Flagellated spores — Which division of fungi characteristically produces uniflagellated (single-flagellum) zoospores?

Introduction / Context:
Motile spores are unusual among true fungi. Knowing which group retains a flagellated life stage helps place chytrids at the base of the fungal lineage and distinguish them from fungal-like organisms such as oomycetes.

Given Data / Assumptions:

• Zoospores are flagellated, swimming spores.
• Chytrids occur in aquatic and soil habitats and can be parasitic or saprobic.
• Other major fungal divisions typically form non-motile spores.

Concept / Approach:
Chytridiomycota produce uniflagellated, posteriorly inserted whiplash zoospores. Oomycota (water molds) produce biflagellate zoospores but are stramenopiles, not true fungi. Ascomycota and the former Zygomycota lack motile spores.

Step-by-Step Solution:

Verification / Alternative check:
Electron microscopy shows the posterior whiplash flagellum typical of chytrid zoospores; phylogeny places chytrids as early-diverging fungi.

Why Other Options Are Wrong:

• Ascomycota/Zygomycota: spores are non-motile.
• Oomycota: biflagellate zoospores, but not in the fungal kingdom.

Common Pitfalls:
Equating water molds with true fungi; despite similar growth forms, they belong to a different lineage.

Final Answer:
Chytridiomycota