Fungal Structures and Relationships
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Questions and Answers

What is true about coenocytic fungi?

  • They have specialized hyphae to capture prey.
  • They have a continuous cytoplasmic mass with hundreds or thousands of nuclei. (correct)
  • They have mycorrhizal relationships with plants.
  • They have hyphae divided into cells by septa.

    • Most fungi have specialized hyphae to capture prey.

    False

    What is the function of mycorrhizal fungi in relation to plants?

    Deliver phosphate ions and minerals to plants.

    The body of fungi is made up of a _______________________, which is an interwoven mass of hyphae.

    <p>mycelium</p> Signup and view all the answers

    Match the type of mycorrhizal fungi with its characteristic.

    <p>Ectomycorrhizal fungi = Do not penetrate root cells Arbuscular mycorrhizal fungi = Penetrate root cells</p> Signup and view all the answers

    Which of the following statements about mycorrhizae is FALSE?

    <p>They are in a commensalistic relationship with plants.</p> Signup and view all the answers

    The presence of mitochondria is a unique feature that helps identify a fungus.

    <p>False</p> Signup and view all the answers

    What is the unique feature that helps identify a fungus among single-celled organisms?

    <p>Presence of chitinous cell walls</p> Signup and view all the answers

    What is the normal state of fungal nuclei?

    <p>Haploid</p> Signup and view all the answers

    Fungi use sexual signaling molecules called enzymes to communicate their mating type.

    <p>False</p> Signup and view all the answers

    What is the process called when haploid nuclei from each parent do not fuse right away and coexist in the mycelium?

    <p>Heterokaryon</p> Signup and view all the answers

    The paired processes of karyogamy and ______________ produce genetic variation.

    <p>meiosis</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Plasmogamy = Union of cytoplasm from two parent mycelia Karyogamy = Fusion of haploid nuclei Heterokaryon = Coexistence of haploid nuclei from each parent in the mycelium</p> Signup and view all the answers

    How can you tell whether fungal offspring were produced by asexual reproduction?

    <p>Analyze the DNA via gel electrophoresis to determine whether it is genetically identical to the parental DNA</p> Signup and view all the answers

    Fungi can only reproduce sexually.

    <p>False</p> Signup and view all the answers

    What is the process called when haploid nuclei pair off two to a cell in some fungi?

    <p>Dikaryotic</p> Signup and view all the answers

    What is the characteristic of conidia formation?

    <p>Produced asexually at the tips of specialized hyphae called conidiophores</p> Signup and view all the answers

    Neurospora crassa is a model organism with a poorly studied genome.

    <p>False</p> Signup and view all the answers

    What is the name of the structure that defines the phylum Basidiomycota?

    <p>basidium</p> Signup and view all the answers

    Basidiomycetes are also known as _______________________ fungi.

    <p>club</p> Signup and view all the answers

    Match the following fungi with their characteristics:

    <p>Basidiomycota = includes mushrooms and puffballs Chytridiomycota = aquatic and flagellated Zygomycota = forms zygospores Ascomycota = forms ascospores</p> Signup and view all the answers

    What is the function of fungi in the ecosystem?

    <p>Decomposition, recycling of chemical elements, and bioremediation</p> Signup and view all the answers

    What does the diameter of a fairy ring indicate?

    <p>The diameter of the fairy ring indicates the age of the fungus.</p> Signup and view all the answers

    What is unique about the spores of Chytridiomycota?

    <p>They are flagellated</p> Signup and view all the answers

    Zygomycetes are commonly called sac fungi.

    <p>False</p> Signup and view all the answers

    What is the function of zygosporangia?

    <p>They are the site of karyogamy and then meiosis.</p> Signup and view all the answers

    Glomeromycetes form ____________________ mycorrhizae.

    <p>arbuscular</p> Signup and view all the answers

    What is the name of the fungal group that includes fast-growing molds, parasites, and commensal symbionts?

