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Tuesday, December 31

  1. page Fungi edited Fungi Rabya Saraf {pg-20-fungi-alamy_91555t.jpg} (A brilliant man once said: "I'm a 'fu…
    Rabya Saraf
    (A brilliant man once said: "I'm a 'fun-gi'...")
    Fungus and molds are gross, but pretty useful in nature. They get rid of dead organisms and other organic materials which is really important. Fungi are used in many ways by us: for food (mushrooms), antibiotics, for dough rising, and fermentation of wine and beer.
    Fungi are eukaryotes(A eukaryote is an organism whose cells contain complex structures enclosed within membranes) and mostly multi cellular.
    Diagnostic characteristics of the group
    · Fungi are heterotrophs that acquire their nutrients by absorption. Small organic molecules are absorbed from the surroundings.
    · A fungus digests its food by secreting hydrolytic enzymes, called exoenzymes, into the food.
    · This mode of nutrition (absorptive) enables fungi to live as decomposers (saporbes), parasites, and mutualistic symbionts.
    · Saprobic fungi absorb nutrients from nonliving organic material.
    · Parasitic fungi absorb the nutrients from the cells of the living host.
    · Mutualistic fungi also absorb nutrients from a host organism, but they reciprocate with functions beneficial to their partners in some way.
    · Ecosystems depend on fungi as decomposers and symbionts.
    · Some fungi are pathogens.
    · They are also commercially important.
    · Fungi and animals evolved from a common protistan ancestor.
    · Extensive surface area and rapid growth adapt fungi for absorptive nutrition.
    · Fungal cells contain memebrane bound nuclei, cytoplasmic organelles. They reproduce by both sexual and asexual means.
    · A fungal mycelium grows pretty rapidly. The fungus concentrates its energy on expanding and lengthening its hypha. Mycelia are nonmotile but it doesn’t need to move because it keeps growing all the time.
    · Fungi have a worldwide distribution, and grow in a wide range of habitats, including extreme environments such as deserts or areas with high salt concentrations.
    · As well as in deep sea sediments.
    · Most grow in terrestrial environments, but several species live partly or solely in aquatic habitats.
    · Fungi have also been found in hydrothermal areas of the ocean.
    ·Some symbiotic fungi inhabit roots and help deliver nutrients to the host plant. These kinds of fungi are called mycorrhizae and are necessary for the success of the plant.
    Major types
    · The suffix –Mycete, means fungus.
    · Phylum Chytridiomycota
    o Motile spores with flagella
    o Chytrids are mainly aquatic.
    o Absorptive mode of nutrition and walls made of chitin.
    o Most primitive fungi
    - Most are found on organic debris
    - They are most commonly the cause of plant diseases and often cause diseases in frogs and other amphibians.
    {chytrid_csa.jpg} Chytrids
    · Phylum Zygomycota
    o These are zygote fungi.
    o Plasmogamy produces a resistant structure called zygosporangium and it is the sexual stage.
    o Mostly terrestrial and live on soil or decaying organic material.
    o One group that is very important is the mycorrhizae, which forms mutualistic associations with the roots of plants.
    o Are coenocytic. Speta is found only where reproductive cells are formed.
    o Example, black bread mold.
    o Zygomycetes are resistant to freezing and drying and metabolically inactive.
    o They release spores when conditions are favorable.
    {Pilobolus.jpg} Zygomycota
    · Phylum Ascomycota
    o Also called sac fungi
    o Found in marine, freshwater, and terrestrial habitats.
    o Range in complexity and size.
    o Include some of the most devastating plant pathogens.
    o Asexual spores are produced and are dispersed by wind.
    o Sexual spores borne internally in sacks called asci.
    -The shared characteristic that defines the Ascomycota is the ascus. It is within the ascus that nuclear fusion and meiosis take place
    -Reproduces with algae to create lichens
    - accounts for approximately 75% of all fungi
    - some ascomycota form symbiotic relationships, such as mutualistic relationships, with arthropods - the ascomycota line beetle galleries (where they lay their eggs) and can provide nutrition for larvae, and in return, the beetles transport the fungi to newly established galleries and allow the fungi to maintain a pure culture.
    {Aleuria.jpg} Sac Fungi
    · Phylum Basidiomycota
    o Also called club fungus.
    o Examples mushrooms and puffballs.
    o Impotant decomposers of plant material and wood.
    o Periodically the mycelium reproduces sexually.
    o Sexual spores borne externally on club shaped structures called basidia.
    oFeed on decaying decaying dead organic matter, one, for example, wood. This can be problematic for humans because Basidiomycota may feed on wood in buildings.
    oSome may bring diseases to animals
    oPoisonous Basidiomycota contain toxins such as hallucinogens and astaxanthin.
    oThey can be terrestrial or aquatic.
    {PA_ShelfFungus_Terrell_052405.jpg} Club Fungus {}
    o Rapidly growing, asexually reproducing fungus.
    o Example, bread mold.
    o The mycelia grow as saprobes or parasites on the host.
    o Informal group without phylogenetic basis.
    {aspergillus.gif} Mold
    · Yeasts
    o Unicellular fungi that inhabit liquid or moist habitats.
    o Used to raise bread, ferment wine.
    o Some cause problems for us, like yeast on moist surfaces in our homes.
    o Some reproduce asexually while other yeasts reproduce sexually.
    {serveImageFullsize.jpg} Yeasts
    · Lichens
    o A symbiotic association of lots of photosynthetic microorganisms held in a mesh of fungal hyphae.
    o May reproduce sexually of asexually
    o Can live in environments where neither fungi nor algae can grow.
    o Good example of mutual exploitation.
