state while the reproductive state is the fruiting body state. There are cases where the vegetative state can be quite large—in one case, a single organism covers more than 2,000 acres of hyphae. Fungi are considered heterotrophs that live off of other organic compounds. Many are saprophytic, meaning they live off of dead or dying organisms. They don’t fix carbon dioxide in photosynthesis and they don’t fix nitrogen from the atmosphere. They do not ingest and then digest, like animals and many other organisms. Instead, they do the opposite. They send out exoenzymes outside of the hyphae that process the food outside of the organism. Then they absorb the smaller molecules. These exoenzymes will be able to break down the cellulose and lignan of plant cells. Similar to animals, their storage molecule is glycogen rather than starch.
FUNGAL REPRODUCTION There are many ways that fungi can reproduce asexually, including budding, fragmentation, and spore formation. Sexual reproduction can also occur. The so-called perfect fungi can reproduce both sexually and asexually, while the “imperfect fungi” can only reproduce through mitosis. They do not undergo binary fission. Spores can be produced and can be dispersed through other animals or the wind. These spores tend to be lighter and much smaller than plant seeds with trillions of spores released at one time in certain species. This huge number of spores will ensure that some of them will find the right habitat in order to start hyphal growth again. Asexual fungal reproduction can be through budding, spore formation, or fragmentation. Fragmentation involves the breaking off of a hypha from the main mycelium. Yeast cells will bud off in a sort of cytokinesis process with mitosis occurring to send a copy of the genome to the daughter cell. The most common asexual reproductive strategy is through spore formation. One parent will make spores that will be genetically identical to the parent organism. The spores can be released from the parent thallus or can make a sporangium, which is a special reproductive sac. Figure 47 shows the fungi life cycle:
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