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Chapter 22 Fungi

Chapter 22 Fungi. Mycology – is the study of fungi Characteristics of Fungi: Fungi are eukaryotic – have membrane enclosed organelles. Fungi are heterotrophic – take in food made by other organisms and lack chlorophyll. They have cell walls made of chitin.

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Chapter 22 Fungi

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  1. Chapter 22 Fungi

  2. Mycology – is the study of fungi Characteristics of Fungi: • Fungi are eukaryotic – have membrane enclosed organelles. • Fungi are heterotrophic – take in food made by other organisms and lack chlorophyll. • They have cell walls made of chitin. • Body structure – consists of tubes called hyphae – form a visible mycelium. • Reproduce asexually and sexually. ,

  3. Parasitic Fungi: • Mostly feed off plants – e.g. potato blight fungus. • Some live on animals – athlete’s foot, ringworm. • Obligate Parasites live on live hosts – do not kill host e.g. mildews, smuts. • Facultative parasites – may kill host e.g. fungi causing soft rot in fruit.

  4. Saprophytic Fungi: • Feed off dead plants and animals and cause decay – e.g. mushrooms and mould. • in the environment.

  5. Edible Field Mushrooms Morels Truffle Poisonous Death Cap Destroying Angels Cordyceps Edible and Poisonous Fungi

  6. Rhizopus

  7. Rhizopus (Bread Mould) • Nutrition in rhizopus • Bread Mould is saprophytic. • It feeds of bread and fruits. • It secretes enzymes which digests the food. • It has rhizoids and hypha that absorb the digested food.

  8. Structure of Rhizopus

  9. Structure of Rhizopus Rhizopus consists of threadlike structures called hyphae and it is a multicellular fungus. Hyphae: digest and absorb the substrate on which they grow. Mycelium: is a mass of hyphae.

  10. Stolon: is a hypha which grows over the surface of the food to allow the fungus to spread more rapidly. Rhizoids: create a larger surface area for the absorption of food. Sporangiophore: supports the sporangium and allows the spores to be more easily dispersed.

  11. Life Cycle of Rhizopus • Asexual Reproduction: • Hyphae grow upwards to form sporangiophores the tip of which swells to produce the sporangium. • Sporangium divides by mitosis to produce cells. • Each cell develops a wall and is now called a spore.

  12. The sporangium cracks in the wind. • Spores are dispersed. • If they fall on suitable substrate they grow into new hypha and mycelium.

  13. RHIZOPUS– Asexual Reproduction

  14. Sexual Reproduction Rhizopus exists as two separate strains called plus and minus strains. + Strain - Strain Sexual reproduction in Rhizopus can only occur between a plus and a minus strain.

  15. + Strain - Strain When hyphae from opposite strains grow close together swellings grow on both strains and touch each other.

  16. + Strain - Strain Nuclei from both hyphae move into these swellings which are now called progametangia.

  17. + Strain - Strain Cross-walls form to produce gametangia.

  18. + Strain - Strain The walls of the gametangia dissolve and a number of fertilisations take place producing diploid zygote nuclei.

  19. + Strain - Strain A zygospore forms around these nuclei. When conditions are suitable the zygospore germinates by meiosis.

  20. A hypha grows out of the zygospore and produces a sporangium at the tip. The sporangium opens releasing many haploid spores which grow into new individuals.

  21. Saccharomyces (Yeast) • Structure of Yeast • It is a unicellular fungus. • Yeast cells are round or oval. • Yeast cells have thin walls made of chitin. • Yeast cells have a thick granular cytoplasm.

  22. Usually one large vacuole present. • Each cell has one nucleus. • Yeasts respire anaerobically: Glucose → 2 ethanol + 2 carbon dioxide.

  23. Reproduction in Yeast • Reproduction in yeast is asexual by a process called budding. • Budding: • A small bud forms at the side of the cell. • The nucleus divides by mitosis. • One of the new nuclei enters the bud.

  24. 4)The bud fills with cytoplasm 5) a) The bud can remain attached and form a colony. b) OR the bud can break free and form its own colony. N.B.: Please know and be familiar with the diagrams illustrating the process of budding

  25. Asexual Reproduction in Yeast

  26. Benefits Yeast – used to produce alcohol. Penicillium – used to produce antibiotic penicillin. Puffball Mushroom – is a food (edible). Disadvantages They destroy food, crops and a wide range of other materials: - Rhizopus stolonifer – causes bread mould. Fungal diseases of plants, humans and animals can result in financial losses. Death Cap Mushroom – poisonous if eaten. Economic Importance of Fungi(Must know two benefits and two disadvantages)

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