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