Biology: Fungus

• most multi-nucleated
• can be unicellular (best example of unicellular: yeasts)
• heterotrophic by absorption (animals are heterotrophic by ingestion) -- external digestion
• Most fungi are saprotrophic decomposers feeding on waste products and dead remains of plants and animals
• Some are parasitic towards plants and animals
• Examples of fungi causing human diseases: athletes foot, ringworm, and yeast infections
• Several types of fungi have mutualistic relationships with the roots of seed plants
• -Fungi acquire inorganic nutrients for plants, and in return plants give them organic nutrients.
• Can reproduce sexually or asexually

• non-motile body of a fungus is a mycelium made up on hyphae
• hyphae give the mycelium a large surface area per volume of cytoplasm---helps with absorption
• can have cross walls called septate.
• Nonseptate fungi are multinucleated.

• Similarities/Differences between Plants
• lack chloroplasts
• cell wall contains chitin,NOT cellulose
• energy is stored as glycogen, NOT starch
• fungi are non-motile,
• lack basal bodies, and do not grow a flagella at any life cycle
• move towards food by growing towards it

• haploid hyphae---dikaryotic stage---- diploid zygote
• *all by meiosis

During sexual reproduction, hyphae from two different mating types make contact and fuse. You would expect the nuclei from two mating types to fuse immediately, however in some species, they do not fuse for days, months, and/or years. The nuclei continue to divide in such a way that every cell has one of each nucleus. A hypha that contains paired haploid nuclei is called n+n or dikaryotic. When the nuclei do eventually fuse, the zygote undergoes meiosis prior to spore formation. Fungal spores germinate directly into haploid hyphae without any noticeable embryological development.

• Asexual reproduction usually involves the production of spores by a single mycelium.
• Asexual reproduction can also occur by fragmentation--a portion of a mycelium begins a life of its own.

*Unicellular yeasts reproduce asexually by budding; a small cell forms and gets pinched off as it grows to full size


*nonmotile spores form during both asexual and sexual reproduction

Red Algae

*Both lack flagella in all stages of life cycle.

• lack septa except when filaments border reproductive filaments
• mainly saprotrophs living off of plants and animal remains
• Zygomycetes reproduce sexually by fusion of hyphae from different strains, followed by plasmogamy, karyogamy, and meiosis

Best example: Bread mold: Rhizopus stolonifer

Plasmogamy

Karyogamy

• *are saprotrophs
• play an essential ecological role by digesting resistant (not easily decomposed) materials containing cellulose, lignin, or collagen
• have septa
• usually produce asexually condiospores. There are sporangia in ascomycetes and the condiospores develop directly on the tips of modified aerial hyphae. When released, they are windblown
• *During sexual reproduction, asci within a fruiting body produce spores

*Phylum name refers to the ascus, a fingerlike sac that develops during sexual reproduction. Ascus-producing hyphae remain dikaryotic except in the walled off portion that becomes the ascus where nuclear fusion and meiosis takes place. When mitosis follows meiosis, each ascus contains eight haploid nuclei and produces eight ascospores. The asci are usually surrounded and protected by sterile hyphae within a fruiting body called an ascocarp. A fruiting body is a reproductive structure where spores are produced and released.

Examples: yeasts, red bread molds, cup fungi, (morels and truffles --used in delicacies)

Ethanol and Carbon Dioxide

• reproduce asexually by forming conidiospores
• *Condiospores are produced at the tips of modified aerial hyphae and NOT in sporangia.
• *called "imperfect" because no sexual reproduction has been observed yet.

*Best example: Penicillium: reproduce asexually by forming condiospores.

• an association between fungi and algae (chlorophyta: green algae, or cyanobacteria)
• *used to believe that fungus and alga have a mutualistic relationship, however experimentation suggests controlled parasitism by the fungus on alga
• *reproduce asexually
• can live in areas of extreme conditions and contribute to the formation of soil.

• Term refers to an association between a fungus and the roots of a plant.
• The fungus helps the plant absorb minerals, and the plant supplies the fungus with carbohydrates.
• *Plants whose roots are invaded by mycorrhizas grow more successfuly in poor soils-particularly soil deficient in phosphate, than do plants without mycorrhizas