Fungi

1. Fungi Fungi are eukaryotic heterotrophs that have cell walls. The cell wall is made of chitin, a complex carbohydrate found in the external skeleton of insects. Fungi unlike animals do not ingest their food. They digest the food outside of their body then absorb it. They absorb the nutrients from decaying organic matter. Other fungi are parasites.

2. Structure and Function of Fungi Except for Yeast, all fungi are multicellular. Hyphae is a multicellular fungi composed of thin filaments. Each hyphae is one cell thick. Cross walls divide hyphae into cells that contain 1-2 nuclei. The cross walls have tiny openings through which cytoplasm and nuclei can move. Other hyphae lack cross walls and contain many nuclei.

4. Structure and Function of Fungi The bodies of multicellular fungi are composed of many hyphae tangled together into a thick mass called mycelium. The mycelium is well suited to absorb food because it permits a large surface area to come in contact with food sources. Fruiting body is the reproductive structure growing from the mycelium in the soil beneath it. Clusters of mushrooms are part of the same mycelium which means they are part of the same organism

5. Structure and Function of Fungi As time passes, the nutrients in the soil near the center of the mycelium are depleted so the mushroom will only sprout at the edges of the mycelium forming the “fairies dancing in circles”.

6. Reproduction in Fungi Most fungi reproduce asexually and sexually. In asexual reproduction, the cells or hyphae breaks off from the fungus and begin to grow on their own. Some fungi produce spores which scatter and grow into new organisms. Spore reproduce by mitosis. Sporangia are structures which produce the spores. They are at the tip of specialize hyphae called sporanophores.

7. Reproduction of Fungi

8. Sexual Reproduction of Fungi The sexual reproduction of fungi involves 2 different mating types. Gametes of both mating types are about the same size, they are not called female and male. The mating types are (+) and (-). When the hyphae of opposite type meet, they start sexual reproduction by fusing by bringing (+) and (-) nuclei together in the same cell. After a period of growth and development the nuclei form a diploid zygote nucleus and enters meiosis.

9. Structure and Function of Fungi The spores are capable of growing by repeated rounds of mitosis into a new organism.

10. How Fungi Spread Many fungi produce dry almost weightless spores. These spores scatter easily in the wind. The spores will germinate if they land in a favorable environment with the proper combination of temperature, moisture, and food so that the spores can grow. The probability that a spore will produce a mature organism can be less than one in a billion.

11. How Fungi Spread Other fungi are specialized to lure animals. Stinkhorns smell like rotting meat which attracts flies. When the fly lands on the stinkhorn the fly will ingest the sticky smelly fluid on the surface of the fungus. The spore containing fluid will pass unharmed out of the fly’s digestive system, depositing spores over many kilometers.

12. Classification of Fungi Fungi is classified according to their structure and method of reproduction. Four Main Groups of Fungi • Common Mold - Zygomycota • Sac Fungi - Ascomycota • Club Fungi - Basidiomycota • Imperfect Fungi - Deuteromycota

13. Common Mold The common mold grows on meat, cheese and bread. They are in the phylum Zygomycota called zygomycetes. Their life cycle includes zygospores. Zygospore is a resting spore that contains zygotes which formed during sexual phase of the mold life cycle.

14. Structure and Function of Bread Mold Black bread mold Rhizopusstolonifer is dark and fuzzy. 2 different kinds of hyphae • Rhizoids is rootlike hyphae that penetrate the bread surface. It anchors the fungus to the bread, release digestive enzymes, and absorb digestive organic material. • Stolons is stemlike hyphae which run along the surface of bread. Sporangiophores has hyphae that push up into the air. The sporangia form at its tips.

15. Life cycle of Molds Sexual phase begins when hyphae from different mating types fuse to produce gamete for structures called gametangia. Gametes of the opposite mating type form diploid (2N) zygotes. The zygotes develop into thick walled zygospores which may remain dormant for months. When the conditions become favorable, the zygospore will germinate then undergo meiosis. New haploid spores are released. The signifigance of this sexual process it the zygote formation is followed by meiosis.

16. Sac Fungi Sac Fungi belongs to the phylum Ascomycota. Ascomycetes is the name for the ascus, a reproductive structure that contains spores. Life Cycle of Sac Fungi includes asexual and sexual. Asexual Reproduction – tiny spores called Conidia formed at the tips of the specialized hyphae called conidiophores. If the spores land in a suitable environment it will grow into a haploid mycelium.

17. Sac Fungi Sexual Reproduction occurs when the haploid hyphae of 2 different mating types grow close together. The hyphae produce a fruiting body and sexual reproduction continues. Ascus forms with the fruiting body. Within the ascus, the 2 nuclei of different mating type fuse together for a diploid zygote. The zygote divides by meiosis producing 4 haploid cells. Meiosis is followed by a cycle of mitosis then 8 cells are produced (Ascospores). Ascospores germinate and grow into a haploid mycelium.

18. Yeast Yeast is unicellular fungi. Yeast is classified as ascomycetes because they form asci wit ascospores during the sexual phase of their life cycle. Budding is the process of asexual reproduction in yeast. Ascospores become active in a moist environment. Producing the byproducts of alcoholic fermentation carbon dioxide and alcohol. The carbon dioxide makes beverages bubble and bread rise.

19. Club Fungi The phylum for Club Fungi is Basidiomycota name from a specialize reproductive structure that resembles a club. Basidium is a spore bearing structure. Basidia if found on the gills that grow on the underside of a mushroom caps. Life Cycle of the Club Fungi Basidiospores germinate to produce a haploid primary mycelium which begins to grow. A secondary mycelium is produced. Spores producing fruiting bodies push above the ground. Fruiting bodies are mushrooms. Each mushroom begins as a mass of growing hyphae that forms a button or thick bulge at the soil’s surface.

20. Club Fungi Fruiting bodies expand with astonishing speed producing fully developed mushrooms overnight. The remarkable growth is caused by cell enlargement, not cell division. The cells of the hyphae enlarge by rapidly taking in water. Each gill is lined with basidia.

21. Imperfect Fungi The imperfect fungi belongs to the phylum Deuteromycota. This fungi is not place in other phyla because researchers have never been able to observe a sexual phase in the life cycle. Imperfect fungi is closely resembles ascomycetes. The most known genera of this group is Penicillium. It grows on fruit and is the source of antibiotic penicillin. Penicillin evolved from an ascomycota that lost the sexual phase of its life cycle.