A list of phyla belonging to the kingdom Fungi is provided: Zygomycota, Ascomycota, Basidiomycota. An organism is found that has divided hyphae and that produces spores by sexual reproduction on a club-shaped structure. Which phylum of fungi is it most likely to belong to?
The question gives us some characteristics of a fungus and asks us to determine its phylum. So put on your detective hat as we do a little fungal investigation.
Let’s start by making a table so we can organize the provided phyla and the clues about our mystery fungus. Our first clue is that the fungus has divided hyphae. So let’s call the first column of clues hyphae structure. Hyphae are the tiny branching filaments found in nearly all fungal species. If we zoom in for a closer look, we can see that some hyphae are undivided, meaning there is no separation between the nuclei of the cells. Other hyphae are divided by walls between the cells called septa. Members of Zygomycota have undivided hyphae, so we can rule this phylum out. Members of Ascomycota and Basidiomycota have divided hyphae, so both of these phyla are still possibilities.
Our next clue is that the fungus produces spores by sexual reproduction. So let’s call our next column of clues spore production. Spores are the haploid cells that allow fungi to reproduce. Most fungi can produce spores asexually through a simple cycle of mitosis and germination to produce genetically identical hyphae. Nearly all fungal species can also produce spores through a sexual cycle. This typically occurs when cells from two different types of hyphae fuse their cytoplasm and nuclei to create a diploid zygote. This zygote will undergo meiosis to produce spores, which will germinate to produce genetically unique hyphae. Members of all three phyla can produce spores sexually, so we can’t identify our mystery fungus yet.
Let’s move on to our final clue. It tells us that the fungus produces spores on a club-shaped structure. So let’s call the last column of our table site of spore production. Members of Zygomycota produce spores within a structure called a sporangium. Sporangia look more like tiny lollipops than clubs, which supports our earlier decision to rule out Zygomycota. Members of Ascomycota produce spores in a structure called an ascus. An ascus looks more like a small sack than a club. But let’s check our last phylum before ruling out Ascomycota. Species belonging to Basidiomycota produce spores at the end of a structure called a basidium. Basidia are club shaped, so we can now confirm that our mystery fungus belongs to the phylum Basidiomycota. Mystery solved!