Chapter 14 Fungi Heterotrophic organisms once considered to be primitive or degenerate plants lacking chlorophyll

Ecological decomposers Importance of Fungi Together with Heterotrophic bacteria Ecological decomposers

Decomposing fruit- Rhizopus

Root-rot fungus- white mycelial causes disease in living trees Acts as decomposers on dead plants

Root rot Ouch!!!

Fungi Composed of Hyphae Heterotrophic absorbers

Characteristics of Fungi Composed of Hyphae Fungal filaments= “Cobwebby” strands of subterranean “white stuff” Mycelium

Fungi form important symbiotic relationships 80% of all vascular plants species from mutually beneficial associations called mycorrhizae between roots and fungi Plant nutrition Lichens form symbiotic relationship with fungi, algal, or cyanobacterial cells

Fungi and insects Endophytes- fungi live in plants produce toxic that protect host

Four phyla of fungi Zygomycota Ascomycota next week lecture Chytridiomycota Zygomycota Ascomycota next week lecture Basidiomycota next week lecture

Chars of Fungi All have cell wall Cell wall composed of polysaccharide- chitin Chitin more resistant to microbial degradation than cellulose

All Fungi Heterotrophic Absorbers Unable to engulf small microorganisms Secrete enzymes and absorb smaller molecules Absorb food mostly at or near the growing tips of their hyphae

Fungi obtain their food Either as Saprophytes or As mutualistic symbionts

Some Obtain energy through fermenation producing ethyl alcohol from glucose (i.e. yeast)

Fungi Store energy Polysaccharide Glycogen Lipids

Fungi reproduce both sexually and asexually Reproduce through the formation of spores that are produced sexually or asexually Most are nonmotile spores Some are dry and small and airborne Some are slimy and stick to the bodies of insects and other arthropods Some propel into air- phototropism

Common method of asexual reproduction in fungi By means of spores Either produced in sporangia The sporangium is a saclike structure, the entire contents of which are converted into one or more spores

Asexual reproduction Or Hyphal cells called conidiogenous cells Spores produced by conidiogenous cells occur singly or in chains called conidia

Asexual repro Some Reproduce by fragmentation of their hyphae

Sexual reproduction Three distinct phases First two are phases of fertilization (syngamy) Plasmogamy- the fusion of protoplasts Karyogamy- the fusion of nuclei (some don’t fuse forming a dikaryon)

Give rise to gametes by differentiation Divide by mitosis gametangia 4 Spores

The last phase is meiosis Sexual reproduction results in the formation of specialized spores such as zygospores, ascospores, basidiospores.

Zygospores Zygospores Asexual and sexual reproduction (by means of haploid spores) Sexually producing zygospores require two compatible species

Zygomycetes: Phylum Zygomycota Live on decaying plant and animal matter in soil Some are parasites of plants, insects or small soil animals Others form symbiotic relationships- endomycorrhizea- with plants occasionally cause infection in animals Rhizopus stolonifer- best known zygomycetes

Life cycle of Rhizopus stolonifer

Gametangia the gamete producing structures are in the Process of producing a zygospore

Zygospore develops within the thick walled zygosporangium