written by: J.Sace•edited by: Rebecca Scudder•updated: 9/25/2010
Did you know that fungi have different ecological roles? They are decomposers of organic matter; symbionts of plants and animals; natural enemies of pests; food for animals; and bioremediation agents.
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Fungi (singular: fungus) are single-celled or multicellular eukaryotic organisms that reproduce through spores and live by absorbing nutrients from organic matter. They were originally considered to belong to the plant kingdom because of their similarities in morphology and growth habit. But with the introduction of molecular techniques in taxonomy, fungi were reclassified into their own separate kingdom: Kingdom Fungi. Taxonomists discovered major differences of fungi from plants: fungi don’t have chlorophyll, unlike plants; and the cell wall of fungi is made up of chitin instead of cellulose. Yeasts are single-celled fungi while mushrooms are multicellular fungi.
According to scientists, there are approximately 1.5 million species of fungi in the planet but only 5 percent of them have been given proper identification. That figure makes fungi as one of the most biologically diverse organisms in the planet. Fungi have a fundamental role in nutrient cycling due to their ability to decompose organic matter. They have adapted to form symbiotic relationship with plants and animals for billion years. Many organisms depend on fungi for survival. Continue reading to learn more about the ecological importance of fungi.
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Fungi as Decomposers
Fungi join bacteria as the primary decomposers in different ecosystems. They feed on the organic remains of dead plants. They release special enzymes that break down lignin, a structurally complex substance in wood. Because of their ability to break down wood, fungi are considered the major wood decomposers in forests. To absorb organic matter, fungi release acids to melt organic matter, and then they suck the acid back together with the melted organic matter. Decomposing organic matter is considered by ecologists as the major ecological role of fungi.
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The symbiotic association between a vascular plant root and fungi is called mycorrhiza. In this association, fungi colonize the roots of a plant and gain access to their tissues. The fungi build a connection to the roots in such a way that they can exchange nutrients with each other. Plants provide mycorrhizal fungi shelter and a supply of carbohydrates; in return, mycorrhizal fungi improve the plant’s absorption capabilities for water and nutrients. Mycorrhizal fungi have a larger surface-area ratio compared to roots, so they have higher absorptive capacity for water and minerals. They make it easier for plants to absorb water and minerals in soils that are dry and with low mineral concentration. Without mycorrhiza, it would be difficult for plants to absorb water and minerals from such soils. It is estimated that about 90% of plants depends on mycorrhizal fungi for survival.
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Fungi do not only associate with plants but also with insects. Some groups of ants, termites, and beetles cultivate fungi for food. There are also insects that deposit their eggs to growing fungi; they learned that the fungi can provide nutrients for their developing larvae. Microscopic fungi (yeasts) have been found in the gut of insects, but their role is not yet clear. Scientists hypothesize that they might play a role in insect nutrition.
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Fungi as Food
Fungi are not only eaten by insects but also by other larger animals. Some species of beaver, wolverine, squirrels, rodents, kangaroos, wallabies, and bears were found to eat fungi. These animals have adapted to carefully identify non poisonous fungi (mushrooms). We humans also eat different types of edible and nutritious mushrooms.
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Fungi for Pest Control
Fungi can be the future natural alternative for pesticides and herbicides. Some fungi species are natural enemies of insects, weeds, mites, nematodes, and other fungi that cause crop disease. Scientists call these fungi species biopesticides because of their ability to kill or suppress the growth of organisms that damage economically important crops such as corn, barley, soybean, rice, and wheat. Scientists are actively discovering and studying fungal species that can be potentially useful biopesticides for different crops.
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Fungi for Bioremediation
Bioremediation (biological remediation) is simply the use of biological agents to clean and restore a polluted environment. Bacteria and plants are the most commonly used biological agents to clean contaminated land and water. Through the years, mycologists discovered certain species of fungi (e.g. white-rot fungi) that are able to degrade soil pollutants such as insecticides, herbicides, heavy metals, creosote, coal tars, and hydrocarbon fuels. These fungal species secrete enzymes that neutralize the pollutants.