Fungal Structures and Relationships

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.

mycelium Signup and view all the answers

Match the type of mycorrhizal fungi with its characteristic.

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

Which of the following statements about mycorrhizae is FALSE?

They are in a commensalistic relationship with plants. Signup and view all the answers

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

False Signup and view all the answers

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

Presence of chitinous cell walls Signup and view all the answers

What is the normal state of fungal nuclei?

Haploid Signup and view all the answers

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

False 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?

Heterokaryon Signup and view all the answers

The paired processes of karyogamy and ______________ produce genetic variation.

meiosis Signup and view all the answers

Match the following terms with their descriptions:

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

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

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

Fungi can only reproduce sexually.

False Signup and view all the answers

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

Dikaryotic Signup and view all the answers

What is the characteristic of conidia formation?

Produced asexually at the tips of specialized hyphae called conidiophores Signup and view all the answers

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

False Signup and view all the answers

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

basidium Signup and view all the answers

Basidiomycetes are also known as _______________________ fungi.

club Signup and view all the answers

Match the following fungi with their characteristics:

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

What is the function of fungi in the ecosystem?

Decomposition, recycling of chemical elements, and bioremediation Signup and view all the answers

What does the diameter of a fairy ring indicate?

The diameter of the fairy ring indicates the age of the fungus. Signup and view all the answers

What is unique about the spores of Chytridiomycota?

They are flagellated Signup and view all the answers

Zygomycetes are commonly called sac fungi.

False Signup and view all the answers

What is the function of zygosporangia?

They are the site of karyogamy and then meiosis. Signup and view all the answers

Glomeromycetes form ____________________ mycorrhizae.

arbuscular Signup and view all the answers

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

Zygomycota Signup and view all the answers

All fungal groups mentioned are found in terrestrial habitats.

True Signup and view all the answers

Match the following fungal groups with their characteristic features:

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

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

Ascomycota Signup and view all the answers

What is a characteristic of a lichen?

A symbiotic association between a photosynthetic microorganism and a fungus Signup and view all the answers

Mycorrhizae are important in natural ecosystems and agriculture.

True Signup and view all the answers

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

toxins Signup and view all the answers

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

pollution Signup and view all the answers

Match the following types of fungi with their corresponding characteristics.

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

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

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

Fungi in lichens can only reproduce sexually.

False Signup and view all the answers

What is the function of soredia in lichen reproduction?

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

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

1.5 million Signup and view all the answers

Fungi are autotrophic organisms.

False Signup and view all the answers

What is the function of fungi in decomposition?

Fungi contribute to the decomposition of organic matter. Signup and view all the answers

The cell walls of fungi are made of _______________________.

chitin Signup and view all the answers

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

win-win Signup and view all the answers

Match the type of fungal lifestyle with its description:

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 Signup and view all the answers

Fungi absorb nutrients through their plasma membranes.

True Signup and view all the answers

What is the name of the body of a fungus?

mycelium Signup and view all the answers

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

plasmogamy Signup and view all the answers

What is the result of karyogamy in fungi?

Diploid zygote Signup and view all the answers

Fungi can only engage in sexual reproduction.

False Signup and view all the answers

Fungi use chemical signals called _______________ to attract a mate.

pheromones Signup and view all the answers

Match the following types of reproduction with their characteristics:

Sexual reproduction = Involves the fusion of two nuclei Asexual reproduction = Involves the production of spore-modifying structures 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?

dikaryon Signup and view all the answers

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

True Signup and view all the answers

What is an example of asexual reproduction in fungi?

All of the above Signup and view all the answers

The fungus Rhizopus nigricans has distinct sexes.

False Signup and view all the answers

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

To protect the diploid zygote from harsh environments Signup and view all the answers

What is the result of meiosis in the zygosporangium?

Haploid nuclei Signup and view all the answers

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

diploid Signup and view all the answers

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

To release haploid spores Signup and view all the answers

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

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

Rhizopus nigricans can only reproduce asexually.

False Signup and view all the answers

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

pheromones Signup and view all the answers

What is the characteristic reproductive structure of the phylum Basidiomycota?

Basidium Signup and view all the answers

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

False Signup and view all the answers

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

Basidia produce four basidiospores through meiosis. Signup and view all the answers

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

hyphae Signup and view all the answers

Match the following terms with their descriptions:

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 Signup and view all the answers

Basidiomycota are not an important part of the human diet.

False Signup and view all the answers

What is the name of the reproductive structure of Ascomycota?

Ascocarp Signup and view all the answers

Each ascus contains exactly 4 ascospores.

False Signup and view all the answers

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

Meiosis 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.

germinate Signup and view all the answers

Match the following terms with their descriptions:

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 Signup and view all the answers

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

True 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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Explore the different types of fungal structures, including hyphae, septa, and specialized hyphae, as well as their relationships with other organisms, such as mycorrhizae.