BSC-116-001 Chapter 31

Spore

(1) In the life cycle of a plant or alga undergoing alternation of generations, a haploid cell produced in the sporophyte by meiosis. A spore can divide by mitosis to develop into a multicellular haploid individual , the gametophyte, without fusing with another cell. (2) In fungi, a haploid cell, produced sexually or asexually, that produces mycelium after germination.

Heterokaryon

A fungal mycelium that contains two or more haploid nuclei per cell.

Conidia

A haploid spore produced at the tip of the hypha in ascomycetes during asexual reproduction.

Chytrid

A member of the fungal phylum Chytridiomycota, mostly aquatic fungi with flagellated zoospores that represent an early-diverging fungal lineage.

Zygomycete

A member of the fungal phylum Zygomycota, characterized by the formation of a study structure called a zygosporangium during sexual reproduction. (black bread mold)

Mycorrhizae

A mutualistic association of plant roots and fungus.

Chitin

A structural polysaccharide consisting of amino sugar monomers, found in many fungal cell walls and the exoskeletons of all anthropods.

Ectomycorrhizal fungus

A symbiotic fungus that forms a sheath of hyphae over the surface of plant roots and also grows into extracellular spaces of the root cortex.

Arbuscular mycorrhizal fungi

A symbiotic fungus whose hyphae grow through the cell wall of plant roots and extend into the root cell.

Select the correct statement(s) about the origin of fungi. Select all that apply. A. Multicellularity probably arose independently in fungi and animals. B. Fungi evolved after the first plants colonized land. C. Fungi are more closely related to plants than to animals.

A. Multicellularity probably arose independently in fungi and animals. DNA sequence data indicate that fungi are more closely related to several groups of unicellular protists than they are to animals, and that animals are more closely related to a different group of unicellular protists than they are to fungi. Therefore, multicellularity probably arose independently in fungi and animals. Read about the origin of fungi.

True or false? Most of the cells in a mushroom contain haploid nuclei. A. True B. False

A. True A mushroom consists mainly of hyphae that are heterokaryotic, which means they have two distinct haploid nuclei per cell; these nuclei may fuse in specialized cells called basidia and become diploid in preparation for meiosis and spore production.

Fungi obtain nutrients through _____. A. absorption B. ingestion C. chemosynthesis D. endocytosis E. photosynthesis

A. absorption Fungi are heterotrophs that acquire their nutrients by absorbing small molecules from the surrounding medium.

The closest relatives of fungi are thought to be the A. animals B. vascular plants C. mosses D. slime molds

A. animals

Karyogamy produces a _____. A. diploid zygote B. haploid zygote C. spores D. mycelium E. hypha

A. diploid zygote Karyogamy is the fusion of nuclei.

The diploid phase of the life cycle is shortest in which of the following? A. fungus B. angiosperm C. moss D. gymnosperm E. fern

A. fungus Most fungi are haploid except for a very brief diploid stage that is seen only when a fungus reproduces sexually.

The body of most fungi consists of threadlike _____, which form a network called a _____. A. hyphae ... mycelium B. sporangia ... dikaryon C. mycelia ... dikaryon D. mycelia ... hypha E. hyphae ... chytrid

A. hyphae ... mycelium Hyphae form a network called a mycelium.

Which of these contains two haploid nuclei? A. the heterokaryotic stage of the fungal life cycle B. zygote C. spore-producing structures D. mycelium E. hypha

A. the heterokaryotic stage of the fungal life cycle The heterokaryotic stage is produced by plasmogamy.

The following statements describe something about the body structures or functions of fungi. Identify those statements that are correct. Select all that apply. A. Mycelia are made up of small-diameter hyphae that form an interwoven mass, providing more surface area for nutrient absorption. B. Cellulose gives rigidity and strength to the cell walls of fungi. C. Some fungi secrete digestive enzymes into the environment and then absorb the digested nutrients. D. Some fungi can grow as either filamentous or single-celled forms. E. All fungi are heterotrophs; some species live as decomposers and others as symbionts. F. Nutrients can flow through the entire mycelium in fungi with coenocytic hyphae, but not in fungi with septate hyphae.