    <p>Zygomycota</p> Signup and view all the answers

    All fungal groups mentioned are found in terrestrial habitats.

    <p>True</p> Signup and view all the answers

    Match the following fungal groups with their characteristic features:

    <p>Chytridiomycota = Flagellated spores Zygomycota = Zygosporangia Glomeromycota = Arbuscular mycorrhizae Ascomycota = Saclike asci</p> Signup and view all the answers

    What is the name of the fungal group that includes plant pathogens, decomposers, and symbionts?

    <p>Ascomycota</p> Signup and view all the answers

    What is a characteristic of a lichen?

    <p>A symbiotic association between a photosynthetic microorganism and a fungus</p> Signup and view all the answers

    Mycorrhizae are important in natural ecosystems and agriculture.

    <p>True</p> Signup and view all the answers

    What do endophytes make to deter herbivores and defend against pathogens?

    <p>toxins</p> Signup and view all the answers

    Lichens are sensitive to _______________________, and their death can be a warning that air quality is deteriorating.

    <p>pollution</p> Signup and view all the answers

    Match the following types of fungi with their corresponding characteristics.

    <p>Ascomycete = amount of antibiotic produced Zygomycete = extent of infection with a protist Basidiomycete = age of the fungus</p> Signup and view all the answers

    What is the role of fungi in fungus-animal mutualism?

    <p>To break down plant material in the guts of grazing mammals</p> Signup and view all the answers

    Fungi in lichens can only reproduce sexually.

    <p>False</p> Signup and view all the answers

    What is the function of soredia in lichen reproduction?

    <p>asexual reproduction (small clusters of hyphae with embedded algae)</p> Signup and view all the answers

    What is the estimated number of fungi species believed to exist?

    <p>1.5 million</p> Signup and view all the answers

    Fungi are autotrophic organisms.

    <p>False</p> Signup and view all the answers

    What is the function of fungi in decomposition?

    <p>Fungi contribute to the decomposition of organic matter.</p> Signup and view all the answers

    The cell walls of fungi are made of _______________________.

    <p>chitin</p> Signup and view all the answers

    What type of relationship do mutualist fungi form with their host?

    <p>win-win</p> Signup and view all the answers

    Match the type of fungal lifestyle with its description:

    <p>Decomposer = Breaks down organic matter Parasite = Benefits from the host at the expense of the host Mutualist = Provides benefits to both the fungus and the host</p> Signup and view all the answers

    Fungi absorb nutrients through their plasma membranes.

    <p>True</p> Signup and view all the answers

    What is the name of the body of a fungus?

    <p>mycelium</p> Signup and view all the answers

    What is the term for the union of the cytoplasm of two different hyphae in fungi?

    <p>plasmogamy</p> Signup and view all the answers

    What is the result of karyogamy in fungi?

    <p>Diploid zygote</p> Signup and view all the answers

    Fungi can only engage in sexual reproduction.

    <p>False</p> Signup and view all the answers

    Fungi use chemical signals called _______________ to attract a mate.

    <p>pheromones</p> Signup and view all the answers

    Match the following types of reproduction with their characteristics:

    <p>Sexual reproduction = Involves the fusion of two nuclei Asexual reproduction = Involves the production of spore-modifying structures</p> Signup and view all the answers

    What is the term for the stage in the lifecycle of a fungus where the nuclei from each hypha come close together but do not fuse immediately?

    <p>dikaryon</p> Signup and view all the answers

    Fungi can only reproduce asexually when conditions are favorable and resources are abundant.

    <p>True</p> Signup and view all the answers

    What is an example of asexual reproduction in fungi?

    <p>All of the above</p> Signup and view all the answers

    The fungus Rhizopus nigricans has distinct sexes.

    <p>False</p> Signup and view all the answers

    What is the purpose of the thick wall of the zygosporangium?

    <p>To protect the diploid zygote from harsh environments</p> Signup and view all the answers

    What is the result of meiosis in the zygosporangium?

