesis of their algae associates.

A second benefit offered within some mutualisms is transportation. Prominentamong these mutualisms is biotic pollination, in which certain animals visitflowers to obtain resources and return a benefit by transporting pollen betweenthe flowers they visit. A final benefit is protection from one's enemies.For example, ants attack the predators and parasites of certain aphids inexchange for access to the aphids' carbohydrate-rich excretions(honeydew).

Another consideration about mutualisms is whether they are symbiotic. Twospecies found in intimate physical association for most or all of theirlifetimes are considered to be in symbiosis. Not all symbioses are mutualistic;symbioses may benefit both, one, or neither of the partners.

Mutualisms can also be characterized as obligate or facultative (dependingon whether or not the partners can survive without each other), and asspecialized or generalized (depending on how many species can confer thebenefit in question).

Two features are common to most mutualisms. First, mutualisms are highlyvariable in time and space. Second, mutualisms are susceptible to cheating.Cheaters can be individuals of the mutualist species that profit from theirpartners' actions without offering anything in return, or else otherspecies that invade the mutualism for their own gain.

Mutualism has considerable practical significance. Certain mutualisms playcentral roles in humans' ability to feed the growing population. It hasbeen estimated that half the food consumed is the product of bioticpollination. See Ecology, Plant pathology


Mutual interactions between two species that are beneficial to both species.
References in periodicals archive ?
These questions focus on mutual relationship between Prime Minister and interior minister.
Lootah said the ministry has launched several media initiatives that aim to enhance community awareness about political participation and development, and has also organised in the past a training programme for media representatives to maintain a strong mutual relationship, which helps media personnel to clearly understand the message to be delivered to the audience.
He also invited the Egyptian counterpart to Yemen to resume the meetings of the Yemeni-Egyptian Joint Higher Committee, affirming Yemen's keenness on strengthening mutual relationship of fraternity, love, and cooperation with Egypt.
This is only the beginning of a long path of mutual relationship which we hope will develop into greater achievements and further mutual understanding and friendship," she added.
As expatriates, we are looking for better life, at the same time we are also contributing to the development of Qatar, so it is a mutual relationship where we all benefit," he noted.
A report to Middlesbrough Council's executive says the basis of the development model at the Sheffield site has been to attract the research and development activities across particular supply chains and foster a mutual relationship with university-based specialists.
Williams F1's CEO Alex Burns said: "This is a logical partnership given Williams and Hispania's mutual relationship with Cosworth.
As part of the mutual relationship with central Asia, China is trying to increase its trade volume with Uzbekistan.
Commerce and government; considered in their mutual relationship.
Nowadays that all difficulties have been passed by the bravery of Iranian nation and while the Iraqi dictator Saddam Hossain has been finally overthrown, it seems that an effective mutual relationship is going to be formed between Iran and Iraq, basing upon the two sides' political and cultural commons.
The visit is intended to "consolidate security and stability in Iraq and to strengthen the mutual relationship between the two countries on all levels, including trade and culture," according to a statement released by Talabani's office.
Amid deep concern over his independence-leaning position, Chen is expected to reaffirm his push in his next four years for a ''peace and stability interaction framework'' to govern bilateral activities across the Taiwan Strait and a set of new guidelines to ensure a peaceful development of the mutual relationship, said a senior official who asked not to be named.

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