Fungi

1. Fungi Chapter 30

2. Shared Characteristics • Distinctive fungal features • Fungi are heterotrophs. • Fungi have several cell types. • Some fungi have a dikaryon stage. • Fungi have cell walls that include chitin. • Fungi undergo nuclear mitosis.

3. The Body of a Fungus • Fungi exist mainly in the form of slender filaments (hyphae). • mycelium - mass of connected hyphae • grows through and penetrates substrate

4. The Body of a Fungus • Fungi cell walls are formed of polysaccharides and chitin. • Mitosis is unique. • nuclear envelope does not break down and re-form spindle apparatus formed within

5. How Fungi Reproduce • Differ from most animals and plants in that each compartment of hypha can contain one, monokaryotic two dikaryotic or more nuclei • Many nuclei intermingle in cytoplasm of fungal mycelium which can lack distinct cells • heterokaryotic – nuclei from genetically distinct individuals • homokaryotic – hyphae whose nuclei are genetically similar to one another

6. How Fungi Reproduce • Fungi are capable of both sexual and asexual reproduction. • Fungi reproduce sexually after two hyphae of opposite mating type fuse. • in some fungi fusion two haploid cells immediately results in diploid cell (2n)

7. How Fungi Reproduce • Spores most common means of reproduction • may form from asexual or sexual processes • most often dispersed by wind but some spread by insects or other small animals

8. How Fungi Obtain Nutrients • All fungi obtain food by secreting digestive enzymes (exoenzymes) • absorb the organic molecules produced (external digestion). • hyphae network SA for absorption • many fungi able to break down cellulose in wood

9. Anaerobic fermentation provides flavor for wine and cheese. • Fungi are decomposers • Fungi often act as disease-causing organisms for both plants and animals.

10. Ecology of Fungi • Mutualistic associations • lichens - fungi and green algae • mycorrhizae - fungi and plant roots

11. Four Major Groups of Fungi • Four major groups • Chytridiomycota • Zygomycota • Basidiomycota • Ascomycota

12. Chytridiomycota • aquatic, flagellated fungi • most closely related to ancestral fungi

13. Zygomycota • includes common bread molds • hyphae produce clumps of erect stalks - sporangiophores form sporangia

14. Basidiomycota • Most familiar fungi (mushrooms, toadstools, puffballs, rusts, and smuts) • named for characteristic sexual reproductive structure, basidium

15. Ascomycota • Very large group including yeasts, common molds, and morels • Named for reproductive structure ascus

16. Ascomycota • Yeasts • unicellular - most reproduction is asexual and takes place by cell fission or budding • ferment carbohydrates • play a leading role in genetic research

17. Lichens • Lichens are symbiotic associations between a fungus and a photosynthetic partner. • fungal hyphae penetrate photosynthetic cells and transfer nutrients to fungal partner.

18. Mycorrhizae • Roots of about 90% of all kinds of vascular plants are involved in mutualistic symbiotic relationships (mycorrhizae).

19. Mutualistic Animal Symbioses • A range of mutualistic fungal-animal symbioses has been identified. • ruminants • leaf-cutter ants

20. Fungal Parasites and Pathogens • Aflatoxins - carcinogenic compounds produced by strains of Aspergillus flavus • grows on corn, peanuts, cotton seeds