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CHAP. 3.3 – KINGDOM: FUNGI
I. WHAT ARE FUNGI?
You have seen fungi when you observed mold on
bread or decaying fruit, mushrooms sprouting out of
the grass, and in the grout of bathroom tiles.
Characteristics of Fungi:
1. Fungi are eukaryotes (they have a nucleus).
2. Fungi reproduce by spores.
3. Fungi are Heterotrophs (does not make their own
food).
4. Grow when the environment is moist, warm, and
damp.
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II. CELL STRUCTURE
Fungi cells are arranged in structures called hyphae
(the exception to this is yeast cells).
Hyphae are branching, threadlike tubes made of
cytoplasm.
Hyphae are arranged in two ways and the arrangement
will decide the appearance of the fungi:
1. Loosely – tangled: Hyphae will spread across a
surface like a web. This structure is the fuzz growing
on top of old food.
2. Tightly – packed: Hyphae that is tightly wound
together that it forms a solid mass. It forms the stalk
and cap of mushrooms.
III. HOW DO FUNGI OBTAIN FOOD?
First, the fungus grows hyphae unto a food source.
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Second, digestive chemicals ooze from the tips of the
hyphae into the food.
Third, the digestive chemicals break down the food into
small substances.
Fourth, the small substances are absorbed through
hyphae.
Fungi feed off of dead organisms (such as fallen leaves)
and living organisms (such as human skin in athlete’s
foot).
IV. REPRODUCTION IN FUNGI
A. ASEXUAL REPRODUCTION
Fungi can asexually reproduce in two ways:
making spores or budding.
1. Spores
The usual way fungi reproduce is making thousands of
spores.
The spores are lightweight and surrounded by a
protective covering.
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Being lightweight, spores are easily carried by air and
water.
If the spore lands in a place that is moist, warm, and
damp, it will grow.
The spores are produced in a fungi structure called a
fruiting body. The fruiting body is nothing more than
a reproductive hyphae.
2. Budding
Only unicellular fungi like yeast reproduce by budding.
In budding, a new cell forms inside a parent cell. The
new cell eventually makes it way out of the parent cell
and lives on its own. The new cell is identical to the
parent cell.
B. SEXUAL REPRODUCTION
Fungi only undergo sexual reproduction when growing
conditions become unfavorable.
In sexual reproduction, hyphae of two different fungi
meet and exchange genetic material.
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A new spore-producing structure grows from the
joined hyphae. This new spore-producing structure
makes spores that will develop into fungi.
V. CLASSIFICATION OF FUNGI
Fungi are classified according to 1) shape of their
spore-producing structure and 2) on their ability to
reproduce.
There are four groups of fungi:
1. threadlike fungi – Fungi are produced by spores in
their threadlike hyphae (ex. Bread mold).
2. sac fungi – Fungi produce spores in structures that
look like sacs (ex. Yeast).
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3. club fungi – Fungi produce spores that look like clubs
(ex. Mushrooms).
4. imperfect fungi – Fungi in this group will not
reproduce sexually (ex. Penicillium).
VI. FUNGI AND THE LIVING WORLD
A. ENVIRONMENTAL RECYCLING
Fungi are great decomposers. As decomposers, they
break down the chemicals in dead organisms and
return the important nutrients in the chemicals back to
the soil.
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B. FOOD & FUNGI
Yeast helps bread rise and makes wine.
In bread, the yeast is added to the bread dough. The
yeast eats the sugar in the dough and produces carbon
dioxide gas bubbles. The bubbles causes the bread to
rise (you see the bubbles in bread).
Blue cheese is made from a fungus (Penicillium
roqueforti).
C. DISEASE – CAUSING FUNGI
There are many fungi that destroy crops, plants, and
trees. The most famous one is Dutch Elm disease.
The fungi can also attack human skin in the form of
Athlete’s foot and Ringworm.
D. DISEASE – FIGHTING FUNGI
The most important fungus that kills bacteria is
penicillium. It was discovered in 1928 by a Scottish
biologist Alexander Fleming.
Fleming was growing bacteria in Petri dishes and
noticed that a mold grew on some of the dishes. Where
the mold grew, it killed the bacteria and the bacteria
refused to grow near it.
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E. FUNGUS – PLANT ROOT ASSOCIATIONS
Some fungi help plants grow healthier and stronger
such as orchids.
The hyphae of a fungus grow with a plant’s root
system. The hyphae spread out to absorb water and
nutrients for the plant. In return, the fungus eats the
extra food the plant makes.
F. LICHENS
Lichen is a symbiotic relationship between a fungus
and either algae or bacteria. The fungus eats the food
produced from the algae or bacteria. The algae or
bacteria get water and minerals from the fungus.
Lichen is important because:
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1. They are the first organisms to grow on bare rock
after a volcano or fire has occurred. The lichen will
break down the rock into soil for organisms to grow in.
2. They are very sensitive to pollution and will die if it
is present.
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