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Biology 2014-2015

Ecology of Fungi

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Section 21-3

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Athlete's Foot

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Ringworm

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Wheat Rust

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Corn Smut

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    

    Plants provide the fungi with the products of photosynthesis