A., C., D., E. All fungi are heterotrophs. Most obtain carbon compounds by decomposing organic matter, while others live in a symbiotic association with other organisms. The feeding structure of a multicellular fungus is the mycelium, which consists of numerous small-diameter filaments, or hyphae. Nutrients absorbed by the hyphae can flow throughout the mycelium in both coenocytic hyphae and septate hyphae.

True or false? In most fungi, fertilization is complete after the cells fuse together. A. True B. False

B. False In most fungi, fertilization is a two-step process consisting of the fusion of cells and then the fusion of nuclei in the fused cells.

Almost all of the members of this phylum form arbuscular mycorrhizae in a mutualistic partnership with plants. A. Chytridiomycota B. Glomeromycota C. Zygomycota D. Basidiomycota E. Ascomycota

B. Glomeromycota Nearly all glomeromycetes form arbuscular mycorrhizae.

Which of the following events occurs first in the development of a spore into a mature mushroom? A. The mycelium forms. B. Hyphae are produced by mitosis. C. A heterokaryotic mycelium forms. D. Haploid nuclei fuse to form a diploid nucleus.

B. Hyphae are produced by mitosis. The spore undergoes mitosis to produce hyphae, which then form a filamentous network called a mycelium.

All fungi are A. symbiotic B. heterotrophic C. flagellated D. decomposers

B. heterotrophic

Cup fungi are in the phylum _____. A. Zygomycota B. Chytridomycota C. Ascomycota D. Chordata E. Basidiomycota

C. Ascomycota Cup fungi are a type of sac fungus.

Which of the following is a difference between plants and fungi? A. Fungi have cell walls. B. Plants produce spores. C. Fungi are heterotrophic, and plants are autotrophic. D. Fungi are strictly asexual, and plants undergo sexual reproduction. E. Plants have diploid and haploid phases, and fungi have only haploid stages.

C. Fungi are heterotrophic, and plants are autotrophic. Fungi are heterotrophic and absorb their nutrients, and plants are photosynthetic.

Which structure is not directly involved in the reproduction of at least one major group of fungi? A. Basidium B. Asci C. Mycelium D. Motile spores

C. Mycelium A mycelium is a network of filaments that forms the body of a fungus.

Which structure allows the growing mushroom to nourish itself? A. Spore B. Basidia C. Mycelium D. Gills

C. Mycelium The mycelium is a mass of filaments with a high surface-area-to-volume ratio, which allows for efficient nutrient absorption.

Which term describes the fusion of cytoplasm from two individuals? A. Heterokaryotic B. Karyogamy C. Plasmogamy D. Spore

C. Plasmogamy Plasmogamy is the fusion of cytoplasm from different individuals.

In fungi, haploid hyphae fuse to produce dikaryotic and then diploid nuclei, only to restore the haploid condition by meiosis before the growth of new hyphae. What is the significance of a transient diploid state in fungi? A. All organisms must reproduce sexually at some point in their life cycle. B. The diploid state is more advanced than the haploid state. C. These sexual processes generate genetic variation.

C. These sexual processes generate genetic variation. The sexual processes of karyogamy and meiosis generate extensive genetic variation, a prerequisite for natural selection.

Fungi produce _____ spores. A. dikaryotic B. heterokaryotic C. haploid D. diploid E. triploid

C. haploid Fungal spores are haploid.

Basidiomycete

Commonly called club fungus. The name comes from the club-like shape of the basidium. Sexual spores formed in the basidia, with basidocarps (fruiting bodies). Include mushrooms, puffballs, and shelf fungi.

Ascomycete

Commonly called sac fungus. The name comes from the saclike structure in which spores develop. They have fruiting bodies called assocarps. Include yeasts and multicellular fungi.

Where does meiosis occur in a mushroom? A. Spores B. Hyphae C. Mycelium D. Basidia

D. Basidia Basidia are specialized cells in the gills of a mushroom in which haploid nuclei fuse in preparation for meiosis.

