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 (umbrellashaped 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.
Yeast
Kingdom: Fungi
Phylum: 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.