Chapter 31 Why did the mushroom go to the party??? Because he’s a fun-gi!

Characteristics of Fungi 1.) All are eukaryotic heterotrophs. 2.) Feed by absorption. a.) Excrete exoenzymes into their environment which break down organic matter into smaller compounds. b.) Fungi then absorb the smaller molecules.

Characteristics of Fungi 3.) Most are multicellular. a.) Exception: single-celled yeasts 4.) Structure of multicellular fungi: a.) Bodies form a network of tiny filaments called hyphae. b.) Hyphae: composed of tubular cell walls surround the plasma membrane & cytoplasm of the cells. i.) Cell walls contain chitin (also found in exoskeletons of insects).

Characteristics of Fungi c.) Hyphae form an interwoven mass called a mycelium which surrounds & infiltrates the organic matter on which the fungus feeds. d.) Mycelia maximize the surface area of the fungus to make feeding more efficient structure/function d.) Mycelia maximize the surface area of the fungus to make feeding more efficient structure/function

Characteristics of Fungi e.) Hyphae are typically divided into individual cells by cross walls called septa. i.) Septa have pores to allow organelles to flow from cell to cell. ii.) Fungi without septa are called coenocytic. Consist of cytoplasmic mass with numerous nuclei.

Characteristics of Fungi 5.) Hyphae can be specialized for various functions: a.) Some can penetrate & feed on living tissues – these hyphae are called haustoria. b.) Mycorrhizal fungi form mutualistic relationships with plants. They deliver ions that plants cannot take up & receive nutrients in return. Most plants have these & do not grow well without them!

Reproduction in Fungi 1.) Most can reproduce either sexually or asexually by producing (usually) A LOT of spores. a.) Nuclei of hyphae & spores are typically haploid. 2.) Sexual reproduction: a.) Hyphae from different mycelia release pheromones & grow toward one another. b.) Hyphae then fuse together – called plasmogamy.

Reproduction in Fungi c.) Haploid nuclei from each “parent” mycelium do not fuse right away. These nuclei coexist & we call the mycelium a heterokaryon (“different nuclei”). d.) Haploid nuclei finally fuse in a process called karyogamy. e.) The “zygote” that is formed usually undergoes meiosis & the mycelium then produces structures that produce & disperse spores (with new combination of genes).

Reproduction in Fungi 3.) Asexual reproduction: a.) Most fungi can do this as well as sexually reproduce. b.) Molds reproduce asexually much of the time. c.) Yeast reproduce asexually by simple cell division or “budding.”

Fungal Evolution 1.) Fungal ancestor was most likely a single-celled, flagellated protist. 2.) Fungi & animals are more closely related to each other than to other eukaryotes. Share a common ancestor & diverged about 1.5 bya.

Fungi Phylogeny

Types of Fungi 1.) Chytrids – mostly aquatic. Can be saprobes or parasites. a.) Unique for producing flagellated spores called zoospores.

Types of Fungi 2.) Zygomycetes – includes molds common on fruits or bread. a.) Produce spores called zygosporangia – resistant to harsh environments.

Types of Fungi 3.) Glomeromycetes: all form a type of mycorrhizae present in about 90% of plants. a.) Actually penetrate cell walls of plant root cells.

Types of Fungi 4.) Ascomycetes: commonly called sac fungi. Morels, yeasts, truffles a.) Produce spores in “sacs” called asci. b.) Some are plant parasites, some important saprobes, many live symbiotically in algae in what is commonly called a lichen.

Types of Fungi 5.) Basidiomycetes: mushrooms & shelf fungi, molds, plant parasites called smuts. a.) Mushroom is actually a reproductive body sprouted by mycelium. Can grow quickly – overnight.

Fungal Impacts on Ecosystems & Humans 1.) Decomposers 2.) Symbiotic Relationships a.) Mycorrhizae – almost all vascular plants have them & depend on them to increase absorption of water, minerals. b.) With ants & termites: “farm” fungus by feeding it pieces of leaves. Fungi break down leaves into substance digested by insects.

Fungal Impacts on Ecosystems & Humans c.) Lichens: algae (or cyanobacteria) & fungus found growing on rocks, logs, etc in close association with one another. Some of 1 st organisms to colonize new environments & form soil. 3.) Pathogens a.) Most fungi pathogens are plant parasites. b.) 2 types of ascomycetes are responsible for killing millions of elms and chestnuts.

Fungal Impacts on Ecosystems & Humans c.) Many parasitize crops – some producing chemicals that are toxic to humans. i.) Parasite of rye can cause ergotism: gangrene, spasms, burning sensations, hallucinations & temporary insanity…one compound from this fungus is a raw material used to make LSD.

Fungal Impacts on Ecosystems & Humans d.) Few species parasitize humans - called mycosis (fungal infection)… i.) Skin mycoses: Ringworm, athlete’s foot ii.) Systemic mycoses: spread through body causing serious illness.

Fungal Impacts on Ecosystems & Humans 5.) Practical Uses of Fungi: a.) Food – mushrooms, used to ripen chesses, used to produce citric acid for soda. Yeast is used to produce alcohol & raise bread b.) Extracts are used as medicines (penicillin is from a mold)