What are fungi? Heterotrophs that secrete digestive enzymes on organic matter and absorb released nutrients –Saprobes feed on organic remains (major decomposers in ecosystems) –Symbionts, harmless or beneficial –Parasites Include single-celled yeasts and large multicelled species

Fungal Groups Three major groups –Zygote fungi –molds that grow on foods (fruits, breads) –few species are dangerous pathogens –sac fungi, –most diverse group –single-celled yeasts and multicelled species –club fungi –Multicelled club fungi also have hyphae (mushrooms) are major decomposers in forest habitats

Fungal Life Cycles Sexual and asexual spore production In multicelled species –Spores germinate, give rise to filaments (hyphae) –Filaments grow into extensive mesh (mycelium) Sexual reproduction –Hyphae form short-lived, spore- producing reproductive structures (mushrooms)

What are lichen? A composite organism that consists of a fungal symbiont and one or more photoautotrophs (green algae or cyanobacteria) The fungus makes up most of the lichen, and obtains nutrients from its photosynthetic partner

Mycorrhizae (Fungus-Roots) Symbiotic interaction between fungus and plant Fungal hyphae surround or penetrate roots and supplement their absorptive surface area Fungus shares some absorbed mineral ions with the plant, gets some carbohydrates back

Fungal Infections A number of pathogenic fungi can destroy crops, spoil food, and cause diseases in humans –Examples: Athlete’s foot, apple scab, ergot