Investigating Fungi: Mold and Yeast

Fungi• Fungi are in their own kingdom.– They do not capture their own food like animals and

cannot make their own food like plants.• May be unicellular or multicellular. Can be

microscopic or very large.• One common species of fungi is black bread

mold that grows on bread, fruit, and other foods.• Other fungi include mushrooms, puffballs, yeast,

lichen, and most mildew.

Fungi Anatomy• Structures that help fungi absorb and digest food:– Hyphae: the body of a typical fungus, consisting of

many tiny tubes– Mycelium: hyphae tangled into a thick mass

• Fungi live on top of their food source. The mycelium grows and covers the food.

• Fungi release juice that breaks down the plant/animal matter.

• Hyphae absorb this matter.

Fungi Reproduction• The most visible part of a fungus is its

reproductive structure.– For example, a mushroom’s mycelium grows below

ground, but its reproductive structure (umbrella-shaped cap) is above ground.

• Fungi spores are like plant seeds.– Spores are produced inside the mushroom’s cap.– Spores are released and float away.– When the spores land in a place with the right

temperatures, food, and moisture, they germinate and grow.

Bread Mold

• Bread mold spores travel in the air.• The spores land on a piece of moist bread and

it grows specialized hyphae called rhizoids.• Rhizoids travel below the surface of the bread

and help anchor the mold like plant roots.• Some hyphae spread along the surface and

form a mycelium. Stolons (another kind of specialized hyphae) develop from the mycelium.

Bread Mold Continued

• From the stolons, stalks grow upward and round reproductive structures called sporangia form at the top.

• New spores form inside the sporangia.• Sporangia gives bread mold its black color.

DRAW DIAGRAM ON THE BOARD.

Relationships

1. Symbiotic – relationship between two organisms in which both organisms benefit.

Example: Leaf cutter ants help the fungi by spreading its spore and the leaf cutter ant benefits by eating the fungi that is created from the spores.2. Parasitic – obtaining nutrition from living on or in

another organism.Example: One type of fungus feeds on elm trees causing Dutch Elm Disease and has killed millions of elm trees.

The Good Side of Fungi

• Fungi are decomposers. Decomposers break down plant/animal remains and release the nutrients back to the earth.

• Some fungi are used to make antibiotics.• Some ripen cheese.

YeastKingdom: FungiPhylum: Ascomycetes• Yeast are unicellular and microscopic.• Dry granules of yeast contain tiny spore sacs.• In a moist, warm environment where a food source

is available, the spores become active and the yeast cells reproduce.

• Yeast cells reproduce mostly by budding.• When yeast cells become active and feed they

undergo a process called fermentation.

Inside Us• The oily surfaces of our noses, ears, and scalps

and our mouths and intestinal tracts are places where yeast cells live on humans.

• Most of the time the yeast population in our bodies causes no problem, but taking certain medications or changing our diet could cause yeast to multiple rapidly.– Thrush: infection that occurs in the lining of our

mouths when yeast cells overgrow (most often found in babies and children)

Food and Drink

• In a warm and moist environment, yeast cells cause bread dough to rise. They do this through respiration and fermentation.– Fermentation: Yeast cells feed on the dough,

reproduce and excrete carbon dioxide and alcohol– Respiration: Yeast consume the alcohol they’ve

made using oxygen to break it down and turn its energy into fuel for growth and reproduction

• The carbon dioxide produced by the yeast accumulates in the bread and makes it rise. When to bread is baked you can see little holes where the carbon dioxide bubbles have been.

• The same yeast that is used in breadmaking is also used in beer brewing.