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