Ecological Roles Of Fungi PDF

# Ecological Roles of Fungi - Fungi, together with bacteria, are the principal decomposers in the biosphere - Fungi are virtually the only organisms that can break down lignin and cellulose - Fungi cause animal diseases - Fungi are the most harmful pests of living plants - 1 hectare = 10,000 squa...

# Ecological Roles of Fungi - Fungi, together with bacteria, are the principal decomposers in the biosphere - Fungi are virtually the only organisms that can break down lignin and cellulose - Fungi cause animal diseases - Fungi are the most harmful pests of living plants - 1 hectare = 10,000 square meters = 107,639 square feet = 2.471 acres - Armillaria: One of the world's largest organisms # General Biology of Fungi - Fungi are heterotrophs and absorb nutrients from outside of their body - Fungi use enzymes (exoenzymes) to break down a large variety of complex molecules into smaller organic compounds in unexploited organic matter - The versatility of these enzymes contributes to fungi's ecological success - Fungi can breakdown cellulose and lignin - They are essential for the well-being of most terrestrial ecosystems because they break down organic material and recycle vital nutrients # Fungal Morphology - Fungi consist of mycelia, networks of branched hyphae adapted for absorption, and are usually underground - Most fungi have cell walls made of chitin, a mucopolysaccharide, which is the same material that make up the protective coats of arthropods - Fungi exhibit diverse lifestyles: - Decomposers - Parasites - Mutualists - The most common body structures are multicellular filaments (mushrooms) and single cells (yeasts) # Reproduction - Sexual reproduction requires the fusion of hyphae from different mating types - Fungi use sexual signaling molecules called pheromones to communicate their mating type, like many animals such as Bombyx moth, ants, and mammals - Plasmogamy is the union of two parent mycelia - In most fungi, the haploid nuclei from each parent do not fuse right away; they coexist in the mycelium, called a heterokaryon - Hours, days, or even centuries may pass before the occurrence of karyogamy, nuclear fusion - During karyogamy, the haploid nuclei fuse, producing diploid cells # Asexual Reproduction - In addition to sexual reproduction, many fungi can reproduce asexually - Molds produce haploid spores by mitosis and form visible mycelia - Other fungi that can reproduceasexually are yeasts, which inhabit moist environments - Instead of producing spores, yeasts reproduce asexually by simple cell division and the pinching of "bud cells" from a parent cell # The Origin of Fungi - The ancestor of fungi was an aquatic, single-celled, flagellated protist - Fungi are more closely related to animlas than they are to plants # Phylogenetic Tree of Fungi | Phylum | Species | Description | |------------------------------|----------|-----------------------------------------------------------------------------------------------------------------------------------------------------| | Chytrids (Chytridiomycota) | 1,000 | They are found in freshwater and terrestrial habitats. They can be decomposers, parasites or mutualists | | Zygomycetes (Zygomycota) | 1,000 | They include fast-growing molds, parasites, and commensal symbionts. They are named for their sexually produced zygosporangia | | Glomeromycetes (Glomeromycota) | 160 | They are now classified in a separate clade. They form arbuscular mycorrhizae (endomycorrhizae) | | Ascomycetes (Ascomycota) | 65,000 | They live in marine, freshwater, and terrestrial habitats. They are commonly called sac fungi. They vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels | | Basidiomycetes (Basidiomycota) | 30,000 | | # Ecology of Fungi - **Arbuscular (endomycorrhizae) mycorrhizae** - Hyphae penetrate the root cell wall - By far the most common (70% of all species of mycorrhizae) - Fungal partners are Glomeromycetes - **Ectomycorrhizae** - Hyphae surround but do not penetrate the root cells - Most hosts are forest trees (pines, oaks) - Fungal partners are mostly Basidiomycetes (30% of the mycorrhizae) ## Mycorrhizae (Fungus-Roots) - Symbiotic association between a fungus and the roots of plants - Fungus helps plant absorb minerals and nutrients. - Plant provides fungus with food(organic molecules). - Fungal hyphae surround or penetrate roots and supplement their increased absorptive surface area - Increase plant growth - Mycorrhizae are mutually beneficial relationships between fungi and plant roots - Ectomycorrhizal fungi form sheaths of hyphae over a root and also grow into the extracellular spaces of the root cortex. - Arbuscular mycorrhizal (Endomycorrhizae) fungi extend hyphae through the cell walls of root cells and into tubes formed by invagination of the root cell membrane # Chytrids - Chytrids are unique among fungi in having flagellated spores, called zoospores - Powerful decomposers - Digest cellulose in ruminant digestive tract. Anerobic chytrids start digesting the cellulose in a cow's grassy meal - They also digest chitin and keratin. - Contribute to ongoing worldwide amphibian decline - Lethal skin infection, Batrachochytrium dendrobatidis cause a disease called cutaneous chytridiomycosis in frogs # Zygomycete - Some zygomycetes, such as Pilobolus, can actually "aim" their sporangia toward conditions associated with good food sources. - The zygomycetes (phylum Zygomycota) exhibit great diversity of life histories. - They include fast-growing molds,parsites, and commensal symbionts. - The zygomycetes are named for their sexually produced zygosporangia. - Zygosporangia, which are resistant to freezing and drying, can survive unfavorable conditions. - Black Bread Mold, Rhizopus stolonifer - Reproductive structure is a zygospore # Glomeromycetes - The glomeromycetes (phylum Glomeromycota) were once considered zygomycetes. - They are now classified in a separate clade. - Glomeromycetes form arbuscular mycorrhizae (endomycorrhizae) # Ascomycetes - Ascomycetes (phylum Ascomycota) live in marine, freshwater, and terrestrial habitats - The phylum is defined by production of sexual spores in saclike asci, usually contained in fruiting bodies called ascocarps - Ascomycetes are commonly called sac fungi - Ascomycetes vary in size and complexity from unicellular yeasts to elaborate cup fungi and morels - Ascomycetes include plant pathogens, decomposers, and symbionts - Ascomycetes reproduce asexually by enormous numbers of asexual spores called conidia - Include economically important ascomycetes - Penicillium - Penicillin - Blue cheeses - Aspergillus - Soy sauce - Soy paste # Yeasts - Yeasts are unicellular ascomycetes - Most reproduce asexually by budding - Yeasts can ferment carbohydrates - Break down glucose into ethanol and CO2 - Used to make bread, beer and wine - Saccharomyces cerevisiae