Why the Fuzzy Green Patch on Stale Bread Is Not a Plant
Learn the defining features of fungi and their nutrition, distinguish Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes, understand what places organisms in Plantae and Animalia, and compare viruses, viroids and lichens.
What do mushrooms, mould and yeast have in common?
A button mushroom, the fuzzy mould on stale bread and the yeast that makes bhatura dough rise look nothing alike. Yet all three are fungi — neither plants nor animals, but a kingdom of their own.
Around the edges of the five-kingdom system sit stranger entities too: viruses that live only inside cells, and lichens that are two organisms working as one.
This part covers the features of fungi, the classes of fungi, Kingdoms Plantae and Animalia, and viruses, viroids and lichens.
Around the edges of the five-kingdom system sit stranger entities too: viruses that live only inside cells, and lichens that are two organisms working as one.
This part covers the features of fungi, the classes of fungi, Kingdoms Plantae and Animalia, and viruses, viroids and lichens.
What are the defining features of Kingdom Fungi?
Fungi are eukaryotic heterotrophs whose cell walls contain chitin; most are built from thread-like hyphae forming a network called mycelium, and they feed as saprophytes, parasites or symbiotic partners.
Body structure.
- Hyphae — long, thin threads; together they form a mycelium
- Coenocytic hyphae — continuous tubes with many nuclei and no cross-walls
- Septate hyphae — divided by cross-walls called septa
- Yeast is an exception — it is unicellular
Nutrition:
- Saprophytic — absorb food from dead, decaying matter
- Parasitic — live on plants or animals, such as Puccinia, which causes rust in wheat
- Symbiotic — with algae in lichens, and with plant roots in mycorrhiza
Reproduction. Vegetatively by fragmentation, fission or budding; asexually by spores such as conidia, sporangiospores or zoospores; sexually by oospores, ascospores or basidiospores. In some fungi, two nuclei share one cell for a while — the dikaryotic stage — before they fuse.
An everyday example. White or green fuzz on pickles and bread during the monsoon is fungal mycelium feeding on the food as a saprophyte.
The substance. Fungi are not plants — they have no chlorophyll, their walls are chitin rather than cellulose, and they cannot make their own food.
Body structure.
- Hyphae — long, thin threads; together they form a mycelium
- Coenocytic hyphae — continuous tubes with many nuclei and no cross-walls
- Septate hyphae — divided by cross-walls called septa
- Yeast is an exception — it is unicellular
Nutrition:
- Saprophytic — absorb food from dead, decaying matter
- Parasitic — live on plants or animals, such as Puccinia, which causes rust in wheat
- Symbiotic — with algae in lichens, and with plant roots in mycorrhiza
Reproduction. Vegetatively by fragmentation, fission or budding; asexually by spores such as conidia, sporangiospores or zoospores; sexually by oospores, ascospores or basidiospores. In some fungi, two nuclei share one cell for a while — the dikaryotic stage — before they fuse.
An everyday example. White or green fuzz on pickles and bread during the monsoon is fungal mycelium feeding on the food as a saprophyte.
The substance. Fungi are not plants — they have no chlorophyll, their walls are chitin rather than cellulose, and they cannot make their own food.
How do Phycomycetes, Ascomycetes, Basidiomycetes and Deuteromycetes differ?
The four classes are separated by how their mycelium is built and how they produce spores: Phycomycetes have coenocytic mycelium and zygospores, Ascomycetes form ascospores in sacs, Basidiomycetes form basidiospores on club-shaped basidia, and Deuteromycetes show only asexual reproduction.
