Characteristics

• Eukaryotic 
• Do not contain chlorophyll
• Nonphotosynthetic
• Absorptive heterotrophs - digest food first & then absorb it into their bodies
• Release digestive enzymes to break down organic material or their host
• Store food energy as glycogen
• Most are saprobes – live on other dead organisms
• Important decomposers & recyclers of nutrients in the environment
• Most are multicellular, but some unicellular like yeast
• Some are internal or external parasites; a few are predators that capture prey
• Nonmotile
• Lack true roots, stems, & leaves
• Cell walls are made of chitin (a complex polysaccharide)
• Grow as microscopic tubes or filaments called hyphae that contain cytoplasm & nuclei
• Hyphal networks are called mycelium
• Some are edible
• Reproduce by sexual & asexual spores
• Antibiotic penicillin comes from Penicillium mold
• Classified by their sexual reproductive structures
• Grow best in warm, moist environments preferring shade
• Mycology – study of fungi
• Fungicide – chemicals used to kill fungi
• Includes yeasts, molds, mushrooms, ringworm, puffballs, rusts, smuts, etc.
• Fungi may have evolved from prokaryotes by endosymbiosis

Vegetative (nonreproductive) Structures of Fungi

• Body of a fungus made of tiny filaments or tubes called hyphae

• Hyphae contain cytoplasm & nuclei and has a cell wall of chitin

HYPHAE

• Each hyphae is one continuous cell

•  Hyphae continually grow & branch

• Septum (septa-plural) are cross walls with pores to allow the movement of cytoplasm in hyphae

• Hyphae with septa are called septate hyphae

• Hyphae without septa are called coenocytic hyphae

• Tangled mats of hyphae are known as mycelium

• All hyphae within a mycelium share the same cytoplasm so materials move quickly

• Hyphae grow rapidly from the tips by cell division

• Stolon is a horizontal hyphae that connects groups of hyphae to each other

• Rhizoids are rootlike parts of hyphae that anchor the fungus

Reproductive Structures

• Most fungi reproduce asexually & sexually
• Asexual reproduction produces genetically identical organisms & is the most common method used
•  Sexual reproduction in fungi occurs when nutrients or water are scarce
• Fruiting bodies are modified hyphae that make asexual spores
• Fruiting bodies consist of an upright stalk or sporangiophore with a sac containing spores called the sporangium

SPORANGIOPHORES

• Types of fruiting bodies include basidia, sporangia, & ascus
• Spores – haploid cells with dehydrated cytoplasm & a protective coat capable of developing into new individuals
• Wind, animals, water, & insects spread spores
• When spore lands on moist surface, new hyphae form

Asexual Reproduction in Fungi

• Fungi reproduce asexually when environmental conditions are favorable
• Some unicellular fungi reproduce by mitosis
• Yeast cells reproduce by budding where a part of the cell pinches off to produce more yeast cells

• Athlete’s foot fungus reproduce by fragmentation from a small piece of mycelium
• Most fungi reproduce asexually by spores
• Penicillium mold produces spores called conidia without a protective sac on the top of a stalk called the conidiophore

Sexual Reproduction in Fungi

• Fungi reproduce sexually when environmental conditions are unfavorable
• No male or female fungi
•  Two mating types --- plus (+) and minus (-)  
• Fertilization occurs when (+) hyphae fuse with (-) hyphae to form a 2N or diploid zygote
• Some fungi show dimorphism (ability to change their form in response to their environmental conditions)

Classification of Fungi

• Fungi are classified by their reproductive structures
• The 4 phyla of fungi are Basidiomycota, Zygomycota, Ascomycota, & Deuteromycota

Zygomycota

• Called sporangium fungi or common molds
• Includes molds & blights such as Rhizopus stolonifer (bread mold)

• No septa in hyphae (coenocytic)
• Asexual reproductive structure called sporangium & produces sporangiospores
• Rhizoids anchor the mold, release digestive enzymes, & absorb food  
• Asexual reproductive structure called sporangium & produces sporangiospores
• Sexual spore produced by conjugation when (+) hyphae & (-) fuse is called zygospore
• Zygospores can endure harsh environments until conditions improve & new sporangium

Basidiomycota

• Called club fungi

•  Includes mushrooms, toadstools, puffballs, bracket fungi, shelf fungi, stinkhorns, rusts, & smuts

• Some are used as food (mushroom) & others cause crop damage (rusts & smuts)

• Seldom reproduce asexually

• Basdiocarp made up of stalk called the stipe & a flattened cap

• Stipe may have a skirt like ring below cap called the annulus

• Gills are found on the underside of the cap & are lined with basidia

• Basidium – sexual reproductive structure that make basidiospores

• Basidiospores are released from the gills & germinate to form new hyphae & mycelia

• Vegetative structures found below ground & include rhizoids (anchor & absorb nutrients), hyphae, & mycelia

Ascomycota

• Called sac fungi

• Includes yeast, cup fungi, truffles, powdery mildew, & morels

• Some are parasites causing Dutch elm disease & chestnut blight

• Sac Fungi can reproduce both sexually and asexually

•  Yeast reproduce asexually by budding (form small, bud-like cells that break off & make more yeasts)

• Asexual spores called conidia form on the tips of specialized hyphae called condiophores

• Ascocarp – specialized hyphae formed by parent fungi during sexual reproduction

• Ascus – sacs within the ascocarp that form spores called ascospores

Lichens

• Symbiotic association between a sac fungus & a photosynthetic green algae or cyanobacteria
• Both organisms benefit (algae makes food & fungus supplies moisture, shelter, & anchorage)
• Grow on rocks, trees, buildings, etc. & help form soil
• Crustose lichens grow on rocks & trees; fructose lichens grow shrub-like; foliose lichens grow mat-like on the soil

Mycorrhizae

• Symbiotic association of a fungus living on plant roots
• Most plants have mycorrhizae on their roots
• Fungus absorbs sugars made by plant
• Plants absorb more water & minerals with aid of the fungus

Importance of Fungi

• Fungal spores cause allergies
• Molds, mildew, rusts, & smuts damage crops
• Yeasts are used to make beer & bread
•  Antibiotic penicillin
• Decomposers & recyclers of nutrients
• Mushrooms eaten as food
• Help form blue cheeses
• Aspergillus is used to make soy sauce
• Cause athlete’s foot & ringworm
• Amanita is poisonous mushroom
• Can cause yeast infections