Answer 3
There is more variation within the Chytrids than the remaining fungi. Therefore,
the answer will rely on the remaining divisions. The principle differences
appear to be the responses following initiation of the sexual interaction.
Following recognition, hyphae of opposite mating types of Zygomycota anastomose
and form a sporangium within which forms the diploid zygospore. In Euascomycetes,
the response is a crozier which contains the diploid nucleus with branching
dikaryotic cells beneath. The diploid nucleus passes immediately into meiosis,
with formation of the ascus containing haploid ascospores. In yeasts the
process is simpler. Plasmogamy is immediately followed by karyogamy, followed
by meiosis. In Basidiomycota, separation of plasmogamy and karyogamy complicates
interpretation. Some fungi have basidiospore formation analogous to Euascomycetes.
Formation of the haploid basidiospores, outside the basidium, follows directly
from plasmogamy and karyogamy. In the remaining fungi, plasmogamy need not
be followed immediately by karyogamy. Further, karyogamy need not be followed
immediately by meiosis. The haploid basidiospores form externally to the
basidium.