Fungus is ancient in origin, but its exact evolution is left to conjecture.
From the available fossil records, it is estimated that they originated approximately one billion years ago. The original fungi are most likely to have been single-celled organisms living in the water.
There is no particular atmosphere that is conducive to their existence. They can be found in extreme temperatures, both dry and wet surfaces, and thrive in the dark and light.
Early Evolution
From the aquatic fungi that were unicellular organisms with flagella, fungi now lack flagella and are mostly terrestrial. The kingdom is now a diverse family of heterotrophic eukaryotes (organisms with a distinct nucleus). The structure of their cell organization ranges from unicellular to complex.
The term 'fungi' was coined by Carolus Linnaeus, the Father of Modern Taxonomy. 'Fungi' is the plural of Latin 'Fungus', which means 'mushroom'.
There is DNA evidence to prove that all fungi have a common ancestor. About 500 million years ago, fungi colonized land, a little later than plants.
About 250 million years later, they are known to have been abundant in many places and could even have been a dominant form of life on Earth.
Where do fungi grow?
The expanse of the fungal kingdom is vast and extensive, but they can't be seen either because they are too small or are hidden inside their habitat.
Fungi can grow in warm temperatures ranging from 70 - 150°F (21 - 65°C) or as low as 32°F (0° C). They are found in plenty in woods and meadows, leading to a misconception that they need a dark and wet environment to grow. But they also grow in the seemingly inhospitable tundra!
Symbiotic relationships between a fungus and plant roots are called mycorrhiza. Mycorrhizal fungi grow on the roots of particular trees; or multiple types of trees.
A cross-sectional study of fungal environments indicates that the environmental suitability for fungi is species-specific.
They are mostly found in dark, moist conditions, which is why a majority of the fungal species are found on the forest floor, where the decaying debris facilitates copious growth of fungi.
Physical Features & Behavior
Fungi can be single-celled or multicellular.
Most fungi, except yeast cells, have a filamentous structure. Each of these filaments is called hypha, which together forms the mycelium.
The cell wall of fungi comprises a cell membrane with various proteins and a protective layer of chitin and glucans. Chitin helps provide the necessary structural strength to the cell walls of fungi, preventing desiccation and access to predators. Glucans are the most abundant polysaccharides in the cell wall and provide resistance to the cell wall.
Fungi have a dense, clear nucleus surrounded by a clear membrane.
They also do not have mouths (like animals) to ingest food. Fungi cannot perform photosynthesis (like plants) as they lack chlorophyll. Historically classified as plants, fungi formed the 'third kingdom' due to this distinct feature.
Organisms such as slime molds were once confused with fungi as they are both eukaryotic organisms. Slime mold cells have cellulose, not chitin, and they move on decomposing matter, unlike fungi, which are immobile.
Life Cycle
Fungi can reproduce sexually or asexually.
The phases of sexual reproduction are the spore phase, mycelium phase, and meiosis. The fruiting body of the fungus produces spores that travel to a suitable environment and produce mycelium, which then undergoes meiosis when the cell splits in two.
Whether a fungus opts for sexual or asexual reproduction is impacted by the environment. If at the mycelium stage, it doesn't find a suitable mycelium, it produces mitospores that are identical to the parent. These produce new mycelium, which further reproduces.
Epigeous fruitbodies grow on the ground, and hypogeous fruit bodies grow underground. Evidence shows that hypogeous fungi evolved from epigeous fungi but lost the ability to disperse spores. They propagate through consumption and defecation by animals.
Imperfect fungi are those species of fungi whose reproduction is only known to be asexual. They were classified as Deuteromycota, though they are no longer formally accepted as a taxon.
A fungus' life cycle initiates with the spore and ends with propagation. A fully grown fungus releases spores whose cells divide and spread into hyphae. When two sets of hyphae meet, they create a new cell, dikaryon.
The fruiting body into which a dikaryon develops is called a mushroom. The nuclei in the mushroom form cells with a single set of chromosome-haploid cells that create spores through meiosis. Further, fruiting does not happen, and the remnants of the parent fungus decompose.
