TOEFL Reading Practice Test #20

Fungi are a diverse group of organisms that play critical roles in ecosystems, often working behind the scenes to sustain life on Earth. Neither plant nor animal, fungi form their own unique kingdom, encompassing thousands of species that include molds, yeasts, and mushrooms. Though they are often overlooked, fungi are essential for decomposition, nutrient cycling, and forming symbiotic relationships with other organisms.

One of the most vital roles fungi play is in decomposition, where they break down organic matter into simpler compounds. Fungi release enzymes that digest complex materials such as wood, leaves, and animal remains, recycling nutrients back into the soil. This process is crucial for maintaining soil fertility and enabling plants to access essential elements like nitrogen and phosphorus. Without fungi, organic material would accumulate, and ecosystems would become clogged with waste. For example, fungi such as species of Penicillium and Aspergillus specialize in decomposing organic debris, help facilitate the natural recycling process.

In addition to their role as decomposers, fungi are integral to nutrient cycling. Mycorrhizal fungi, which form associations with plant roots, enhance the uptake of water and nutrients from the soil. In exchange, plants supply the fungi with carbohydrates produced through photosynthesis. These partnerships, found in up to 90% of plant species, are so effective that they significantly boost plant growth and productivity. Certain fungi also play a role in nitrogen fixation, helping convert atmospheric nitrogen into a form usable by plants. This intricate collaboration between fungi and plants highlights their interdependence.

Fungi also interact with other organisms through symbiotic and parasitic relationships. Lichens, for instance, are a combination of fungi and algae or cyanobacteria, in which the fungi provide structure and moisture while the algae perform photosynthesis. This mutualism allows lichens to colonize harsh environments like rocky surfaces and arid deserts. On the other hand, some fungi are parasitic, infecting plants, animals, and even humans. Pathogenic fungi like Candida albicans can cause infections in humans, while others such as Puccinia species devastate agricultural crops by causing diseases like wheat rust.

Beyond their ecological importance, fungi contribute significantly to human industries. Penicillin, the world’s first antibiotic, was derived from the Penicillium fungus, revolutionizing medicine. Fungi are also used in food production, from the fermentation of bread and beer to the cultivation of mushrooms as a protein source. More recently, researchers have begun exploring fungi’s potential in biotechnology, including bioplastics and biofuel production.

However, fungi face threats from climate change, habitat destruction, and pollution. Rising temperatures and shifting ecosystems can disrupt fungal communities, potentially harming their vital functions. For example, mycorrhizal fungi are sensitive to changes in soil composition and temperature, which could reduce their effectiveness in supporting plants. Conserving fungal diversity is therefore essential for preserving ecological balance and ensuring the continuation of their numerous benefits to humans and the environment.