- Phycomycetes — moist places and water; aseptate, coenocytic mycelium; asexual spores inside sporangia; sexual zygospores. Examples: Mucor, Rhizopus (bread mould), Albugo (a parasite of mustard)
- Ascomycetes (sac fungi) — unicellular like yeast or multicellular like Penicillium; septate mycelium; asexual conidia on conidiophores; sexual ascospores in sacs called asci. Examples: Aspergillus, Claviceps, Neurospora
- Basidiomycetes — mushrooms, bracket fungi and puffballs; septate mycelium; usually no asexual spores and no sex organs, with two body cells fusing instead; sexual basidiospores on a basidium. Examples: Agaricus (mushroom), Ustilago (smut), Puccinia (rust)
- Deuteromycetes (imperfect fungi) — only asexual reproduction known, by conidia; septate mycelium; many are decomposers. Examples: Alternaria, Colletotrichum, Trichoderma
Worked example — sorting by spores.
- Spores in sacs — Ascomycetes
- Spores on a club-shaped cell — Basidiomycetes
- Zygospores with no cross-walls in hyphae — Phycomycetes
An everyday example. Button mushrooms sold in vegetable markets are Agaricus, a basidiomycete.
The substance. Deuteromycetes is a temporary group — once the sexual stage of a fungus is found, it is moved to Ascomycetes or Basidiomycetes.
- Phycomycetes — moist places and water; aseptate, coenocytic mycelium; asexual spores inside sporangia; sexual zygospores. Examples: Mucor, Rhizopus (bread mould), Albugo (a parasite of mustard)
- Ascomycetes (sac fungi) — unicellular like yeast or multicellular like Penicillium; septate mycelium; asexual conidia on conidiophores; sexual ascospores in sacs called asci. Examples: Aspergillus, Claviceps, Neurospora
- Basidiomycetes — mushrooms, bracket fungi and puffballs; septate mycelium; usually no asexual spores and no sex organs, with two body cells fusing instead; sexual basidiospores on a basidium. Examples: Agaricus (mushroom), Ustilago (smut), Puccinia (rust)
- Deuteromycetes (imperfect fungi) — only asexual reproduction known, by conidia; septate mycelium; many are decomposers. Examples: Alternaria, Colletotrichum, Trichoderma
Worked example — sorting by spores.
- Spores in sacs — Ascomycetes
- Spores on a club-shaped cell — Basidiomycetes
- Zygospores with no cross-walls in hyphae — Phycomycetes
An everyday example. Button mushrooms sold in vegetable markets are Agaricus, a basidiomycete.
The substance. Deuteromycetes is a temporary group — once the sexual stage of a fungus is found, it is moved to Ascomycetes or Basidiomycetes.
What places organisms in Plantae and Animalia, and why do some resist neat placement?
**Plantae contains eukaryotic, mostly autotrophic organisms with chlorophyll and cellulose cell walls, while Animalia contains multicellular eukaryotic heterotrophs without cell walls that usually ingest their food; organisms that mix these features, such as Euglena and insectivorous plants, show the boundaries are not perfectly sharp.
Kingdom Plantae: algae, bryophytes, pteridophytes, gymnosperms and angiosperms; cellulose walls; alternation of generations between gametophyte and sporophyte stages.
Kingdom Animalia: heterotrophic, holozoic nutrition (ingesting food); food stored as glycogen or fat; a definite growth pattern; most can move; mainly sexual reproduction.
Borderline cases:
- Euglena — has chloroplasts like a plant but no cell wall and swims with flagella like an animal; placed in Protista
- Insectivorous plants such as bladderwort and the Venus flytrap trap insects for extra nitrogen, but they still photosynthesise — so they remain plants
- Cuscuta is a parasitic plant with little chlorophyll that draws food from its host
An everyday example. Amarbel (Cuscuta) — yellow threads draped over hedges and ber trees — is a plant living as a parasite.
The substance. Mode of nutrition alone cannot fix an organism's kingdom**; cell walls, cell type and body plan matter too.
Kingdom Plantae: algae, bryophytes, pteridophytes, gymnosperms and angiosperms; cellulose walls; alternation of generations between gametophyte and sporophyte stages.
Kingdom Animalia: heterotrophic, holozoic nutrition (ingesting food); food stored as glycogen or fat; a definite growth pattern; most can move; mainly sexual reproduction.
