Differences in sexual structures, spores and reproductive strategies among fungal groups can be used for classification. The spore-containing structures, asci and basidia , have been used in the identification of ascomycetes and basidiomycetes 38
Some species may allow mating only between individuals of opposite mating type ( Heterothallic ), while others can mate and sexually reproduce with any other individual or itself( Homothalic ) Most fungi have both a haploid and diploid stage in their life cycles. In sexually reproducing fungi, compatible individuals may fuse their hyphae together into an interconnected network; a process, called anastomosis . Anastomosis is required for the initiation of the sexual cycle. Ascomycetes and basidiomycetes go through a dikaryotic stage , in which the nuclei inherited from the two fusing parents do not combine immediately but remain separate in the hyphal cells. Sexual reproduction in Ascomycetes In ascomycetes, dikaryotic hyphae of the spore-bearing tissue form a characteristic hook at the hyphal septum. During cell division , formation of the hook ensures proper distribution of the newly divided nuclei into the apical and basal hyphal compartments. An ascus is then formed, in which nuclear fusion occurs. Asci are embedded in an ascocarp, or fruiting body. 39
Nuclear fusion in the asci is followed immediately by meiosis and the production of ascospores . The ascospores may germinate and form a new haploid mycelium. Sexual reproduction in Basidiomycetes Sexual reproduction in basidiomycetes is similar to that of the ascomycetes. Compatible haploid hyphae fuse to produce a dikaryotic mycelium. A specialized anatomical structure, called a clamp connection , is formed at each hyphal septum. The clamp connection in the basidiomycetes is required for controlled transfer of nuclei during cell division, to maintain the dikaryotic stage with two genetically different nuclei in each hyphal compartment. A basidiocarp is formed in which club-like structures known as basidia generate haploid basidiospores after nuclear fusion and meiosis. The most commonly known basidiocarps are mushrooms, but they may also take other forms. Recent classification: Fungal Phylum Phylum Meaning Common name Distinguishing characteristics 1 Chytridiomyco Little pot Chytrids Cellulose in cell walls, 40
ta mushroom flagellated gametes 2 Deuteromycot a Second mushroom Imperfect fungi Unclassified fungi; only asexual reproduction observed 3 Zygomycota Yolk mushroom Zygomycetes Blend gametangia to form a zygosporangium 4 Glomeromycot a Ball mushroom None Form arbuscular mycorrhizae with plants 5 Ascomycota Bag/Wineskin Mushroom Sac fungi Produce spores in an ' ascus ' 6 Basidiomycota Basidium Mushroom Club Fungi Produce spores from a ' basidium ' CAT 3: TAKE AWAY ASSIGNMENT: 1O MARKS Write a term paper on recent classification of fungi: 1. Discribe of each phylum its Classes, Orders, and life cycles.
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