The most important adaptive advantage associated with the filamentous nature of fungal mycelia is A. the ability to perform haustoria. B. the potential to inhabit almost all terrestrial habitats. C. the increased chance of contact between mating types. D. an extensive surface area well suited for invasive growth and absorptive nutrition.

D. an extensive surface area well suited for invasive growth and absorptive nutrition.

Which of the following cells or structures are associated with asexual reproduction in fungi? A. ascospores B. basidiospores C. zygosporangia D. conidiophores

D. conidiophores

An important example of interaction between fungi and certain other organisms is mycorrhizae, in which the fungal partners _____. A. sicken herbivores that attempt to feed on plants B. provide carbohydrates to the plant partner C. cause the decay of cellulose and lignin D. help plants take up nutrients and water E. control soil nematodes

D. help plants take up nutrients and water Mycorrhizae are mutualistic associations with the roots of plants, which enhance the absorption of nutrients.

What sexual processes in fungi generate genetic variation? A. diploidy and the heterokaryotic condition B. plasmogamy and meiosis C. haustoria and karyogamy D. karyogamy and meiosis E. budding and meiosis

D. karyogamy and meiosis During karyogamy, the haploid nuclei fuse, and meiosis produces genetic variation in several ways.

Fungi form mutualistic relationships with plants and animals. Which of the following is an example of such a relationship? A. Fungi help break down wood in the guts of termites. B. Fungi help break down plant material in the guts of grazing mammals. C. Endophytes in leaves produce toxins that deter herbivores. D. Fungi can help increase drought tolerance in plants E. All of the above.

E. All of the above. Fungi enter into these and many other mutualistic relationships with other organisms.

From the human perspective, which of the following kinds of fungi would be considered the least useful or beneficial? A. yeasts B. truffles C. mycorrhizal fungi D. decomposers E. rusts

E. rusts Rusts include destructive plant parasites.

Fungi of the phylum Ascomycota are recognized on the basis of their production of _____ during sexual reproduction. A. flagellated zoospores B. lichens C. a dikaryotic structure D. yeasts E. saclike structures

E. saclike structures The production of saclike structures during sexual reproduction is characteristic of the phylum Ascomycota.

Fungi

Heterotrophs that feed by absorption; produce spores through sexual or asexual life cycles; ancestor was a flagellated protist; play key roles in nutrient cycling, ecological interactions, and human welfare.

Pheromone

In animals and fungi, a small molecule is released into the environment that functions in communication between members of the same species.

Haustoria

In certain symbiotic fungi, a specialized hypha that can penetrate the tissues of host organisms.

Karyogamy

In fungi, the fusion of haploid nuclei contributed by two parents; occurs as one stage of sexual reproduction, preceded by plasmogamy.

Plasmogamy

In fungi, the fusion of the cytoplasm of cells from two individuals; occurs as one stage of sexual reproduction, followed later by karyogamy.

Zygosporangium

In zygomycete fungi, a sturdy multinucleate structure in which karyogamy and meiosis occur.

Mold

Informal term for a fungus that grows as a filamentous fungus, producing haploid spores by mitosis and forming visible mycelium.

Hyphae

One of many connected filaments that collectively make up the mycelium of a fungus.

Septa

One of the cross-walls that divide the fungal hypha into cells. Septa generally have large pores large enough to allow ribosomes, mitochondria, and even nuclei to flow from cell to cell.

Dikaryotic

Referring to a fungal mycelium with two haploid nuclei per cell, one from each parent.

Yeast

Single-Celled fungus. Yeasts reproduce asexually by binary fission or by the pinching of small buds off a parent cell. Many fungal species grow as yeasts and as a network of filaments; relatively few species grow only as yeasts.

Mycelium

The densely branched network of hyphae in a fungus.

Lichen

The mutualistic association between a fungus and a photosynthetic alga or cyanobacterium. Common with Ascomycetes and green algae.