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Chapter 25 Review
1 What is the significance of kingdom Fungi to the environment?
Fungi play a vital role in ecosystems. Without certain species of fungi serving as decomposers,
ecosystems would collapse. These decomposers break down dead organisms, leaves, feces, and organic
matter and recycle their chemical components back into the environment. In addition, many species of
plants depend upon mutualisticfungi to help their roots absorb minerals and water from the soil.
2 Where can chytrids be found?
Most of these minute fungi are unicellular and live in freshwater environments, moist environments, and
leaf litter as well as on animals, such as insects and amphibians.
3 What is the evolutionary significance of phylum Chytridiomycota?
They are the oldest known fungi in the fossil record.
4 Name and describe five typical ascomycetes.
The yeast Saccharomyces cerevisia, an ascomycete, plays important roles in the brewing industry and in
genetic research. Another yeast, Candida albicans, causes a variety of fungus infections, including oral
thrush and vaginal infections. Neurospora sp., a type of bread mold, has contributed to genetic studies.
True morels are common woodland ascomycetes featuring a convoluted cap. One of the most interesting
ascomycetes, Claviceps purpurea,grows on rye and similar plants.
5 Trace the generalized life cycle
of an ascomycete.
Conidia
Mature hypha (n)
Trichogyne
Antheridium
Ascogonium
Ascospores (n)
Ascogenous
hyphae (n+n)
8-celled stage
formation of
ascospores
8-nucleate
stage
4-nucleate
stage
Ascoma with
mature asci
Formation of ascogenous
hook (crozier)
Karyogamy
Meiosis
Mitosis Plasmogamy
Sexual cycle
Asexual cycle
25.10 Life cycle
of an ascomycete.
Figure
6 Provide an example of phylum Glomeromycota and its biological significance.
Mycorrhizae were important to the evolutionary success of terrestrial plants in conquering the land.
7 What are five typical basidiomycetes?
Five typical basidiomycetes are mushrooms, puffballs, stinkhorns, rusts, and smuts.
8 Trace the generalized life cycle of a basidiomycete.
Strain 2
Strain 1
Primary hyphae (n)
Germinating basidiospores
Basidiospores (n)
Sterigma
Sterigma
Basidium
Diploid basidium
Gills
Pileus (cap) (n+n)
Annulus
Stipe (stalk)
Volva
Secondary hyphae
(n+n)
Plasmogamy
Dikaryotic Stage
Diploid Stage
Karyogamy
Meiosis
Figure
25.20 Life cycle of a “typical” basidiomycete (mushroom).11
9 Draw and label a typical mushroom.
Sketches will vary, but make sure student includes
pileus (cap), stipe (stalk), gills, and annulus.
10 What are three important ascomycetes?
Aspergillus sp. is a genus of green mold that can cause deadly respiratory infections.
The best known ascomycete is Penicillium chrysogenum, formerly called Penicillium notatum. It is the
source of penicillin. Less friendly species of ascomycetes include Trichophyton sp., which causes
athlete’s foot, ringworm, jock itch, and small nonpigmented splotches of skin better known as Tinea
infections.
11 What is a lichen? Name and describe three types of lichens.
Lichens are symbionts consisting of green algae or cyanobacteria and, with the exception of a few
species, ascomycetes.
Algal cells or cyanobacteria are thought to provide food for both symbionts through photosynthesis,
and the ascomycete retains water and minerals, anchors the organism, and protects the algae. Three
basic types of lichens exist in nature:
1. Crustose lichens form brightly colored patches or crusts on rock or tree bark, without evident lower
surfaces.
2. Foliose lichens appear to have leaflike thalli that overlap, forming a scaly, lobed body. These lichens
frequently are found on tree bark and on human-made structures.
3. Fruticose lichens may appear shrub-like or hanging mosslike on trees. Their thalli are either highly
branched or cylindrical.