How are fungal spores dispersed?

Spore dispersal is most commonly carried out by the wind. Spores are both tiny and lightweight; as such, they can travel through the air for many miles. Spores are also scattered by falling rain.

What are sclerotia?

Sclerotia are the aggregate of hyphae enclosed in thick walls that form a protective covering when conditions (temperature and water) are not conducive for growth. When conditions improve, the sclerotia germinate and produce stalks containing spore-bearing bodies. Ascospores are embedded in the tips of the stalks. When transported by wind, ascospores may land on grasses or grains, especially rye. The sclerotia continue to grow after they have landed on the host plants.

What are dimorphic fungi?

Many fungi, particularly those that cause disease in humans, are dimorphic—that is, they have two forms. In response to changes in temperature, nutrients, or other environmental factors, they can change from a yeast form to a mold form fungi.

How do fungi reproduce?

Fungal reproduction occurs in two different ways—sexually or asexually. Asexual reproduction occurs through fission, budding, or—most commonly—by spore formation. Sexual reproduction occurs by means that are characteristic for each group. Two types of reproductive structures are found in fungi. Sporangia produce spores, whereas gametangia produce gametes. In order to sexually reproduce, fungi often carry out some type of conjuga- tion. Hyphae of two genetically different mating types come together and fuse, forming a diploid zygote. Most fungi reproduce sexually with nuclear exchange rather than gametes.

Do fungi exhibit an alternation of generations similar to plants?

Organisms with life cycles that exhibit an alternation of generations have both a haploid phase and a diploid phase. During the haploid phase, reproduction is conducted through gametes, which fuse together to form a zygote. During the diploid phase, reproduction is conducted by spores. Spores develop individually and divide through mitosis, producing the gametophytes of the next generation. Because fungi have both a haploid and diploid phase, they exhibit an alternation of generations.

What is the life cycle of a typical fungus such as the black bread mold, Rhizopus nigricans?

The life cycle of black bread mold, Rhizopus nigricans, is characteristic of the members of the phylum Zygomycota. This fungus has a period of sexual reproduction and a period of asexual reproduction that occurs more frequently. During sexual reproduction, there is a fusion of gametangia. The resulting zygosporangium forms a thick coat that awaits favorable conditions in order to conduct further development. When conditions are favorable, the zygosporangium germinates into a sporangium. During asexual reproduction, spores are produced in the sporangium and then dispersed.

What is the dikaryotic phase of fungal life cycles?

The dikaryotic phase of the fungal life cycle is unique. During this unusual phase, which is common in many species of fungi, cells contain two distinct nuclei. These two nuclei divide simultaneously as the mycelium grows; growth continues until fusion occurs during karyogamy.