10 public questions tagged with this topic.
The mycelium of Phycomycetes is aseptate and coenocytic. This means that the hyphae lack cross walls and contain multinucleated cytoplasm within a continuous tube.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Fungi - Phycomycetes Ascomycetes Basidiomycetes
Deuteromycetes are called imperfect fungi because only their asexual or vegetative phases are known. They reproduce by asexual spores called conidia.
Ref: NCERT Class 11 Biology Chapter 2: Biological Classification Fungi - Phycomycetes Ascomycetes Basidiomycetes
Oomycetes excluded from true fungi and placed in Oomycota within Stramenopila, Chromista supergroup based on converging ultrastructural, biochemical and molecular divergences. Cell walls contain cellulose and β-1,3, β-1,6 glucans with negligible chitin contrasting fungal chitin-glucan architecture. Vegetative mycelium diploid throughout, mitochondria bearing tubular cristae not flattened, lysine biosynthesis via diaminopimelate pathway not aminoadipate, and biflagellate zoospores with anterior tinsel and posterior whiplash flagella driving motility. Life cycle diplontic producing oogonia and antheridia forming thick-walled oospores through oogamous sexual reproduction aligning closer to brown algae.
Ref: Campbell Biology 12th ed. Chapter 28 Protistan Relatives Oomycota; NCBI Taxonomy Oomycetes APSnet Table 1
Deuteromycetes traditionally designated Fungi Imperfecti represent artificial form-group where sexual teleomorphic phase remains undiscovered despite extensive culture attempts, so classification relies on asexual anamorph characteristics solely. Lack of ascocarps, basidiocarps or zygosporangia means primary taxonomic criteria of sexual reproduction cannot apply. Mycelium usually septate with dolipore or simple septa, reproduction via conidia or sterile mycelia only. Molecular phylogenetics using ITS, LSU rDNA now nests most deuteromycetes within Ascomycota and Basidiomycota indicating secondary loss of sexuality, yet practical identification continues using absence of observed sexual reproduction as diagnostic imperfect designation.
Ref: Webster & Weber Introduction to Fungi 3rd ed. Deuteromycetes; Campbell Biology 12th ed. Chapter 31
Fungal systematics traditionally relied on morphology of sexual reproductive structures because vegetative hyphae convergent across phyla and nutritional modes overlap all being absorptive heterotrophs. Presence of ascus containing ascospores defines Ascomycota, basidium bearing basidiospores defines Basidiomycota, zygosporangium with zygospore defines Zygomycota sensu lato. Asexual conidial morphology secondary and variable. Habitat varies widely within phyla, nutrition all absorptive osmotrophic, cell wall composition all chitinous except oomycetes excluded as stramenopiles. Therefore reproductive structures provide most stable phylogenetically informative character reflecting evolutionary innovation in meiosporangial architecture.
Ref: Campbell Biology 12th ed., Chapter 31: Fungal Classification Based on Reproductive Structures; NCERT Class 11 Biological Classification
Vegetative hyphae septation pattern serves important taxonomic criterion distinguishing fungal phyla. Zygomycetous fungi within Mucoromycota possess coenocytic aseptate hyphae lacking regular cross-walls, nuclei moving freely through continuous cytoplasm except when delimiting reproductive organs. Ascomycota and Basidiomycota exhibit septate hyphae with perforate septa containing pores. Deuteromycota artificial group also septate. Absence of septa facilitates rapid cytoplasmic streaming and growth but increases vulnerability to injury. Therefore group lacking septa in vegetative stage among given choices is Zygomycota, reflecting early divergence before evolution of regular septation.
Ref: Campbell Biology 12th ed., Chapter 31: Zygomycota Aseptate Coenocytic; NCERT Class 11 Phycomycetes Coenocytic Mycelium; NCBI Mucoromycota
Zygomycota sensu lato defined by sexual reproduction involving fusion of compatible progametangia from opposite mating types positive and negative forming thick-walled zygosporangium containing single zygospore. Karyogamy of haploid nuclei followed by meiosis yields haploid spores after dormancy period. Zygospore withstands desiccation due to melanized multi-layered wall with sporopollenin. Ascomycota produce ascospores, Basidiomycota basidiospores, conidia are asexual mitospores. Zygospore formation via conjugation, hence name conjugation fungi, differentiates this group despite modern split into Mucoromycota and Zoopagomycota maintaining characteristic zygosporogenesis. Meiosis inside zygosporangium after dormancy ensures genetic variation and dispersal of haploid progeny adapting to changing environmental conditions.
Ref: Campbell Biology 12th ed., Chapter 31: Zygomycota Zygospores Formation; NCERT Class 11 Phycomycetes; NCBI: Zygosporogenesis Review
Chytridiomycota are only true fungi retaining flagellated zoospores with single posterior whiplash flagellum similar to opisthokont sperm architecture, representing ancestral character retained from opisthokont ancestor. Flagellum inserts posteriorly pushing cell forward with undulatory propulsion. Ascomycota and Basidiomycota completely lack motile cells, Zygomycota sensu lato produce non-motile sporangiospores. Zoospore ultrastructure with kinetosome, microtubular roots and rumposome marks chytrids distinct. This trait places them as basal fungal lineage diverging before loss of flagellum, crucial for phylogenetic placement and ecological role in aquatic decomposition and amphibian disease.
Ref: Campbell Biology 12th ed., Chapter 31: Chytridiomycota Flagellum Posterior; NCBI: Chytrid Flagellar Evolution - Medina et al.; NCERT
According to the NCERT textbook, Alternaria, Colletotrichum, and Trichoderma are the prime examples explicitly listed under the class Deuteromycetes (imperfect fungi), where many act as critical decomposers of litter. In sharp contrast, Ustilago (which famously causes smut disease in crops) and Puccinia (causing rust) are standard examples provided under the class Basidiomycetes. Therefore, Ustilago does not belong to Deuteromycetes.
Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.3 Kingdom Fungi
Deuteromycetes act as a temporary taxonomic placeholder in mycology. According to NCERT, they are famously termed 'imperfect fungi' strictly because only their asexual or vegetative phases of reproduction are currently known. The 'perfect' (sexual) stages have either not yet been discovered or may have been lost evolutionarily. Once the sexual stage of a member is discovered, it is properly reclassified to Ascomycetes or Basidiomycetes.
Ref: NCERT Class 11 Biology > Chapter 2: Biological Classification > 2.3 Kingdom Fungi
