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Kingdom Fungi-Introduction. This is a very diverse group of organisms that includes yeasts, molds, rusts, and smuts. Fungi lack chlorophyll and do not carry on photosynthesis. Most are saprobes , although some are parasitic. Kingdom Fungi-Intro.continued.
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Kingdom Fungi-Introduction • This is a very diverse group of organisms that includes yeasts, molds, rusts, and smuts. • Fungi lack chlorophyll and do not carry on photosynthesis. • Most are saprobes, although some are parasitic.
Kingdom Fungi-Intro.continued • Saprobes (shown here), release digestive enzymes that break down food. • Nutrients are then absorbed into the fungal cells. • Parasitic fungi obtain their nutrients directly from their hosts.
General Fungi Characteristics • Consist of threadlike filaments called hyphae. • Hyphae grow in a tangled mass to form the mycelium. • The hyphae are made up of cells containing the cytoplasm.
General Characteristics continued • Fungal cells may or may not have cross walls (partitions). • Cells with cross walls are called septate. • Fungal cells may be multinucleate. • Cell walls are made up of chitin (a polysaccharide) • Reproduction is both asexual and sexual by means of spores. • 80 000 species exist.
The Five Groups of Fungi • The fungi are divided into 5 groups based on their mode of reproduction: • Group 1: Phylum Zygomycota. • Known as the zygomycetes. • Both sexual and asexual reproduction exist. • Hyphae lack crosswalls. But crosswalls do form during gamete production. • Most are saprobes and some are parasitic.
Phylum Oomycota • The Water molds • Most are saprobes and some are parasites on fish. • Some are plant parasites such as the late blight fungus that caused the Irish Potato Famine (1845-1847). • Only group with motile flagellated spores. • Only group with structurally different male and female gametes (sperm and eggs).
Phylum Oomycota continued • Cell walls made of cellulose and not chitin. • Hyphae have no cross walls. • Diploid stage is dominant in their life cycle.
Group 3 Phylum Ascomycota • Largest known group. • Multicellular • Hyphae have cross walls. • Sac fungi form two types of spores: • Sexual Spore-produces in a sac-like structure called the ascus. 8 ascospores per ascus. • Asexual Spore-Produced at the tip of specialized hyphae called conidiophores. The spores are called conidia.
Ergotism-An Ascomycete Disease. • Disease caused by the plant parasite, Claviceps purpurea. • Grows on rye. • Bread made with contaminated rye, causes severe illness in humans.
Ergotism continued • Symptoms include gangrene, nervous spasms and convulsions. • Ergot is used in medicine to cause blood vessels to constrict. • It is the initial source of the psychedelic drug LSD.
Phylum Basidiomycota • The club fungi. • Spores form in a club-shaped structure called the basidium. • The spores are called basidiospores. • Hyphae are divided by incomplete crosswalls. • Cells have two nuclei.
Group 5 Imperfect Fungi • These molds do not fit into the other groups of fungi, as they lack sexual stages in their life cycles and hence are said to be imperfect. • Reproduction is asexual by way of spores. • Some are predatory and trap protists and small round worms.
Mycorrhizae • Many fungi form symbiotic associations with the roots of green plants, by way of mycorrhizae (“fungus-roots”). • Some of these fungi form distinct layers on the outside of roots (ecto-mycorrhizae), while others are deep in the roots.
Mycorrhizae • The fungi get sugars from the plant host. • The plant itself gets nutrients from the fungi, including nitrogen and phosphorous. • The mycorrhizae also protect plants from heavy metals by acting as filters.
The Lichens Lichens are formed when certain algae join with certain fungi. Mr. Algae Mr. Fungus
Lichens-A Symbiotic Relationship Together, the algae and the fungus form a living unit. What we have here is a symbiosis. The algae through photosynthesis produce sugar as a food source, and the fungus provides support and protection from drying.
