Ch 31

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.

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. Some fungi secrete digestive enzymes into the environment and then absorb the digested nutrients. Some fungi can grow as either filamentous or single-celled forms.

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

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

Hyphae form a network called a mycelium.

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

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

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

Haploid

Diploid zygote Karyogamy is the fusion of nuclei

B Plasmogamy is the fusion of hyphae

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

C Karyogamy produces a diploid zygote

Ascomycota

Plasmogamy Plasmogamy is the fusion of cytoplasm from different individuals.

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

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.

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

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

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

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.

Glomeromycota Nearly all glomeromycetes form arbuscular mycorrhizae.

Sac-like structures The production of saclike structures during sexual reproduction is characteristic of the phylum Ascomycota.

all of the above Fungi enter into these and many other mutualistic relationships with other organisms

Rusts Rusts include destructive plant parasites