Kingdom Fungi- Structure, Characteristics, Classification, Classifications, Concepts

Edited By Irshad Anwar | Updated on Jun 13, 2025 09:52 AM IST

Fungi form a distinct kingdom of eukaryotic organisms that are heterotrophic and play an important role in maintaining ecological balance. Fungi lack chlorophyll and cannot perform photosynthesis like plants. They obtain their nutrients through absorption and break down organic matter in their surroundings by utilising strong enzymes. Fungi are highly variable in form and environment, from the minute yeasts to the great mushrooms, and they occur in most as hot and humid areas where decaying plant and animal matter is abundant.

This Story also Contains

What is Fungi?
Cell Structure of Fungi
Characteristics of Fungi
Classification of Fungi
Fungal Diseases
Beneficial Fungi
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Kingdom Fungi- Structure, Characteristics, Classification, Classifications, Concepts

The form of most fungi is an aggregation of thread-like bodies called hyphae, which form the mycelium. Fungi are formed sexually and asexually, and frequently by the creation of spores that aid in their dispersal. They are a significant ecological component as decomposers, symbionts (in mycorrhizae and lichens), and even pathogens. Fungi also possess enormous economic value. They are the producers of food components, including antibiotics such as penicillin, and have widespread usage in the fermentation industry. At the same time, some are edible or are used in the preparation of food, such as bread, cheese, and alcoholic beverages.

What is Fungi?

Fungi perform important functions as the recyclers of matter and nutrients in the terrestrial and aquatic systems. Further, the fungi also become mutualistic partners of plants by helping in the acquisition of nutrients and increasing the plant’s ability to withstand stress.

The use and classification of fungi started with early naturalists and taxonomists; it progressed from those associated with plants to the modern and more scientific basis of morphology and genetics. That is why it is critical to know about their ecological significance and context to comprehend their value to nature, farming, pharmaceuticals, and bioengineering in today’s world.

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Cell Structure of Fungi

Fungi possess unique cellular features that distinguish them within the biological kingdom:

Feature	Fungal Cells	Significance
Cell Type	Eukaryotic cells are well-developed cells with a true nucleus and DNA enclosed by a nuclear membrane.	Distinguishes fungi from prokaryotes (e.g., bacteria).
Cell Wall Composition	The cell wall is made primarily of chitin (a polymer of N-acetylglucosamine).	Unlike plant cell walls (cellulose) Chitin provides rigidity and protection.
Adaptation Role	The chitinous cell wall provides mechanical strength and helps fungi survive diverse and harsh conditions.	Unique among eukaryotes, enabling fungi to thrive in varied environments.

Characteristics of Fungi

There are different aspects of fungi which are important

Aspect	Type / Process	Description	Significance
Nutrition	Saprophytic	Most fungi break down dead organic matter and recycle nutrients into ecosystems.	Key role in nutrient cycling and improving soil fertility.
	Parasitic	Derive nutrients from living organisms and can cause diseases in plants, animals, and humans.	Important in agriculture, silviculture, and medicine due to pathogenic effects.
	Mutualistic	Form beneficial associations (e.g., mycorrhizae, endophytes) with plants or other organisms.	Enhance plant nutrient uptake and stress tolerance.
Reproduction	Asexual -Spores	Asexual spores form by mitosis, are dispersed by wind, water, or animals, and germinate under favourable conditions.	Allows rapid colonisation of new habitats.
	Asexual- Budding	Seen in yeasts, a small outgrowth (bud) forms on the parent, develops into a new cell.	Simple, efficient reproduction in unicellular fungi like yeast.
	Sexual- Spores	Fusion of gametes forms a diploid zygote → meiosis → four haploid spores.	Generates genetic variation Adapt fungi to new environments.
	Sexual - Mating Types	Mating types (+ and –) ensure compatibility for sexual reproduction Nuclei fuse, forming a zygote.	Maintains species diversity and promotes genetic recombination.
Growth & Development	Hyphal growth	Hyphae are thread-like structures that branch out and secrete enzymes to decompose organic compounds.	Helps in nutrient absorption and soil aeration.
	Mycelium formation	An interwoven network of hyphae forms the mycelium, the vegetative body of the fungus.	Allows extensive substrate colonisation and efficient nutrient absorption.

Classification of Fungi

Fungi are classified into several major divisions (phyla) based on their reproductive structures and genetic characteristics:

Phylum / Group	Sexual Reproduction	Asexual Reproduction	Examples	Special Feature
Ascomycota (Sac fungi)	Sexual spores are formed inside a sac-like structure called an ascus.	Commonly by conidia (asexual spores)	Yeast, Penicillium, Tuber (truffles)	Ascus formation is distinctive of this group.
Basidiomycota (Club fungi)	Sexual spores called basidiospores are produced on a club-shaped basidium.	Less prominent, mainly sexual reproduction	Agaricus (mushroom), rust fungi, smut fungi	Characterised by basidia that bear basidiospores externally.
Zygomycota (Zygote fungi)	Sexual reproduction occurs via thick-walled zygospores formed from fused hyphae.	Asexual reproduction by sporangiospores	Rhizopus (bread mould)	Forms zygospores during sexual phase; fast-growing saprophytes.
Deuteromycota (Imperfect fungi)	No known sexual reproduction.	Reproduce by asexual spores	Aspergillus, Candida	Called imperfect fungi due to the absence of an observed sexual cycle.

Fungal Diseases

Fungi cause a variety of diseases in plants, animals, and humans, impacting agriculture, ecosystems, and public health:

Pathogen Type	Disease	Cause	Characteristic Features
Plant Pathogens	Rusts	Fungi infecting leaves and stems	Reddish-brown, powdery spots on plant parts
	Smuts	Parasitic fungi (often Ascomycotina) infecting grains and grasses	The black, sooty appearance of infected tissues
	Blights	Often bacterial, but can involve a fungal association	Yellowing, withering, and rotting of plant parts (e.g., potatoes, tomatoes)
Animal / Human Pathogens	Athlete’s Foot	Dermatophyte fungi infect the skin of the feet	Itching, redness, peeling of skin
	Ringworm	Various fungi infect the skin or scalp	Circular rashes on the skin or scalp
	Candidiasis	Candida species (e.g., Candida albicans)	Causes oral thrush, vaginal infections; affects mouth, genitals, skin

Beneficial Fungi

Fungi provide numerous benefits to humans and the environment through various applications:

Edible mushrooms like Agaricus (button mushroom) and Shiitake provide protein, fibre, B vitamins, selenium, and potassium.
Agaricus is widely utilised in cooking techniques for its mild, bland flavour.
Shiitake is valued for flavour and potential therapeutic properties, including anti-inflammatory activity.
Medicinal fungi like Penicillium (penicillin) and Tolypocladium inflatum (cyclosporine) produce important medicines.
Certain fungi are involved in bioremediation by decomposing pollutants, poisonous wastes, oils, and fuels in soil and water.

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