Borderline cases:
- Euglena — has chloroplasts like a plant but no cell wall and swims with flagella like an animal; placed in Protista
- Insectivorous plants such as bladderwort and the Venus flytrap trap insects for extra nitrogen, but they still photosynthesise — so they remain plants
- Cuscuta is a parasitic plant with little chlorophyll that draws food from its host
An everyday example. Amarbel (Cuscuta) — yellow threads draped over hedges and ber trees — is a plant living as a parasite.
The substance. Mode of nutrition alone cannot fix an organism's kingdom**; cell walls, cell type and body plan matter too.
How do viruses, viroids and lichens compare as entities outside the five kingdoms?
Viruses are non-cellular particles of DNA or RNA inside a protein coat that can multiply only inside living cells; viroids are even simpler, with free RNA and no protein coat; and lichens are partnerships between an alga and a fungus living as a single body.
Viruses:
- Outside a cell they are inert and can even be crystallised
- Genetic material is either RNA or DNA, never both
- Capsid — the protein coat, made of subunits called capsomeres, arranged in helical or polyhedral shapes
- Plant viruses usually carry single-stranded RNA; bacteriophages usually double-stranded DNA
- Diseases include mumps, influenza and herpes in humans, and mosaic, leaf curling and yellowing in plants
Viroids: free RNA without a protein coat, with RNA of low molecular weight; they cause potato spindle tuber disease.
Lichens:
- Algal partner (phycobiont) — makes food by photosynthesis
- Fungal partner (mycobiont) — provides shelter and absorbs water and minerals
- Lichens are sensitive pollution indicators — they do not grow well in polluted air
Worked example — spot the entity. A particle with a protein coat and DNA that multiplies only inside bacteria is a bacteriophage; a bare RNA molecule causing potato disease is a viroid.
An everyday example. Grey-green crusty patches on old stone walls and tree bark are lichens.
The substance. Viruses show life-like behaviour only inside a host cell, which is why they sit outside the five-kingdom system.
Viruses:
- Outside a cell they are inert and can even be crystallised
- Genetic material is either RNA or DNA, never both
- Capsid — the protein coat, made of subunits called capsomeres, arranged in helical or polyhedral shapes
- Plant viruses usually carry single-stranded RNA; bacteriophages usually double-stranded DNA
- Diseases include mumps, influenza and herpes in humans, and mosaic, leaf curling and yellowing in plants
Viroids: free RNA without a protein coat, with RNA of low molecular weight; they cause potato spindle tuber disease.
Lichens:
- Algal partner (phycobiont) — makes food by photosynthesis
- Fungal partner (mycobiont) — provides shelter and absorbs water and minerals
- Lichens are sensitive pollution indicators — they do not grow well in polluted air
Worked example — spot the entity. A particle with a protein coat and DNA that multiplies only inside bacteria is a bacteriophage; a bare RNA molecule causing potato disease is a viroid.
An everyday example. Grey-green crusty patches on old stone walls and tree bark are lichens.
The substance. Viruses show life-like behaviour only inside a host cell, which is why they sit outside the five-kingdom system.
Exam tip
What earns full marks on fungi, viruses and lichens?
Tie every fungal class to its spore type and one example, and every non-cellular entity to what it lacks.
- Fungi: chitin walls, hyphae forming mycelium; saprophytic, parasitic, symbiotic
- Phycomycetes: coenocytic, zygospores — Rhizopus, Albugo
- Ascomycetes: asci — Penicillium, Aspergillus, yeast
- Basidiomycetes: basidia — Agaricus, Puccinia, Ustilago
- Deuteromycetes: only asexual — Alternaria, Trichoderma
- Viruses: capsid of capsomeres, DNA or RNA; viroids: RNA, no coat; lichens: alga + fungus
The trap. Saying viroids have a protein coat like viruses. Viroids are bare RNA.
