Kingdom Fungi

1.         General

            a.         Although originally classified as plants because they share some characteristics, fungi have several characteristics that make them different:

                        i.         They lack chlorophyll so they are not photosynthetic.

                        ii.        The cell wall is made of chitin rather than cellulose.

                        iii.       Fungi are heterotrophs and absorb food after secretion of enzymes and extracellular digestion while plants are photosynthetic.

                        iv.       Fungi reproduce by spores rather than seeds.

                        v.         Fungi are composed of filaments called hyphae. Hyphae may be branched. A dense mass of hyphae is called a mycelium.

                                    (1)       Hyphae may contain internal crosswalls that divide the hyphae into separate cells. The crosswalls of many species have pores, allowing cytoplasm to flow freely from one cell to the next. Cytoplasmic movement within the hypha provides a means to transport materials throughout the hyphae.

            b.         Humans use fungi in a variety of ways:

                        i.         Many are harmful and cause decay, rot and spoilage.

                        ii.        Some cause serious plant and animal diseases.

                        iii.       Many are beneficial.

                                    (1)       Yeasts are used in the manufacture of bread, wine and beer.

                                    (2)       Production of penicillin.

                                    (3)       Many mushrooms are eaten as food.

2.         Nutrition

            a.         Fungi are major decomposers in every ecosystem. They break down matter into simple nutrients that can be used by other organisms.

            b.         All are heterotrophic. Fungi excrete enzymes into their environment to digest food. They then absorb the nutrients.

            c.         Most species of fungi decompose dead matter. Many are parasitic and obtain nutrients from living organisms.

3.         Reproduction

            a.         Most fungi reproduce sexually although there are a few examples of those that reproduce asexually. Yeast are a notable exception as they show mostly asexual reproduction.

            b.         The hyphae of two individuals meet and fuse. The resulting fungus then contains DNA from each of the two partners.

            c.         The above ground structure that we call a mushroom is actually the reproductive structures of the fungus. Spores produced in the mushroom are dispersed and grow into new individuals. Spores are non-motile, unlike the gametes of plants and animals.

            d.         Spores are dispersed over great distances by wind, insects, and animals.