All Fungi Are Heterotrophic

§    Fungi cannot manufacture their own food

§    Must rely on other organisms for energy

►        saprobes, organisms that obtain food from decaying organic matter

►        parasites, which harm other organisms while living directly on or within them

►        symbionts that live in close and mutually beneficial association with other species

Fungi as Decomposers

§    Maintain equilibrium by recycling nutrients by breaking down the bodies and wastes of other organisms

§    Feed by releasing digestive enzymes that break down leaves, fruit, and other organic material into simple molecules

Fungi as Parasites

Plant Diseases

§    Fungi can cause disease such as corn smut, which destroys the corn kernels

§    Mildews, which infect a wide variety of fruits, are also fungal

§    Responsible for the loss of approx. 15% of the crops grown in temperate regions

§    Responsible for the loss of approx. 50% of the crops in tropical areas

v    Example - wheat rust affects one of the most important crops grown in North America

w   Rusts are caused by a type of basidiomycete that needs two different plants to complete its life cycle.

w   Barberry plants produce the spores that are carried by wind to wheat plants.

w   Spores germinate and infect wheat plants.

w   This rust produces a second type of spore that infects other wheat plants spreading like wildfire.

w   Tough black spores are produced late in the season and survive over winter.

w   In spring, they go through a sexual phase, produce spores that infect barberry plants.

v    Understanding the life cycle helps to slow the spread by destroying the barberry plants

Human Diseases

§    Athlete's foot is caused by a deuteromycetes infecting the toe area producing a red, inflamed sore from which spores are released and can spread from person to person

§    This same fungus infects other areas, such as the skin of the scalp, producing a red scaling sore known as ringworm

§    Candida albicans, a yeast, may produce thrush, a painful mouth infection or infections of the female reproductive tract.

Other Animal Diseases

§    Cordyceps is a fungus that infects grasshoppers in rain forests of Costa Rica.

§    Microscopic spores become lodged in the grasshopper and produce enzymes that slowly penetrate the insect's tough external skeleton.

§    Spores multiply in the insect's body, digesting all its cells and tissues until the insect dies.

Symbiotic Relationships

§    Some fungi form a symbiotic relationship in which both partners benefit.

Lichens

§    Lichens are not a single organism but rather a symbiotic association between a fungus and a photosynthetic organism.

§    Fungi in lichens are usually ascomycetes or basidiomycetes

§    Photosynthetic organisms are either green algae or a cyanobacterium, or both

§    Extremely resistant to drought and cold.

§    Grow in places where few other organisms can survive--dry, bare rock in deserts and on the tops of mountains.

§    Algae or cyanobacteria carry out photosynthesis providing the fungus with energy

§    Fungus provides algae or bacteria with water and minerals collected from the sunlight

§    Lichens are also sensitive to air pollution, and are among the first organisms to be affected when air quality deteriorates.

Mycorrhizae

§    Mycorrhizae is a mutualist association between plant roots and fungi.

§    80% of all plant species form mycorrhizae with fungi

§    Tiny hyphae of the fungi aid plants in absorbing water and minerals by increasing the surface area of the root system