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7.2: Introduction

  • Page ID
    40191
  • Fungi are a group of organisms that can be characterized by their uniqueness. They are non-photosynthetic so they are not plants; they are heterotrophs that secrete enzymes into their environment and then absorb the broken down nutrients. However, they aren’t animals, though most closely related to them, nor are they protists. They are often saprophytic and live on dead and decaying material, or they may be pathogens and parasites that infect plants and animals alike. Fungi have cells walls made of chitin, one of the most abundant carbohydrates in the natural world. Chitin is also found in the exoskeletons of crustaceans and arthropods (and is a component of bacterial cell walls). Fungi are most often found as asexual hyphal structures that form fruiting bodies (like mushrooms, truffles, and the puffball above) during sexual reproduction. Fungi can be yeasts-single celled, or molds-strands of hyphae that form a mycelium which can be septate (have walled divisions along the hyphae) or aseptate. Some fungi are dimorphic and have both a yeast and a mold stage. You will observe both in this lab.

    Fungi form both asexual and sexual spores, in groups that reproduce via both methods. Asexual spores come in a huge variety of types and their structures are often used to identify them. In this lab you will observe two of the most common types of asexual spores. Rhizopus and other fungi in the group Zygomycota produce sporangiospores inside a sporangium. The sporangium is produced at the end of a stalk originating in the hyphal filaments (Fig. 1). Penicillium and Aspergillus, both in the group Ascomycota, produce asexual spores called conidia that are borne naked on a stalk (Figs. 2 and 3). Fungi in the group Basidiomycota do not appear to reproduce asexually.

    Table \(\PageIndex{1}\): Types of Fungi
    Figure #

    Photos:

    Take notes on labeled diagrams here:

    1

    clipboard_eb4c7fdef9977ebe9581fdbd1e1de807e.png

    Rhizopus sporangia

    By Curtis Clark (Own work) CC BY-SA 3.0

    2

    clipboard_e1bbf5b741c6964b7210b2b96aecb8262.png

    Aspergillus sporangia

    K.C. Burke CC BY-NC SA 4.0

    3

    clipboard_e2193b8a70da61cf60c35c2b515ab07c7.png

    Penicillium sporangia

    K.C. Burke CC BY-NC SA 4.0

    Sexual spores of Zygomycota are called zygospores, and it follows that Ascomycota produce sexual spores called ascospores and Basidiomycota produce sexual spores called basidiospores. Sexual reproduction occurs when hyphae of opposite mating types fuse and fertilization occurs. Zygospores are a single spore from fused hyphae. Ascopores and basidiospores are produced inside segments of hyphal filaments that have formed a fruiting body. You will see prepared slides of each type.

    4

    clipboard_e5d656d21f1ae438c4a8176386f02e411.png

    Rhizopus zygospore

    Curtis Clark CC BY-SA 3.0

    5

    clipboard_ed7bf64ed540877ae8b4b27e917b3981f.png

    Ascospores (Morchella)

    By Jon Houseman CC BY-SA 3.0

    6

    clipboard_e990cc9de2151112466044b72f053a814.png

    Basidiospores (Coprinus)

    By Jon Houseman CC BY-SA 3.0

    7

    clipboard_e9765261c72843da5e079b232db981826.png

    Yeast cells, Candida albicans

    Public Domain (Pinoche)

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