    <p>Haploid nuclei</p> Signup and view all the answers

    The fusion of gametangia results in the formation of a _______________ zygote.

    <p>diploid</p> Signup and view all the answers

    What is the function of sporangia in the life cycle of Rhizopus nigricans?

    <p>To release haploid spores</p> Signup and view all the answers

    Match the following structures with their functions in the life cycle of Rhizopus nigricans:

    <p>Sporangia = Release haploid spores Gametangia = Fuse to form a zygote Zygosporangium = Protect the diploid zygote Hyphae = Absorb nutrients</p> Signup and view all the answers

    Rhizopus nigricans can only reproduce asexually.

    <p>False</p> Signup and view all the answers

    The growth of side branches in Rhizopus nigricans is triggered by the release of _______________.

    <p>pheromones</p> Signup and view all the answers

    What is the characteristic reproductive structure of the phylum Basidiomycota?

    <p>Basidium</p> Signup and view all the answers

    The gills on the underside of a mushroom are used for respiration.

    <p>False</p> Signup and view all the answers

    What is the function of basidia in the life cycle of Basidiomycota?

    <p>Basidia produce four basidiospores through meiosis.</p> Signup and view all the answers

    The life cycle of Basidiomycota begins with ______________, which fuse to form a diploid basidiocarp.

    <p>hyphae</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Basidia = Club-like reproductive structure that produces basidiospores Basidiospores = Haploid spores produced by basidia through meiosis Basidiocarp = The reproductive structure of Basidiomycota, which includes the mushroom cap and gills</p> Signup and view all the answers

    Basidiomycota are not an important part of the human diet.

    <p>False</p> Signup and view all the answers

    What is the name of the reproductive structure of Ascomycota?

    <p>Ascocarp</p> Signup and view all the answers

    Each ascus contains exactly 4 ascospores.

    <p>False</p> Signup and view all the answers

    What is the process of cell division that occurs in the ascus to produce ascospores?

    <p>Meiosis</p> Signup and view all the answers

    Ascospores disperse and land in different locations, and if conditions are favorable, an ascospore will _____________ and grow into hyphae.

    <p>germinate</p> Signup and view all the answers

    Match the following terms with their descriptions:

    <p>Ascocarp = The reproductive structure of Ascomycota Ascus = The structure within the ascocarp where meiosis occurs and ascospores are produced Ascospores = The spores produced by Ascomycota through meiosis Meiosis = The process of cell division that occurs in the ascus to produce ascospores</p> Signup and view all the answers

    Hyphae of opposite mating types can fuse to form a new ascocarp, starting the cycle again.

    <p>True</p> Signup and view all the answers

    Study Notes

    Fungal Structure and Hyphae

    • Most fungi have hyphae divided into cells by septa, with pores allowing cell-to-cell movement of organelles
    • Coenocytic fungi lack septa and have a continuous cytoplasmic mass with hundreds or thousands of nuclei
    • Specialized hyphae can be found in some fungi, such as those that capture prey or penetrate the tissues of their host (haustoria)
    • Mycorrhizal fungi deliver phosphate ions and minerals to plants and can be classified into ectomycorrhizal and arbuscular mycorrhizal fungi

    Life Cycles

    • Fungal nuclei are normally haploid, with the exception of transient diploid stages formed during the sexual life cycle
    • Sexual reproduction requires the fusion of hyphae from different mating types, which communicate through pheromones
    • Plasmogamy is the union of cytoplasm from two parent mycelia, and karyogamy is the fusion of haploid nuclei
    • The diploid phase is short-lived and undergoes meiosis, producing haploid spores
    • Asexual reproduction occurs through mitosis, producing haploid spores in molds and budding in yeasts

