21.4 - Fungi

Fungi and You

Believe it or not, fungi play an important role inyour life. The bread you eat, the salad you make,

and the medicine that you take when you aresick may include various types of fungi or

products made from fungi.

1. List as many examples of fungi that you can.2. How are fungi helpful to humans?3. How are fungi harmful to humans?

What Are Fungi?Types: mushrooms, mold, yeast, mildew, truffles

Basic characteristics:• Heterotrophic eukaryotes • Many feed by absorbing nutrients from

decaying matter• Others live as parasites absorb nutrients from

their hosts

What Are Fungi?• Cell walls made of chitin (polymer of modified

sugars, also found in arthropod exoskeletons)– Evidence that fungi are more closely related to

animals than plants• Instead of photosynthesis, fungi produce

enzymes that digest food outside their bodies, then absorb the small molecules released by the enzymes

Structure and Function yeasts – single-celled mushrooms - multi-celled• hyphae - long, slender branching

filaments • mycelium - mass of branching hyphae

below the soil• mushroom fruiting body – reproductive

structure that grows above soil• clusters of mushrooms are often part of

the same mycelium -> same organism

Reproduction• Asexually – release spores that travel through

air/water or break off a hypha• Sexually – transfer of nuclei and cytoplasm

from one hypha to another, then create spores

Diversity of Fungi

• more than 100,000 species of fungi

• major groups differ in their reproductive structures

The Ecology of Fungi1. Decomposition champions help ecosystems by

breaking down dead organisms/recycling essential elements and nutrients

2. Parasitic fungi cause serious diseases in plants and animals

3. Mutualistic associations with photosynthetic organisms in which both partners benefit

Decomposition • Organisms remove

important trace elements and nutrients from the soil

• Fungi release digestive enzymes that break down leaves, fruit, and other organic material into simple molecules

• Fungi then recycles these elements and nutrients

• If not returned, the soil would quickly be depleted

ParasitismPlant Diseases • Parasitic fungi cause diseases that threaten

food crops– ex: mildews infect a wide variety of

plants– ex: corn smut destroys corn kernels

ParasitismAnimal Diseases • Infect insects, frogs, and mammals

- ex: Cordyceps fungus infects grasshoppers in rain forests in Costa RicaGrasshopper eats spores,

germinate and produce enzymes that slowly digest all cells and

tissues until the insect dies, hyphae develop on dead grasshopper and

produce more spores spreading the infection

Human Diseases • Ex: athlete’s foot forms a

mycelium in the outer layers of the skin, which produces a red, inflamed sore from which the spores can easily spread from person to person

• Ex: yeast Candida albicans responsible for vaginal yeast infections and for infections of the mouth called thrush

Symbiotic Mutualism • Lichens - mutualistic association between

fungus + photosynthetic organism- Photosynthetic organism - green alga/ cyanobacterium

• Algae photosynthesize source of energy• Fungus provides water and minerals

                                                                                               

The Lichen is created between the fungus and the alga.

The Lichen is created between the fungus and the alga

Mr. Fungus is ready to greet our friend the alga

Friend alga cell is prepared to greet Mr. Fungus

Lichen =Fungus + photosynthetic organism

Symbiotic Mutualism

• Mycorrhizae – mutualistic relationships between fungus + plant roots- Essential for plant growth

• Fungi hyphae collect water/minerals and bring them to the roots, also release enzymes that free nutrients in the soil

• Plants provide fungi w/ the products of photosynthesis (oxygen and sugar)