EXAM 4 MasteringBiology Chapter 32 Fungus

In most fungi, a _____ divides a hypha into separate cells.

septum

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

(1) Mycelia are made up of small-diameter hyphae that form an interwoven mass, providing more surface area for nutrient absorption. (2) Some fungi can grow as either filamentous or single-celled forms. (3) Some fungi secrete digestive enzymes into the environment and then absorb the digested nutrients. (4) All fungi are heterotrophs; some species live as decomposers and others as symbionts. NOTE: 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.

Individual filaments, or ___(1)___, make up a ___(2)___, the structure through which a multicellular fungus feeds. Some hyphae are divided into cells by ___(3)___; ___(4)___ in the septa allow absorbed nutrients and other cellular contents to flow throughout the mycelium.

(1) hyphae (2) mycelium (3) septa (4) pores

The body of a multicellular fungus consists of a network of ___(1)___, which form an interwoven mass called a ___(2)___. Some hyphae, called ___(3)___, are divided into cells by crosswalls, or septa. ___(4)___ do not have septa; these hyphae consist of a continuous cytoplasmic mass that contains many nuclei and organelles.

(1) hyphae (2) mycelium (3) septate hyphae (4) Coenocytic hyphae

What is the symbiotic relationship that characterizes arbuscular mycorrhizal fungi (AMF)?

AMF provide key nutrients to tree, grass, and shrub roots in exchange for sugar. NOTE: AMF transfer phosphorus, other nutrients, and water to the roots of grassland and tropical forest plants in exchange for sugars.

Cup fungi are in the phylum _____.

Ascomycota

Using the phylogenetic tree, where should the origin of the AMF association occur?

At the base of Glomeromycota NOTE: AMF contain species from Glomeromycota

Where does meiosis occur in a mushroom?

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

Which of the four major types of fungi exhibit alternation of generations?

Chytrids NOTE: Chytrids are the only type of fungi that exhibit alternation of gametophytic and sporophytic generations.

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

False NOTE: 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.

Why are fungi so important to the carbon cycle?

Fungi accelerate the carbon cycle by breaking down wood and thus freeing up carbon atoms NOTE: Some fungi have evolved the ability to digest lignin and cellulose.

Lignin and cellulose provide rigidity to the cell walls of plants. But in most fungi, chitin performs this role. Why is it logical that most fungi don't have lignin or cellulose in their cell walls?

Fungi produce enzymes that degrade cellulose and lignin.

What life cycle step allows fungi to reproduce sexually without gametes?

Fusion of hyphae

Which of the following events occurs first in the development of a spore into a mature mushroom?

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

Which of the following is NOT a reproductive structure in fungi?

Mycelia NOTE: Mycelia are not reproductive in nature; rather, they are the branchlike forms that absorb nutrients and water.

The mycelial growth habit leads to a body with a high surface-area-to-volume ratio. Why is this important?

Mycelia have a large surface area for absorption.

Which is the longest living part of the fungal life cycle?

Mycelium

Which structure is not directly involved in the reproduction of at least one major group of fungi?

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

Which structure allows the growing mushroom to nourish itself?

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

What is the least likely impact the spraying of fungicide would have on soil-dwelling plants and animals?

No impact NOTE: Fungi live in close association with many organisms and would have impacts if missing.

Which term describes the fusion of cytoplasm from two individuals?

Plasmogamy

_____ is the fusion of hyphae.

Plasmogamy

Lawns are sometimes fertilized with nitrate that can be washed into neighboring woodlots by rain. If the trees in that woodlot are associated with EMF, what effect might the excess nitrate have on the fungi and/or trees?

The trees may take up the nitrate directly into their roots and rely less on the fungi.

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

True NOTE: 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.

A mutualistic relationship between plants and fungi can be determined experimentally by _____.

an increase in labeled carbon in fungi NOTE: Fungi benefit by receiving carbon from the plant, while the plant receives phosphorus and nitrogen from the fungi.

_____ in the cell walls of fungi provides a tough, flexible exterior.

chitin

Most fungi are _____.

decomposers NOTE: Fungi obtain nutrients from nonliving organic matter.

Karyogamy produces a _____ zygote.

diploid

Karyogamy produces a _____.

diploid zygote

Fungi produce _____ spores.

haploid

Mycelia produced in asexual reproduction are _____.

haploid NOTE: All asexual forms are 1n.

Fungal mycelia _____.

have a large surface area composed of branching hyphae NOTE: The large surface area of a fungal mycelium is fundamental to an absorptive mode of life.

Each individual filament, or _____ has a small diameter that contributes to feeding efficiency by maximizing the surface-to-volume ratio.

hypha

Basidia produce spores by a process known as _____.

meiosis

In _____, both species in a relationship benefit from the association.

mutualism

A _____ is an interwoven network of small filaments that infiltrates the material on which a fungus feeds.

mycelium

In _____, one species benefits from an association and the other species is harmed.

parasitism

Each septum contains at least one _____, which enables nutrients and other cell contents to flow between cells.

pore

Mushrooms, brackets, and puffballs are examples of structures used for _____.

reproduction NOTE: Each basidium produces four sexual spores.

Which human cells undergo plasmogamy?

sperm and egg

The fundamental reproductive cell produced by fungi is the _______.

spore NOTE: Spores are the dispersal stage in the fungal life cycle and are produced during both asexual and sexual reproduction.

Fungi release digestive enzymes into their _____.

surroundings NOTE: Fungi then absorb the digested nutrients.

The term _____ refers to an ecological relationship between organisms of two different species that live together in direct contact.

symbiosis

Which of these contains two haploid nuclei?

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