Fungi

Basic Information:Fungi are... - eukaryotes - mostly multicellular- sometimes unicellular (yeast)- very diverse with an estimated 1.5 million species- widely spread, having colonized most terrestrial habitats

- Fungi likely evolved from an aquatic, unicellular, flagellated protist 1.5 billion years ago.- All the oldest fungi

Evolutionary History:

fossils are 460 million years old. Perhaps microscopic fungal ancestors fossilized poorly.

- Systematists recognize Fungi and Anamalia as sister kingdoms- Animals, fungi, and their closest common ancestor are opisthokonts- Most fungal diversity may have come from adaptive radiation with land colonization.

Body Structures:- Hyphae are a network of tiny filaments composed of tubular cell walls.- Mycelia are interwoven hyphae that surround and penetrate nutrient sources.- Hyphae are made of chitin.- Specialized hyphae for penetrating hosts called haustoria.

Body Structures:- Septa are cross walls with pores large enough to allow nuclei through that divide the hyphae into cells.- A fungus with septa is septic and one without is coenocytic.- In coenocytic fungi hyphae are continuous plasma with up to thousands of nuclei.

Reproduction: Asexual- Some fungi (molds) can reproduce with spores, which are carried from the parent by air/water.

- Molds grow quickly as mycelia, making spores. - Fungi like yeasts can reproduce by mitosis.- If a fungus has no known sexual stage, it is called a deuteromycete.

Reproduction: Sexual Sporing- Cells are haploid with transient diploid stages. - Begins when hyphae from two different mycelia release pheramones, which bind to receptors. - Hyphae extend toward each other and fuse.- Combining the cytoplasm is called plasmogamy.- Nuclei do not fuse instantly, so the mycelia contain genetically different, coexisting nuclei.- This makes it heterokaryotic. When nuclei pair off two to a cell, it is dikaryotic.

- The amount of time between plasmogamy and karyogamy can be hours or centuries.- In karyogamy, nuclei fuse to form diploid cells, which then go through meiosis.- The mycelia then produce structures that disperse the new spores.

Chytrids (Chytridiomycota)- Live in soil and lakes.- Both saprobes (decomposers) and parsites of protists, plants, and animals.- Unicellular, but occasionally form colonies with hyphae.- Have flagellated spores (zoospores)

Zygomycetes (Zygomycota)- Phylum includes fast growing molds, parasites, and commensal symbionts of animals.- Coenozoic, with the exception of reproductive cells (mostly asexual).- If sexual reproduction occurs, a sturdy structure called zygosporangium is produced. This is a zygote that is multinucleate.- Zygosporangia are resistant to many harsh conditions (i.e. freezing, dry). If conditions become better, they undergo meiosis and germinate.

- Mutualistic relationships between plants and fungi where phosphate ions are exchanged for nutrients are called mycorrhizae.- Ectomycorrhizal fungi surround a root with hyphae and grow into the extracellular spaces of the root cortex.- Endomycorrihizal fungi grow into the cells of the root.

Mutualistic Symbionts

- All glomeromycetes take part in a special type of endomycorrhizae called arbuscular mycorrhizae.- Hyphae extend into tiny tree-like structures in the plant called arbuscules.

Glomeromycetes (Glomeromycota)

- Some are deadly plant pathogens, many are saprobes, others are mutualistic symbionts, and some are even pesticides. - Defining feature of phylum is sexual spores in saclike asci.- Sexual stages are in fruiting bodies called ascocarps.- Usually reproduce asexually using large numbers of spores called conidia.

Ascomycetes (Ascomycota)

- Named for basidium, a cell in which there is a transient diploid stage.- Saprobes, and mostly sexual reproducers.- Exists for long periods of time as a dikaryotic mycelium, until as a result of environmental stimuli, produces fruiting bodies basidiocarps.

Basidiomycetes (Basidiomycota)

-Lichens come from symbiotic bonds between fungi and unicellular photosynthetic organisms like green algae or cyanobacteria.- The fungi often reproduce sexually, but lichen can produce asexually as a unit, by either fragmentation or soredia. - Soredia are clusters of hyphae full of algae.

Lichens

- Saprobes cycle nutrients.- Many fungi are plant pathogens, but a couple protect plants from insects.- Some fungal ailments effect animals (mycosis) - Many plants could not grow without the mutualistic relationships they share with fungi.

Ecological Significance

Picture Citations:http://www.ucmp.berkeley.edu/fungi/chytrids.htmlhttp://news.softpedia.com/news/How-Did-the-Fungi-Evolve-38697.shtmlhttp://www.botany.hawaii.edu/faculty/wong/BOT135/Lect26.htm Works Cited: Cummings, Benjamin, 7th edition. Campbell Biology. New York: Pearson,     1995-2011 "Ecological Roles". Tanelorn. Accessed 11/16/11. Available [Online]     http://www.tanelorn.us/data/mycology/myc_eco.htm