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Chapter 27. Fungi

Recommended Article: 【Biology】 Table of Contents for Biology

1. Characteristics

2. Life Cycle

3. Classification

1. Characteristics

⑴ Multicellular and Nonmotile Eukaryotic Organisms

① Exception: Yeast

② Multinucleate fungi → Septa → Multicellular filament

⑵ Lack Chlorophyll, Depend on Heterotrophic Nutrition

① Extracellular Digestion: Absorption through Hyphae

② Symbiosis 1. Ascomycetes: Symbiosis with Lichen (Plants), Cyanobacteria (Bacteria), and Green Algae (Protists)

③ Symbiosis 2. Mycorrhizae: Fungi + Plants (Eukaryotic)

⑶ Composed of Mycelium: Body, Reproductive Structures

① Hypha: Structure formed by elongated cells resembling threads

② A group of hyphae forms a mycelium

⑷ Cell Organelles

① Cell Organelles are enclosed by the Cell Membrane

② Cell Membrane: Composed of Ergosterol

③ Cell Wall: Composed of Chitin, Glucan

⑸ Classification Based on Presence of Septa

① Septa: Walls between cells, containing pores large enough for nuclei to pass through

② Zygomycota, Chytridiomycota: No Septa

③ Ascomycota: Partial Septa

④ Basidiomycota: Septa Present

⑹ Production of Useful Substances like Antibiotics

2. Life Cycle

⑴ 1^st. Hyphae or Mycelium (n)

⑵ 2^nd. (+) Mating Type (n) and (-) Mating Type (n) Fuse to Form Diploid Nucleus (2n)

⑶ 3^rd. Spore (n) Formation

① Zygomycota, Chytridiomycota: Diploid → Fusion → Meiosis

② Ascomycota: Diploid → Cell Division → Fusion → Meiosis, 8 Spores / Ascus

③ Basidiomycota: Diploid → Cell Division → Fusion → Meiosis, 4 Spores / Basidium

⑷ 4^th. Spore (n) Mitosis → Formation of Plasmodium (n)

Figure 1. Life Cycle of Fungi

3. Classification

⑴ Chytridiomycota (Chytrids)

① Earliest Fungi

② Zoospores (Animal-like Spores)

⑵ Zygomycota (Zygomycetes) (e.g., Mucorales)

① No septum

② Sexual Reproduction produces Zygosporangium

③ Zygospore: a spore (n) formed by meiosis of a zygote (2n)

⑶ Mycorrhizae

① Symbiosis with Plants

② Ectomycorrhizae: Observed in 10% of Plants

○ Ectomycorrhizal Hyphae form a tough mantle over the root surface

○ Some Hyphae penetrate the outer cells of the root but do not enter the plant cell walls

③ Endomycorrhizae: Observed in 85% of Plants

○ Endomycorrhizal Hyphae grow into the outer cells of the root and do not form a mantle over the root surface.

○ Some hyphae can grow inward by penetrating the plant cell wall, but they do not break through the cell membrane or enter the cytoplasm.

④ Mycorrhiza → Plant: Mycorrhiza provides Plants with nutrients like NO3- or H2PO4-

⑤ Plant → Mycorrhiza: Plants provide Mycorrhiza with photosynthesis products, such as sugars

⑷ Ascomycota (Sac Fungi) (e.g., Yeasts, Aspergillus oryzae, Penicillium (synthesizing penicilin), Neurospora crassa)

① During sexual reproduction, the ascus, a fruiting body, develops.

② Ascospores: Spores formed within the Ascus (n)

③ Conidiospores: Used during Asexual Reproduction, while Ascospores are used during Sexual Reproduction

④ When survival conditions are unfavorable, yeast cells undergo conjugation to form ascospore.

⑤ Symbiosis with lichen.

⑸ Basidiomycota (Club Fungi) (e.g., mushrooms, cordyceps)

① Hyphae gather to form a fruiting body, and basidiospores are produced in the basidium located in the fruiting body (the mushroom part).

② Basidiospore: a haploid spore (n) formed in the basidium within the fruiting body.

③ Survives by decomposing lignin in wood.

④ A dikaryotic mycelium divides to form mushrooms and basidia.

Input: 2019.03.17 11:00