Problem : What characteristic of yeasts makes them identifiable as ascomycota?

The presence of an ascus in the sexual reproductive cycle of yeasts makes them identifiable as ascomycota.

Problem : Describe the haploid and diploid phases of ascomycota.

The mycelia of ascomycota are haploid. The hyphae of the fruiting body are also haploid. After plasmogamy, the ascogonium and ascogonious hyphae are binucleate, but still haploid. In the ascus, fusion takes place, making this a diploid cell. After meiosis, the ascus produces haploid spores.

Problem : In what stuctures do plasmogamy and karyogamy take place in ascomycota

Plasmogamy takes place between the ascogonium and antheridium through the trichogyne. Karyogamy takes place in the ascus.