Fungi: Characteristics, Reproduction, and Importance - PDF

+ FUNGI SBI3U1 + What is a Fungus? Eukaryotic organism Can be unicellular or multicellular Often grow out of sight in dark, moist areas (underground or within organisms that can be dead or alive) Part of the kingdom Fungi (very differen...

+ FUNGI SBI3U1 + What is a Fungus? Eukaryotic organism Can be unicellular or multicellular Often grow out of sight in dark, moist areas (underground or within organisms that can be dead or alive) Part of the kingdom Fungi (very different from plants and animals) + Why are Fungi Important? Along with bacteria, fungi are the major decomposers on Earth Responsible for much of the cycling of nutrients in the biosphere and engage in important symbiotic relationships with plants Useful to humans: We eat them – mushrooms and truffles! Used to make bread, soy sauce, and blue cheese Production of alcohol beverages ($$$) “Miracle drugs” – penicillin (antibiotic) and cyclosporine (antirejection) + Fungi Can Also be Harmful! Responsible for some animal and plant diseases Every year about 10 - 50% of the world’s fruit harvest is destroyed by fungi Fungi can rot wood and damage buildings and other structures Common human fungal infections include Athlete’s foot, Ringworm, and Candida (yeast infections) + Classification and Phylogeny Fungi are unlike plants because they: Are not photosynthetic and do not produce their own food Have different methods of reproduction More than 100 000 species have been described Range in size from microscopic single-celled organisms to the largest organisms on Earth Classified into 5 major phyla + Although fungi look similar to plants, they are actually more closely related to animals! + 5 Major Phyla of Fungi Phylum Key Features Chytridiomycota Only fungi with swimming spores Most are saprophytes (lives on dead or decaying matter) Can be single- or multi-celled Zygomycota Include some familiar bread and fruit moulds Most are soil fungi Many are used commercially (i.e. fermentation or pest control) Many are parasites of insects Glomeromycota All form symbiotic relationships (meaning close interaction) with plant roots Ascomycota Many, such as yeast are useful to humans Some cause serious plant diseases Basidiomycota They include mushrooms, puffballs, and bracket fungi Most are decomposers Some form symbiotic relationships with plants + Characteristics Most of the fungus (the “body”) grows underground – we usually only see the reproductive structure that grows out into the air Bodies of most fungi are mesh-like, composed of a branching network of filaments called a mycelium The filaments are called hyphae and are microscopically thin and consist of long tubes of cytoplasm containing nuclei The cytoplasm is contained by a cell wall made of chitin the tubes may be separated into cell-like compartments by cell walls called septa + + Characteristics Cont’d ALL fungi are heterotrophic (they get their energy from other living or dead organisms) They have external digestion Rather than taking food inside their bodies, fungi grow next to (or within) their food source and release digestive enzymes into their surroundings The enzymes digest the food, then the fungi simply absorb the nutrients through the cell membranes of the hyphae + Fungi Characteristics + Fungi Reproduction Can be either sexual or asexual Sexual reproduction involves the fusion of two nuclei two hyphae come into contact with each other to form a dikaryotic cell (dikaryotic = containing two separate nuclei) The dikaryotic cell grows into a new mycelium of cells When mature, the mycelium produces spores (a haploid reproductive cell) that can grow into new organisms on its own However, the majority of fungi reproduce asexually The simplest asexual process is direct fragmentation, or breaking up, of the fungus body Yeast asexually reproduce by budding https://www.youtube.com/watch?v=lTAO5i4Zb6w + Multi-cellular Fungal Reproduction In the case of the basidiomycete, when it becomes mature, it produces spores (as many as 100 million) which are released into the environment. Basidiomycetes experience phases of being haploid, dikaryotic, and diploid. Since spores are airborne, any exposed surface may be covered with spores, and any animal inhaling would inhale fungal spores These spores germinate in favourable conditions + The Life Cycle of a Mushroom A large mushroom can release 100 million spores an hour! + Single-Celled Fungal Reproduction Yeast reproduce by budding, in which the nucleus of one yeast divides, and a cell wall forms between the two nuclei This produces a small daughter cell Often the yeast cells will stay attached to each other forming hypha-like arrangements + Symbiotic Relationships Fungi often live in a symbiotic relationship with other organisms: – Ex. Lichens, the moss-like substance you find on rocks, is a combination of fungi and green algae or cyanobacteria. – Fungi living on/in the roots of plants that help the plant with obtaining nutrients (the symbiotic relationship between the fungus and the plant is called mycorrhiza) Fungi can also live in symbiotic relationships with animals – Ex. The leaf cutter ants Leaf Cutter Ants + Disease Many fungi that feed on living organisms cause disease In humans: athlete’s foot, ringworm infections In plants: may produce toxic chemicals and damage the plant “Zombie” ants + Visual Summary + More on Fungi + Homework Read section 3.1 and add to notes Pg. 85 # 1,2, 4, 5