Chapter 31 Biology Homework and Readings

Zoospores

Flagellated spores in chytrids

Fungi form mutualistic relationships with plants and animals. Which of the following is an example of such a relationship?

-Fungi help break down wood in the guts of termites -Fungi help break down plant material in the guts of grazing mammals -Endophytes in leaves produce toxins that deter herbivores -Fungi can help increase drought tolerance in plants

The following statements describe something about the body structures or functions of fungi. Identify those statements that are correct.

-Mycelia are made up of small-diameter hyphae that form an interwoven mass, providing more surface area for nutrient absorption -Some fungi can grow as either filamentous or single-celled forms. -Some fungi secrete digestive enzymes into the environment and then absorb the digested nutrients. -All fungi are heterotrophs; some species live as decomposers and others as symbionts.

Which statement(s) correctly describe(s) the interactions between plants and fungi?

-Plants depend on fungi as mutualistic symbionts -Plants are harmed by fungal pathogens

Chitin

-Strengthens cell walls -strong but flexible polysaccharide -can enhance feeding by absorption

All fungi share

-The way they derive nutrition -many grow by forming multicellular filaments (body structure that plays an important role in how they obtain food)

Fungi nutrition

-heterotrophs (cannot make their own food) -fungi do not ingest (eat) their food -fungi absorb nutrients from environment -secrete hydrolytic enzymes into their surroundings (enzymes break down complex molecules to smaller organic compounds that the fungi can absorb into their cells and use)

Zygomycetes

-includes species of fast-growing molds responsible for causing foods to mold -other live as parasites or neutral symbionts

Yeasts

-most common fungal body structure -multicellular filaments and single cells -often inhabit moist environments where there is a ready supply of soluble nutrients (sugars and amino acids)

Fungi obtain nutrients through

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

Cup fungi are in the phylum

Ascomycota Cup fungi are a type of sac fungus

Plasmogamy is indicated by the letter _____.

B Plasmogamy is the fusion of hyphae.

Where does meiosis occur in a mushroom?

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

The process indicated by the letter _____ produces a diploid structure.

C Karyogamy produces a diploid zygote.

Nucleariids

Consists of amoebas that feed on algae and bacteria

Basidiomycetes

Destructive plant parasites in this phylum

Karyogamy produces a

Diploid zygote Karyogamy is the fusion of nuclei.

Septa

Division of cells by cross-walls -generally have pores large enough to allow ribosomes, mitochondria, and even nuclei to flow from cell to cell

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

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.

Ectomycorrhizal fungi

Form sheaths of hyphae over the surface of a root and typically grow into the extracellular spaces of the root cortex

Chytrids

Found in hydrothermal vent and other marine communities as well as lakes and soil -important mutualists as well -anaerobic chytrids live in digestive tracts of sheep and cattle

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

Fungi are heterotrophic, and plants are autotrophic.

Coenocytic fungi

Fungi lack septa -consist of a continuous cytoplasmic mass having hundreds or thousands of nuclei -results from the repeated division of nuclei without cytokinesis

Molds

Fungi reproduce asexually by growing as filamentous fungi that produce HAPLOID spores by mitosis

arbuscules

Fungi that have specialized branching hyphae that they use to exchange nutrients with their plant hosts

The diploid phase of the life cycle is shortest in which of the following? -Moss -Fungus -Gymnosperm -Angiosperm -Fern

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

Mycosis

General term for an infection in an animal by a fungal parasite

Almost all of the members of this phylum form arbuscular mycorrhizae in a mutualistic partnership with plants.

Glomeromycota Nearly all glomeromycetes form arbuscular mycorrhizae

Fungi produce _____ spores

Haploid

Karyogamy

Haploid nuclei contributed by the 2 parents fuse, producing diploid cells -zygotes form during this

An important example of interaction between fungi and certain other organisms is mycorrhizae, in which the fungal partners

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

The body of most fungi consists of threadlike _____, which form a network called a ____

Hyphae ... Mycelium

Which of the following events occurs first in the development of a spore into a mature mushroom? -a heterokaryotic mycelium forms -haploid nuclei fuse to form a diploid nucleus -hyphae are produced by mitosis -the mycelium forms

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

Mycelium

Interwoven mass formed by fungal hyphae -infiltrates the material on which the fungus feeds -structure maximizes its surface-to-volume ratio, making feeding efficient -grows rapidly

What sexual processes in fungi generate genetic variation?

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

Which structure is not directly involved in the reproduction of at least one major group of fungi? -Asci -Motile spores -Mycelium -Basidium

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

Which structure allows the growing mushroom to nourish itself?

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

Opisthokonts

Name refers to the posterior location of the flagellum in these organisms

Glomeromycetes

Nearly all of them form arbuscular mycorrhizae

Hyphae

Network of tiny filaments -consist of tubular cell walls surrounding the plasma membrane and cytoplasm of the cells

Which term describes the fusion of cytoplasm from two individuals?

Plasmogamy Plasmogamy is the fusion of cytoplasm from different individuals

From the human perspective, which of the following kinds of fungi would be considered the least useful or beneficial? -Truffles -Decomposers -Mycorrhizal fungi -Rusts -Yeasts

Rusts Rusts include destructive plant parasites.

Fungi of the phylum Ascomycota are recognized on the basis of their production of _____ during sexual reproduction.

Saclike structures

Structure of multicellular fungi

The body of a multicellular fungus consists of a network of hyphae, which form an interwoven mass called a mycelium. Some hyphae, called septate hyphae, are divided into cells by crosswalls, or septa. Coenocytic hyphae do not have septa; these hyphae consist of a continuous cytoplasmic mass that contains many nuclei and organelles.

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?

These sexual processes generate genetic variation

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

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.

Plasmogamy

Union of the cytoplasms of 2 parent mycelia

Arbuscular mycorrhizal fungi

extend arbuscules through the root cell wall and into tubes formed by invagination of the root cell plasma membrane

Endophytes

fungi (or bacteria) that live inside leaves or other plant parts without causing harm -most are ascomycetes

Deuteromycetes

fungi lacking sexual reproduction

Dikaryotic

haploid nuclei pair off two to a cell, one from each parent -as it grows, the 2 nuclei in each cell divide in tandem without fusing

mycorrhizae

mutually beneficial relationships between fungi and plant roots

Spores

mycorrhizal fungi colonize soils by dispersing haploid cells called spores -form new mycelia after germinating

Heterokaryon

parts of fused mycelium contain coexisting, genetically different nuclei

Pheromones

sexual signaling molecules that begins sexual reproduction through hyphae from 2 cycelia releasing the signals

Lichen

symbiotic association between photosynthetic microorganism and a fungus in which millions of photosynthetic cells are held in a mass of fungal hyphae

Which of these contains two haploid nuclei? -The heterokaryotic stage of the fungal life cycle -Zygote -Spore-producing structures -Mycelium -Hypha

the heterokaryotic stage of the fungal life cycle