    Fungal Diversity

    • Chytridiomycota: found in freshwater and terrestrial habitats, they can be decomposers, parasites, or mutualists, and have flagellated spores called zoospores
    • Zygomycota: exhibits great diversity of life histories, includes fast-growing molds, parasites, and commensal symbionts, and has coenocytic hyphae
    • Glomeromycota: forms arbuscular mycorrhizae and was previously classified as Zygomycota
    • Ascomycota: produces sexual spores in sac-like asci, includes plant pathogens, decomposers, and symbionts, and can reproduce asexually through conidia
    • Basidiomycota: includes mushrooms, puffballs, and shelf fungi, mycorrhizae, and plant parasites, and has a club-like structure called a basidium

    Ecological Roles of Fungi

    • Decomposition: fungi are efficient decomposers of organic material, including cellulose and lignin, and perform essential recycling of chemical elements
    • Fungus-plant mutualism: mycorrhizae are important in natural ecosystems and agriculture, and endophytes can make toxins that deter herbivores and defend against pathogens
    • Fungus-animal mutualism: some fungi help break down plant material in the guts of grazing mammals, and some ants use fungi in "farms"
    • Lichens: symbiotic associations between photosynthetic microorganisms and fungi, important pioneers on new rock and soil surfaces, and sensitive to pollution

    General Characteristics of Fungi

    • Fungi are eukaryotes with cells having a nucleus and membranous organelles.
    • There are approximately 100,000 named and described species of fungi, but estimates suggest up to 1.5 million different species exist.

    Nutrition

    • Fungi are heterotrophs, obtaining nutrients by breaking down and absorbing surrounding organic matter.
    • Fungi absorb nutrients through their plasma membranes rather than consuming food like animals.
    • Digestion occurs both outside and inside fungal cells.

    Lifestyles

    • Decomposer fungi contribute to the decomposition of organic matter.
    • Parasitic fungi benefit from their hosts at the expense of the hosts.
    • Mutualist fungi engage in win-win relationships, providing benefits to both the fungus and the host.

    Body Structure

    • A fungus's body is called a mycelium, composed of thin, thread-like filaments called hyphae.
    • The mycelium is typically hidden from view, with only the reproductive structures visible.
    • Fungal cell walls are made of chitin, a unique characteristic.

    Cell Characteristics

    • Fungal cells can have partial divisions between their nuclei, separated by septa.
    • Septate fungi have dividers between their cells, while coenocytic fungi lack these dividers.

    Specialized Forms

    • Some fungi have modified hyphae that can trap prey, such as nematode worms.
    • Others can form associations with plants, penetrating their cell walls and forming mycorrhizal relationships.

    Mycorrhizal Relationships

    • Mycorrhizae are relationships between fungi and plant roots.
    • There are two types of mycorrhizae: ectomycorrhizae and endomycorrhizae.
    • Ectomycorrhizae form relationships outside plant cell walls, while endomycorrhizae penetrate the cell walls.
    • Both types of mycorrhizae are mutualistic, with the fungus providing water and nutrients in exchange for organic compounds from the plant.

    Introduction to Fungi

    • The golden mushroom in Oregon is one of the oldest and largest living organisms on earth.

    Sexual Reproduction in Fungi

    • Fungi use pheromones to attract a mate, which are chemical signals released to the outside environment.
    • When two fungi mate, their hyphae fuse, resulting in plasmogamy, the union of the cytoplasm of two different hyphae.
    • After plasmogamy, the nuclei from each hypha come close together but do not fuse immediately, forming a dikaryon.
    • The dikaryotic stage can last from hours to centuries.
    • Eventually, the two nuclei fuse, resulting in karyogamy, the union of two nuclei from different hyphae.
    • The result of karyogamy is a diploid zygote, the only diploid stage in the lifecycle of a fungus.

    Life Cycle of Fungi

    • The zygote undergoes meiosis, reducing the number of chromosomes in half, resulting in haploid spores.
    • Haploid spores can engage in either sexual or asexual reproduction.

