Important words and concepts from Chapter 31, Campbell & Reece, 2002 (3/25/2005):

by Stephen T. Abedon (abedon.1@osu.edu) for Biology 113 at the Ohio State University

Course-external links are in brackets Click [index] to access site index Click here to access text’s website Vocabulary words are found below

(1) [fungi as herbs] [introduction to fungi: of athlete’s foot, champignons, and beer] [forest pathology and control: fungi, an introduction] [fifth kingdom on-line] [Tom Volk's Fungi] [Nathan’s fungi photo index] [the tree of life fungi page]

(2) Chapter title: Fungi

(a) Fungi are heterotrophs

(b) Unlike animals, "A fungus digests food outside its body by secreting powerful hydrolytic enzymes into the food. The enzymes decompose complex molecules to the simpler compounds that the fungus can adsorb and use."

(c) There exist three fungal niches

(i) Saprobes (i.e., absorbing nutrients from no longer living organisms)

(ii) Parasites (i.e., absorbing nutrients of or derived from still living organisms, to the detriment of the organism being parasitized)

(iii) Mutuals (i.e., absorbing nutrients from still-living organisms, but providing something in return, such as protection or nutrients)

(d) Fungi are typically terrestrial (they probably, to a large extent, evolved on land)

(e) Fungi are key decomposers of plant material

(f) Most fungi derive their nutrition from plant material rather than from animals

(g) Fungi have cell walls made of chitin

(h) [fungi (Google Search)] [index]

FUNGAL ANATOMY

Some Fungal Anatomy: An Overview
Antheridia^*	Male-like donor of haploid nuclei (see Figure 31.8)
Asci	Sac-fungus sexually produced spore-containing structures
Ascocarp	Sac-fungus fruiting body (asci-containing structures)
Ascogonia^*	Sac-fungus female-like receiver of haploid nuclei from sac-fungi antheridia (Figure 31.8)
Ascospores	Sac-fungus haploid dispersal stage (spores)
To put the above in more familiar terms: Antheridia (boys) plus Ascogonia (girls) leads to the production of Ascocarp (~womb/mushroom equivalent) that contain Asci (~placenta/basidia equivalent) that contain Ascospores that are the sexually produced haploid dispersal stage of the sac fungi while the Conidia (defined below) are the asexually produced haploid dispersal stage of sac fungi (see Figure 31.8)
Basidia	Club-fungus asci equivalent (spore-containing structure)
Basidiocarp	Club-fungus basidia-containing structure
Coenocytic	A fungal hyphae that lacks septa
Conidia^*	Sac-fungus asexually produced spores (they don't come from asci)
Dikaryon	A fungus (cell, hyphae, or mycelia) that contains haploid nuclei sourced from different parents
Gametangia^*	Gametangia are the sexual organs of fungi and plants (note the common "gamet-" between gamete and gametangia); these are the supplies of haploid nuclei that ultimately will fuse (karyogamy) to form the diploid precursor to meiosis
Hyphae	Hyphae are the filamentous cells or linked-together cells that represent the bulk of the bodies of molds and macrofungi (e.g., mushrooms)
Mycelium	Mycelia are tangled masses of hyphae typically found growing within a fungal food source
Septa (septum)	These are crosswalls that separate (distinguish) the cells within hyphae; not all fungi possess crosswalls within all of their hyphae
^*Don't worry about knowing the above asterisk-denoted terms.

(3) Hyphae

(a) The dominant structural motif of fungi (except the yeasts) is the hyphae

(b) Hyphae are long, multinucleated, typically multicelled, one-cell thick fungal tissue

(c) Hyphae are typically hidden from sight since fungi grow their hyphae into their food, releasing exoenzymes and absorbing nutrients

(d) In addition, hyphae serve as vascular channels along which nutrients are passed

(e) See Figure 31.2, Examples of fungal hyphae

(f) Hyphae (from aquatic fungus):

(g) [hyphae (Google Search)] [index]

(4) Mycelium

(a) An interwoven mat consisting of many intertwined hyphae is called a mycelium

(b) "A fungal mycelium grows rapidly, adding as much as a kilometer of hyphae each day as it branches within a food source. Such fast growth is possible because proteins and other materials synthesized by the entire mycelium are channeled by cytoplasmic streaming to the tips of the extending hyphae. The fungus concentrates its energy and resources on adding hyphal length rather than girth."

