Saddleback BIO 3B - Laboratory Fungal Diversity (5 pages)

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Laboratory Fungal Diversity



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Laboratory Fungal Diversity

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5
School:
Saddleback College
Course:
Bio 3b - General Biology II
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Biology 3B Laboratory Fungal Diversity Objectives To describe the general characteristics of the phyla in the kingdom Fungi To learn the anatomy life cycle and identification of representative fungal organisms To discuss the ecological role and economic importance of fungi Introduction The kingdom Fungi is one of four kingdoms in the domain Eukarya This kingdom consists of over 70 000 identified species with estimates over 1 5 million fungal species This kingdom consists of a diverse group of organisms that range from unicellular yeasts to multicellular most organisms Fungi are economically and ecologically important Economically fungi are beneficial in that they are used to produce various food items leaven bread cheeses etc medicines beverages etc Some fungi are parasitic on plants and animals Numerous fungi have even cause widespread famine or diseases as a result of infestations potato famine ergotism All members are heterotrophic where many obtain their nutrients by releasing exoenzymes into their surrounding environment to breakdown food items outside the body and then absorbing the nutrients into their cells Fungi that feed on dead organic material are referred to as saprobes and comprise one of the principal decomposers one Earth Parasitic fungi that found on other living organisms have specialized structures called haustoria haustorium singular to penetrate the host organism for nutrient absorption There are still other fungi that form a mutualistic relationship with another organism while a few are even predators of nematode worms Although fungi were once classified with plants fungi have several major differences from plants As mentioned before fungi are heterotrophic Like plants all fungi have cells walls however fungal cell walls are composed of chitin instead of cellulose Fungal bodies vegetative are composed of long slender filaments called hypha hyphae plural which form more complex structure when compacted together In most fungi the hyphae form a tangled mass called a mycelium mycelia plural These hyphae can be completely separated by septa septum singular or incompletely separated thus allowing for communication between adjacent filaments As a result of this incomplete separation this is why most fungi grow very rapidly when there is ample water and nutrients present Some fungi have no separations at all aseptate and thus are multinucleated coenocytic Fungi can reproduce both sexually and asexually Figure 1 In either case haploid spores are produce When these spores land on a suitable substrate they germinate divide via mitosis into a mature haploid organism During asexual reproduction reproductive structures such as sporangia and conidia produce spores via mitosis Two other forms of asexual reproduction include budding as seen in the imperfect fungi i e yeasts and by fragmentation of the hyphae Figure 1 Generalized fungal lifecycle Biology 3B Laboratory Fungi There are three distinct phase in sexual Page 1 of 5 reproduction haploid diploid and the heterokaryotic dikaryotic phase Gamete producing cells gametatangium gametatangia in the haploid organism produces haploid gametes via mitosis Gametes from different organisms then fuse forming a diploid zygote that undergoes meiosis to form haploid spores When these spores land on a suitable substrate they germinate forming the mature haploid organism beginning the process again Scientists that study fungi are called mycologists They have separated the kingdom Fungi into four distinct phyla and one non taxonomic group These are Part A Phylum Chytridiomycota chytrids This phylum includes about 790 aquatic species that are commonly called chytrids Many chytrids are either saprobes or parasites Members in this phylum were once excluded from being classified as fungi because of flagellated zoospores However more recent molecular data supports classifying chytrids as a primitive fungus instead of with fungus like protists Chytrids have cell walls composed of chitin like other fungi They also utilize similar enzymes and metabolic pathways as other fungal groups It has even been hypothesized that chytrids may be the link between protists and fungi Examine chytrids if available Part B Phylum Zygomycota Zygote fungi zygomycetes There are approximately 600 species of zygote fungi categorized in this group due to the resting sexual spores called zygospores Most zygomycetes are terrestrial found living in the soil or are saprobic on decaying plant animal matter Zygomycetes that have mutualistic relationships with plant roots are often referred to as mycorrhizae Rhizopus stolonifer is the black bread mold that most are familiar with Their hyphae have modifications called rhizoids that penetrate the substrate Hyphae are connected via structures called stolons Hyphae filaments that become upright are called sporangiophores asexual that terminates at the columella Surrounding the columella is the sporangium sporangia plural that produces the asexual haploid spores R stolonifer is heterothallic possessing opposite strains or and can reproduce sexually when conditions become less ideal This requires that and hyphae fuse see Figure 31 7 in Campbell and Reece Then hormones cause these hyphae to develop gametatangia which will become separated from the fungal body The nuclei fuse forming a diploid zygote that develops into the zygospore The zygospore is protected by the thick walled zygosporanganium that is resistant to harsh conditions desiccation temperature etc When the zygosporangium matures a sporangium germinates from the zygospore It is during this time when spores are produced via meiosis and released into the surrounding environment Be able to identify and the know the functions of the following on live and prepared slides o Rhizoids stolons hyphae columella sporangiophore sporangium gametatangia zygospore zygosporangium o Know the portion of the lifecycle n 2n the particular structure is from Biology 3B Laboratory Fungi Page 2 of 5 Part C Phylum Ascomycota Sac fungi ascomycetes There are over 60 000 described species of sac fungi that range in size from unicellular yeasts to cup fungi morels and truffles Sac fungi can be found in a variety of habitats from terrestrial to both freshwater and marine environments More than half of the sac fungi species form a mutualistic relationship typically with a green algae called lichens Others fungi may form mycorrhizae associations with plant roots Still many other sac fungi are saprobes


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