    Asexual Reproduction in Fungi

    • Examples of asexual reproduction in fungi include molds, such as penicillin.
    • Asexual reproduction occurs when conditions are favorable, and resources are abundant.
    • Asexual reproduction can result in the production of large amounts of spores.
    • Budding is another form of asexual reproduction, seen in yeast cells, which are single-celled organisms.
    • Budding involves the formation of a new cell as an outgrowth from a mature yeast cell, making yeast cells temporarily multicellular.

    Life Cycle of Black Bread Mold (Rhizopus Nigricans)

    • Black bread mold has both asexual and sexual reproductive phases.

    Asexual Reproduction

    • Sporangia are produced through asexual reproduction, containing haploid spores.
    • Sporangia break open, releasing haploid spores that disperse through the air to find food sources.
    • A spore germinates by sending an elongated hypha into a food source, absorbing nutrients.
    • The new haploid fungus can produce more sporangia, initiating additional asexual reproduction cycles.

    Sexual Reproduction

    • The fungus has two mating types (plus and minus) but lacks distinct sexes.
    • Adjacent hyphae of the two mating types release pheromones, triggering side branch growth.
    • Nuclei stream into side branches, and a cross wall forms, isolating haploid nuclei in gametangia.
    • Gametangia fuse, and nuclei pair up, eventually fusing to form a diploid zygote.

    Zygosporangium Formation

    • The diploid zygote develops into a zygosporangium, with a thick, protective wall, allowing dormancy for months.
    • Diploid nuclei within the zygosporangium undergo meiosis, producing haploid nuclei.
    • Haploid nuclei are incorporated into spores when the zygosporangium sprouts.
    • Spores disperse and germinate, forming the next generation of haploid hyphae.

    Phylum Basidiomycota

    • Characterized by a reproductive structure called a basidium or basidia, commonly known as club fungi.
    • Most mushrooms that are seen and eaten belong to this phylum.

    Gills

    • The underside of a mushroom has many gills, which are respiratory structures that resemble fish gills but are not used for respiration.
    • Gills are where many reproductive structures are located, including basidia and spores.

    Life Cycle

    • Begins with haploid hyphae that fuse to form a diploid basidiocarp, the reproductive structure.
    • Within the basidiocarp, basidia produce four haploid basidiospores through meiosis.
    • Basidiospores grow into haploid hyphae, repeating the cycle.

    Key Terms

    • Basidia: Club-like reproductive structures that produce haploid basidiospores through meiosis.
    • Basidiospores: Haploid spores produced by basidia through meiosis.
    • Basidiocarp: The reproductive structure of Basidiomycota, including the mushroom cap and gills.

    Importance

    • Basidiomycota play a crucial role in the human diet, with many edible mushrooms belonging to this phylum.
    • Their life cycle is similar to other fungal phyla, with key differences in terminology.

    Phylum Ascomycota

    • Also known as sac fungi, characterized by holding spores in a structure called an ascus
    • Examples include truffles, morel mushrooms, and cup fungi

    Life Cycle

    • Hyphae grow in substrate (dirt, log, etc.) and are haploid with positive or negative mating types
    • Fusion of hyphae with opposite mating types forms an ascocarp, the reproductive structure
    • Ascocarp grows above ground and is visible to the naked eye

    Reproductive Cycle

    • Meiosis occurs in specialized cells within the ascocarp, producing ascospores
    • Each ascus contains exactly 8 haploid ascospores resulting from meiosis
    • Ascospores are released into the environment when the ascus bursts open

    Dispersal and Germination

    • Ascospores disperse and land in different locations, germinating if conditions are favorable
    • Germinated ascospores grow into hyphae, which can fuse with opposite mating types to form a new ascocarp

    Key Terms

    • Ascocarp: reproductive structure of Ascomycota, grows above ground and is visible
    • Ascus: structure within the ascocarp where meiosis produces ascospores
    • Ascospores: haploid spores produced through meiosis in the ascus
    • Meiosis: process of cell division in the ascus that produces ascospores

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