Kingdom Fungi

True fungi are grouped into classes in NCERT Class 11, Chapter 2 (Biological Classification) using the morphology of the mycelium, the mode of spore formation and the type of fruiting bodies. Ascomycetes, the sac fungi, produce sexual spores called ascospores formed endogenously inside sac-like structures known as asci, which are typically arranged within fruiting bodies called ascocarps. Penicillium, Aspergillus, Neurospora and the unicellular yeast Saccharomyces are classic ascomycetes. Basidiomycetes are incorrect because they form basidiospores produced exogenously on club-shaped basidia, as seen in mushrooms, puffballs and rusts. Phycomycetes are wrong as they are lower fungi with aseptate, coenocytic mycelium that reproduce by zoospores or aplanospores, not ascospores, with examples like Mucor and Rhizopus. Deuteromycetes, the imperfect fungi, are placed there only when sexual reproduction is unknown; once a sexual ascus stage is discovered they are reassigned, often to Ascomycetes. Many ascomycetes are economically and scientifically valuable, since Penicillium yields antibiotics and Neurospora is a model organism in genetic and biochemical research. A consistency check confirms that the presence of ascospores inside asci is the diagnostic feature uniquely pointing to Ascomycetes among the four classes.