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Fungi I - Evolution and Diversity, Phyla Chytridiomycota and Zygomycota

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Members of the kingdom Fungi produce spores. Although they are mostly nonmotile (some members of the Chytridiomycota produce flagellated spores), spores (produced by the thousands or millions) can be dispersed by water and/or wind great distances to another available substrate or host. Spores are an important taxonomic character and, as expected, come in an array of shapes and sizes. Spores can be mitotically or meiotically produced, affording the organism flexibility to reproduce and proliferate over a variety of environmental conditions where sexual recombination may not be feasible.

Fungi play many roles in the biosphere. As you have already learned, they are important decomposers as well as plant and human pathogens. They also engage in extremely important symbiotic relationships with plants and algae. Mycorrhizae (Fig. 5) are an intimate association (symbiosis) between plant roots and fungal hyphae. The vast majority are mutualistic, with the plant or tree benefiting with increased water and nutrient uptake and the fungus obtaining carbon from the roots.  All of the members of the glomeromycetes are participants in a mycorrhizal relationship with a plant. Symbioses with lichens are also common. Specific fungal species (usually Ascomycetes) grow in concert with green algae, or occasionally a cyanobacterium. The fungus gains carbon from the photosynthetic partner, and in turn it provides moisture in a controlled parasitic relationship. Technically, it's not a mutualistic relationship since the alga can live on its own and is consumed by the fungus; however, it is to its photosynthetic partner.This is a unique relationship since lichens can grow in extremely harsh climates (e.g., the arctic tundra and bare rocks) in which the algae or bacteria might not normally be able to survive individually.  the The Cordyceps genus of fungi exhibits a novel method of entomopathogenesis, hijacking the nervous systems of certain insects.  Watch this video to see the fungus in action. What effect do they fungi have on they ants they parasitize?  How does these behaviors help the fungus?


Figure 5. Mycorrhizal root tips. (Click to enlarge) (Wikipedia Commons)