Kingdom Fungi

Key Points to Remember

Fungi are eukaryotic organisms that live as saprophytes, parasites, or symbionts.
They:

• Lack chlorophyll and do not photosynthesize.
• Have chitinous cell walls instead of cellulose.
• Reproduce by spores, budding, or hyphal fusion.
• Play major roles in nutrient recycling, fermentation, and antibiotic production.

Keywords

Fungi, Chitin, Hyphae, Saprophytic, Spores, Penicillium, Yeast.

Kingdom Fungi – Structure, Types, and Importance

Kingdom Fungi includes a large group of eukaryotic, heterotrophic, and mostly multicellular organisms that absorb nutrients from their surroundings. Unlike plants, fungi do not perform photosynthesis and have cell walls made of chitin, not cellulose.

They play an essential role in decomposition, food production, and medicine, while some can also cause diseases in plants and animals.

Characteristics of Fungi

1. Cell Structure

• Eukaryotic: Possess a true nucleus and membrane-bound organelles.
• Cell wall: Made of chitin, not cellulose.
• Unicellular & multicellular: Yeast is unicellular; most others form multicellular structures.
• Hyphae & Mycelium: Thread-like filaments (hyphae) collectively form a mycelium, the main body of the fungus.

2. Heterotrophic Mode of Nutrition

Fungi absorb nutrients directly from organic matter.

• Saprophytic: Feed on dead and decaying matter (e.g., Mucor, Rhizopus).
• Parasitic: Live on or inside other organisms and cause diseases (e.g., Ringworm, Rust fungus).
• Symbiotic: Live in mutual relationships — e.g., Lichens (fungus + alga) and Mycorrhizae (fungus + plant roots).

3. Reproduction

• Asexual reproduction: Through fragmentation, budding, or spores.
• Sexual reproduction: Involves fusion of specialized hyphae from two compatible fungi.

Classification of Fungi

1. Phycomycetes (Lower Fungi)

• Found in soil, water, and damp environments.
• Asexual spores: Sporangiospores
• Sexual spores: Zygospores
• Examples: Mucor, Rhizopus (bread mold).

2. Ascomycetes (Sac Fungi)

• Produce sexual spores in a sac-like structure called ascus.
• Can be unicellular (yeast) or multicellular (Penicillium).
• Examples: Aspergillus, Penicillium, Saccharomyces (yeast).

3. Basidiomycetes (Club Fungi)

• Reproduce sexually by basidiospores on club-shaped structures called basidia.
• Examples: Mushrooms (Agaricus), Rust fungi, Puffballs.

4. Deuteromycetes (Imperfect Fungi)

• No sexual reproduction observed.
• Most are decomposers or disease-causing pathogens.
• Examples: Trichophyton (athlete’s foot), Alternaria.

Significance of Fungi

1. Ecological Importance

• Act as decomposers, recycling organic matter into nutrients for plants.
• Maintain ecosystem balance by breaking down dead organisms.

2. Food & Fermentation

• Yeast (Saccharomyces) helps produce bread, wine, and beer.
• Mushrooms serve as nutritious food sources.

3. Medicinal Value

• Penicillium produces the antibiotic penicillin, which revolutionized medicine.
• Some fungi are sources of vitamins and enzymes used in biotechnology.

4. Symbiotic Relationships

• Lichens (fungus + alga) contribute to soil formation.
• Mycorrhizae enhance nutrient absorption in plant roots.

5. Pathogenic Effects

• Cause diseases like ringworm, athlete’s foot, and plant rusts.

Conclusion

Fungi are vital to life on Earth — they recycle nutrients, produce food and medicines, and form beneficial relationships with plants. At the same time, some species can be harmful pathogens. Their versatility and ecological importance make fungi a key kingdom in biological studies.