    o Lichens are important in breaking through rock and establish soil trapping. This process makes possible for plants to grow. Lichens are also the major factor in primary succession in areas where no soil is present.
    {lichen_hyphae.gif} Lichen
    · Mycorrhizae
    o Mutualistic associations of plant roots and fungi.
    The symbiotic relationship between the plant roots and the fungus is the bidirectional circulation of nutrients. Carbon (from the plant) flows to the fungus whereas inorganic nutrients (from the fungus) move to the plant.
    The following is a video clip that explains how Mycorrhizal fungi are important to plants.
    o Enormously important in natural ecosystems and agriculture.
    {myco.gif} Mycorrhizae
    Basic anatomy
    · The cells of most fungi grow as tubular, elongated, and thread-like (filamentous) structures and are called hyphae, which may contain multiple nuclei and extend at their tips. New hyphae also extend from existing hyphae, process called branching.
    · The bodies of fungi (except for yeasts which are unicellular) are constructed of tiny filaments called hyphae. Hyphae are composed of tubular walls surrounding plasma membranes and cytoplasm. Fungi are avascular: they do not have a respiratory, digestive, or transportation system. They use the hyphae.
    · The hyphae form a mesh called a mycelium, which is the “feeding network of the fungus.”
    · Fungal mycelia can be huge, usually underground. (Once scientists found a fungus with a 3.4 miles long mycelium).
    · Most fungi are multicelluar with the hyphae divided into compartments separated by cross walls known as septa.
    {hypha.gif} Hyphae
    · The septa can allow ribosomes, mitochondira, and nuclei to move from cell to cell.
    · Some fungi are aseptate. They are called coenocytic fungi and are not divided into separate compartments.
    · Most fungi build this wall out of chitin, a strong and flexible polysaccharide.
    · Parasitical fungi usually have some of their hyphae modified as haustoria, nutrient absorbing hyphal tips that penetrate the tissues of the host cell.
    {31-01-FungalMycelia-CL.jpg} Mycelium
    Transport of materials
    · The nutritionally active bodies of most fungi are organized around and within the tissues of their food sources. They are usually hidden underground. Fungi hyphae extend as they grow. These structures absorb nutrients for use from the host.
    · Specialized hyphae called haustoria parasitize plant cells from the outside and feed on it.
    · The mycelium is the network of a fungus that feeds on the host.
    · Morphological adaptations along with secreted enzymes digest large organic molecules into smaller molecules that may then be absorbed as nutrients.
    Hyphae can contain internal crosswalls, called septa, that divide the hyphae into separate cells. The septa of some species of fungi have pores, which allo cytoplasm to flow freely from one cell to the next. Cytoplasmic movement within the hypha provides a means to transport of materials.
    · Fungi disperse and reproduce by releasing spores that are produced sexually or asexually.
    To initiate mating, fungi communicate with other individuals via pheromones.
    · A huge amount of spores are produced at a time.
    · Mechanism used to disperse spores, for example, can be puffballs, which puff out spores with a great amount of force into the atmosphere. Theses spores may be then carried by wind or water.
    · They will germinate to produce mycelia in a moist place where there is food available.
    · Spores functions in dispersal and account for the widespread geographic distribution of it.
    · Asexual reproduction through vegetative spores or mycelial fragmentation is common; it maintains clone populations adapted to a specific niche.
    · In fungi with sexual life cycles, the union occurs in two stages
    1. Plasmogamy
    2. Karyogamy
    · Plasmogamy is the fusion of the two parents’ cytoplasm when their mycelia come together.
    · Karyogamy is the fusion of the haploid nuclei contributed by two parents.
    · These two stages might be separated by hours or even hundreds of years.
    · During the gap between the two stages, the hybrid exists as a heterkaryon, its haploid nuclei still separate.
    · In some fungi, the haploid nuclei part off, two to a cell, one from each parent. Such a mycelium is said to be dikaryotic, meaning “two nuclei.” Without fusing, the two nuclei in each cell keep dividing until karyogamy takes place.
    {} The Reproduction Cycle of Fungi (Walker K.)
    Environmental adaptations
    · Since fungi cannot move, they make up for this shortcoming by being able to grow rapidly. They extend the hyphae while growing and locate food sources to feed on.
    · They have long, thin structures, hyphae, which can move through compact things like soil or the host. Their hyphae extend into the host cells through which they feed.
    · Spores can survive extreme temperatures.
    · The spores start to grow if they land in a favorable environment.
    - Spores are also used as resistant cells that allow the organism to survive when growth becomes incompatible with environmental conditions.
    Review Questions:
    1) In what ways is fungi reproduction unique to other kingdoms?
    2) How does the structure of a fungus enable it to obtain and transport food and other materials?
    3) What triggers spores to grow?
    4) Explain the symbiotic relationship between vascular plants and mycorrhizae.
    Source used:
    Campbell, Neil A., and Jane B. Reece. Biology, Sixth Edition. 6th ed. San Francisco: Benjamin Cummings, 2001. Print.
    ttp:// Zygomycota chytrids main picture Ascomycota club fungus mold Yeast Lichen Mycorrhizae Reproductive cycle Hphae Mycelium

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Wednesday, October 12

Thursday, October 7

  1. page Bacteria edited Bacteria by liz daley ​ {bacteria.jpg} Diagnostic Characteristics

    Bacteria by liz daley ​ {bacteria.jpg}
    Diagnostic Characteristics
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