Most fungi reproduce both sexually and asexually. Unlike most eukaryotes, most fungi are haploid throughout most of their life cycle.

Asexual Reproduction

Asexually, fungi produce thousands of genetically identical haploid spores, usually on modified cells of the hyphae. When these spores are placed in favorable environmental conditions, they germinate and grow new hyphae, each of which can form a mycelium and produce thousands of new asexual spores.

A variety of asexual spores are formed by different fungi. For example, sporangiophores (spoh-RAN-jee-oh-FAWHRZ) are specialized hyphae that look like upright stalks. On top of a sporangiophore is a sac called a sporangium (spoh-RAN-jee-UHM). Inside each sporangium, spores called sporangiospores (spoh-RAN-jee-oh-SPOHRZ) are made. Rhizopus, the black mycelial fungus that is commonly found growing on bread, is a sporangiospore-forming fungus.

Other fungi form spores called conidia (koh-NID-ee-uh) (singular, conidium), which are formed without the protection of a sac. Conidia are formed on top of a stalklike structure called a conidiophore (koh-NID-ee-uh-FAWHR). Penicillium, which is used to produce penicillin and certain types of cheeses, is a fungus that reproduces asexually by means of conidia.

Asexual reproduction may also occur by fragmentation. In this process, a septate hypha dries and shatters, releasing individual cells that act as spores. The fungus that causes athlete's foot reproduces this way. Yeasts reproduce by a process called budding, shown in Figure 26-3. Budding is an asexual process in which part of a yeast cell pinches itself off to produce a small offspring cell.

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