- Fungi: chitin walls, hyphae forming mycelium; saprophytic, parasitic, symbiotic
- Phycomycetes: coenocytic, zygospores — Rhizopus, Albugo
- Ascomycetes: asci — Penicillium, Aspergillus, yeast
- Basidiomycetes: basidia — Agaricus, Puccinia, Ustilago
- Deuteromycetes: only asexual — Alternaria, Trichoderma
- Viruses: capsid of capsomeres, DNA or RNA; viroids: RNA, no coat; lichens: alga + fungus
The trap. Saying viroids have a protein coat like viruses. Viroids are bare RNA.
Did you know
Why does bread and bhatura dough rise?
Mix a little yeast into dough and leave it in a warm place, and within an hour or two the dough puffs up.
Yeast is a single-celled fungus, an ascomycete. It feeds on the sugars in the flour and, without much oxygen, breaks them down by fermentation, releasing carbon dioxide gas and a little alcohol.
The gas gets trapped as tiny bubbles in the stretchy dough, making it rise, and baking or frying drives the alcohol away. A kingdom that spoils food on one shelf helps make it on another.
Yeast is a single-celled fungus, an ascomycete. It feeds on the sugars in the flour and, without much oxygen, breaks them down by fermentation, releasing carbon dioxide gas and a little alcohol.
The gas gets trapped as tiny bubbles in the stretchy dough, making it rise, and baking or frying drives the alcohol away. A kingdom that spoils food on one shelf helps make it on another.
Exam relevance
How are fungi, viruses and lichens tested in NEET?
Kingdom Fungi, the borderline organisms and the non-cellular entities complete Biological Classification in NEET Biology.
What gets asked. Matching fungal genera with their class, identifying spore types, features of Plantae and Animalia, why Euglena and insectivorous plants are unusual, the structure of viruses, how viroids differ from viruses, and the roles of the two partners in lichens. Fungi and viruses return in Microbes in Human Welfare and Human Health and Disease in Class 12.
Question types. Match-the-column lists and statement-based questions.
The trap that costs marks. **Placing Alternaria or Trichoderma in Ascomycetes** instead of Deuteromycetes.
What gets asked. Matching fungal genera with their class, identifying spore types, features of Plantae and Animalia, why Euglena and insectivorous plants are unusual, the structure of viruses, how viroids differ from viruses, and the roles of the two partners in lichens. Fungi and viruses return in Microbes in Human Welfare and Human Health and Disease in Class 12.
Question types. Match-the-column lists and statement-based questions.
The trap that costs marks. **Placing Alternaria or Trichoderma in Ascomycetes** instead of Deuteromycetes.
Key takeaways
What must you be able to do from this part?
- Fungi: chitin walls; septate or coenocytic hyphae; saprophytic, parasitic (Puccinia) or symbiotic (lichens, mycorrhiza)
- Classes: Phycomycetes — Rhizopus; Ascomycetes — Aspergillus, yeast; Basidiomycetes — Agaricus; Deuteromycetes — Alternaria
- Plantae and Animalia: cellulose walls and chlorophyll versus holozoic, wall-less cells; Euglena and insectivorous plants blur the line
- Outside the kingdoms: viruses with capsomeres and DNA or RNA; viroids with bare RNA; lichens as alga plus fungus
Name the class of each: Ustilago, Mucor, Claviceps and Colletotrichum — and give the spore feature that decides each answer.
- Classes: Phycomycetes — Rhizopus; Ascomycetes — Aspergillus, yeast; Basidiomycetes — Agaricus; Deuteromycetes — Alternaria
- Plantae and Animalia: cellulose walls and chlorophyll versus holozoic, wall-less cells; Euglena and insectivorous plants blur the line
- Outside the kingdoms: viruses with capsomeres and DNA or RNA; viroids with bare RNA; lichens as alga plus fungus
Name the class of each: Ustilago, Mucor, Claviceps and Colletotrichum — and give the spore feature that decides each answer.