(c) See Figure 31.1, Fungal mycelia

(d) A tangled mass of hyphae:

(e) [mycelium (Google Search)] [index]

(5) Septa

(a) The crosswalls that delineates individual fungi cells, within hyphae, are called septa (sing. = septum)

(b) Septa typically possess pores through which cytoplasm can flow

(c) Pores can vary in size with some fungi actually lacking septa altogether

(d) See Figure 31.2, Examples of fungal hyphae

(e) Septa within hyphae:

(f) [fungus septa (Google Search)] [fungus septa (Google Search)] [index]

(6) Coenocytic

(a) The absence of septa within hyphae is called coenocytic

(b) We see this word again when discussing plasmodial slime molds which possess multiple nuclei within a single (very large) cytoplasm

(c) See Figure 31.2, Examples of fungal hyphae

(d) [coenocytic (Google Search)] [index]

FUNGAL REPRODUCTION

(7) Reproduction (generalized fungal life cycle)

(a) All fungi reproduce by mitosis

(b) Most fungi additionally reproduce by meiosis

(c) One way fungi disperse is by releasing haploid spores, the products of either mitosis or meiosis

(d) Mating is accomplished via the growing together of hyphae sourced from different parents

(e) Hyphae fusing together (fungi mating = plasmogomy); numbers are in minutes:

(f) We can summarize a generalized fungal life cycle as follows (ploidy is in parentheses):

(i) Sexual reproduction (note: order of terms is relevant):

· mitosis

· Hyphae (ploidy = n)

· mitosis

· Mycelium (ploidy = n)

· Plasmogamy (a process) (= fusion of cytoplasm)

· Dikaryotic stage (ploidy = n + n) (occurs within zygosporangia for Zygomycete, ascogonia for Ascomycete, or hyphae for Basidiomycete)

· mitosis

· Karyogamy (a process) (= fusion of haploid nuclei)

· Diploidy (ploidy = 2n) (occurs within zygosporangia for Zygomycete, ascocarps for Ascomycete, or basidiocarps for Basidiomycete)

· Meiosis (a process)

· Spore-producing structures (ploidy = n) (= sporangium for Zygomycete, asci for Ascomycete, or basidia for Basidiomycete)

· Spores (ploidy = n) (= spores for Zygomycete, ascospores for Ascomycete, or basidiospores for Basciomycete)

· Germination (a process)

· mitosis

· Hyphae (ploidy = n)

· mitosis

· Mycelium (ploidy = n)

Overview of Fungi Asexual Reproduction

mitosis (m) à Hyphae à (m) à Mycelium à (m) à

[ Spore-producing structures à (m) à Spores à ]

Germination à (m) à Hyphae à and so on

Overview of Fungi Sexual Reproduction

mitosis (m) à Hyphae à (m) à Mycelium à

[ Plasmogamy à Dikaryon à (m) à Karyogamy à Diploidy à Meiosis à Spores à ]

Germination à (m) à Hyphae à and so on

(ii) Asexual reproduction (note: order of terms is relevant):

· mitosis

· Hyphae (ploidy = n)

· mitosis

· Mycelium (ploidy = n)

· mitosis

· Spore-producing structures (ploidy = n)

· mitosis

· Spores (ploidy = n) (= conidia for sac fungi)

· Germination (a process)

· mitosis

· Hyphae (ploidy = n)

· mitosis

· Mycelium (ploidy = n)

(g) See Figure 31.3, Generalized life cycle of fungi

(h) Shown is sexual portion of life cycle:

(i) [fungus reproduction (Google Search)] [index]

(8) Ploidy

(a) Fungi typically possess haploid nuclei, except just prior to