Answers
Activity 31.1 How Diverse Are the Fungi in Form and Function?
1. a. What is the basic body plan of most fungi?
The body of most fungi is composed of filamentous hyphae that can aggregate to form mats of mycelia (singular, mycelium) below ground or fruiting bodies that often appear above ground.
b. Which fungi do not share this basic body plan?
The yeasts are unicellular.
2. Fungi may be said to have both plantlike and animal-like characteristics. What plantlike characteristics do fungi have? What animal-like characteristics?
Like plants, the cells of fungi are surrounded by cell walls. Also, like many lower plants, they produce haploid spores as a means of reproduction and dispersal. However, the cell walls of fungi are composed of chitin (a substance found in some animal phyla) rather than cellulose. In addition, fungi are heterotrophic (like animals) rather than phototrophic.
3.
a. Into what four major phyla (or divisions) is the kingdom Fungi divided? / b. On what basis are these divisions made?Phylum Chytridiomycota / The chytridomycota are primarily aquatic, and unlike other fungi, their zoospores have flagella.
Phylum Zygomycota / The zygomycota produce resistant structures (zoosporangia) during reproduction.
Phylum Ascomycota / The ascomycota produce sexual spores in saclike asci (singular, ascus).
Phylum Basidiomycota / The basiodiomycota produce sexual spores in structures called basidia (singular, basidium).
4. Is it more correct to describe a mushroom as haploid or diploid? Explain.
The mushroom or fruiting body is for the most part a dikaryon; that is, the cells of the fruiting body contain two haploid nuclei. The dikaryon and fruiting body are the result
of the fusion of haploid mycelia of opposite mating types.
5. If you did not know that fungi were primarily terrestrial organisms, what structures or features of the organisms would suggest that they were terrestrial?
With the exception of the chytrids, the fungi produce spores. The spores are resistant
to desiccation and can be easily distributed by air currents.
6. a. In what ways are fungi important in the ecosystem?
Fungi are key decomposers in the ecosystem. As such, they are key recyclers of carbon compounds in the ecosystem.
b. In what ways are fungi important to humans?
On the negative side, many fungi are pathogens on humans, other animals, or crops.
On the positive side, fungi like yeast are important in the cheese-making, baking, and brewing industries. They are also the source of a wide range of antibiotics.
7. Lichens are symbiotic associations of a fungus, usually an ascomycete, and an alga, usually a green algal species or a cyanobacterial species. Lichens can often survive in harsh natural environments.
a. To what environmental conditions are lichens well adapted?
Lichens can be found in many environments, but the best-known lichen species are recognized for their ability to survive in extreme environments. For example, some species are capable of tolerating severe cold and can survive in the tundra. Others are capable of withstanding desiccation and can survive in very dry climates.
b. What makes them so well adapted to these conditions?
Neither the algae nor the fungus by itself appears able to withstand the severe conditions they can survive when combined as a lichen. In their symbiotic relationship as a lichen species, the alga produces food via photosynthesis and provides some of this to the fungus. The fungus, on the other hand, provides the alga with water and minerals as well as protection from intense sunlight.