An important factor that affects the life of fungi is climate change. There has been a marked change in fungal reproduction, geographic distribution, physiology, and activity in the past few decades. The ecosystem functions, in turn, will be impacted by the changes in fungal growth.
Uses & Harmful Effects
Fungi have a prominent impact-both, positive and negative, on human life: food, medicine, farming, research, and so on.
Penicillin notatum, the producer of the antibiotic penicillin, yeast, black mold, edible mushrooms such as portobello mushrooms, medicinal mushrooms such as Lion's Mane (Hericium erinaceus) mycorrhizal fungi come under the same umbrella of useful fungi.
The hallucinogenic fungi, Amanita muscaria, dermatophytes that cause diseases such as ringworm, athlete's foot, and jock itch, and a wide range of parasitic fungi are some of the species of fungi that are harmful to life. Fungal infections can be opportunistic (taking advantage of a weak system), localized, or primary.
While fungal infections in healthy people can be cured, they can be life-threatening if immunity is compromised.
Without mycorrhizal fungi, most vegetation would not survive. Organic farming is supported vastly by these fungi that have a symbiotic relationship with root systems. Mycorrhizal fungi also help prevent water stress in plants.
The fungal species Aspergillus terreus can produce as much as 88g/L of itaconic acid used to make plastic car parts, synthetic rubber, and a Lego. If not for the master decomposers that fungi are, life would not be possible!
Even before man knew what fungus was, he used the yeast, Saccharomyces cerevisiae, to ferment alcohol! The alcohol thus fermented was not only inebriating but also antibacterial.
It is believed that Pope Clement VII died of eating the world's most poisonous mushroom, Ammanita phalloides, known as the Death Cap. The Holy Roman Emperor Charles VI, and even the Buddha himself, are amongst those believed to be fungi victims!
FAQs
What is special about fungi?
Fungi are responsible (with bacteria) for releasing carbon, oxygen, nitrogen, and phosphorus into the soil and atmosphere. They decompose organic matter, making way for new life.
How long do fungi live for?
The life span of a fungus differs according to species. They can live from a day to a week or month. However, the honey mushroom (Armillaria ostoyae) is considered the largest and oldest organism on Earth. It is estimated to be around 8,650 years old!
Why do fungi need water?
Fungi release enzymes to break down complex materials in the environment. Moisture is required to release these enzymes to help in the process of absorptive nutrition.
Can fungi move?
No, fungi cannot move. So they create spores that travel to find a suitable environment.
Are fungi animals or plants?
The fungal kingdom is a third kingdom that is neither animal nor plant.
Where did fungi come from?
The earliest fungi are aquatic fungi dating back to a billion years, but they colonized land about 500 million years ago. Since all known fungi are monophyletic, it is concluded that they come from the same ancestor.
Does fungus need oxygen?
Most fungi need oxygen, but there are species, such as Chytridiomycota, whose metabolism can be disrupted or even killed by ingesting oxygen.
Can fungi live without water?
Fungi cannot grow or reproduce without water, but they can survive until favorable conditions are created.
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Bachelor of Science specializing in Botany, Master of Science specializing in Clinical Research and Regulatory Affairs
Sridevi ToletyBachelor of Science specializing in Botany, Master of Science specializing in Clinical Research and Regulatory Affairs
With a Master's degree in clinical research from Manipal University and a PG Diploma in journalism from Bharatiya Vidya Bhavan, Sridevi has cultivated her passion for writing across various domains. She has authored a wide range of articles, blogs, travelogues, creative content, and short stories that have been published in leading magazines, newspapers, and websites. Sridevi is fluent in four languages and enjoys spending her spare time with loved ones. Her hobbies include reading, traveling, cooking, painting, and listening to music.
Shreya YadavBachelor of Arts specializing in Psychology
Shreya has developed a diverse set of skills through her experience in client servicing, email marketing, content and e-commerce management, digital marketing, and creative content writing. Her educational background includes a Bachelor's degree in Psychology from Indira Gandhi National Open University, Delhi. Shreya's passion for ongoing learning and development is a testament to her commitment to excellence.
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