21-1 The Kingdom Fungi
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21-1 The Kingdom Fungi
What Are Fungi?
What Are Fungi?
Fungi are eukaryotic heterotrophs that have cell walls.
Their cell walls contain chitin, a complex carbohydrate
also found in the exoskeletons of insects.
Fungi digest food outside their bodies and absorb it.
Some fungi absorb nutrients from decaying matter in
soil.
Other fungi are parasites, absorbing nutrients from their
hosts.
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21-1 The Kingdom Fungi
Structure and Function of Fungi
Structure and Function of Fungi
Except for yeasts, all fungi are multicellular.
Fungi are made up of thin filaments called hyphae.
Each hypha is only one cell thick.
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21-1 The Kingdom Fungi
Structure and Function of Fungi
In some fungi,
cross walls divide
hyphae into cells
with 1 or 2 nuclei.
In the cross walls,
there are openings
through which the
cytoplasm and
nuclei can move.
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21-1 The Kingdom Fungi
Structure and Function of Fungi
Some hyphae lack cross walls and contain many
nuclei.
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21-1 The Kingdom Fungi
Structure and Function of Fungi
Fungus Structure
The bodies of multicellular fungi are composed of
many hyphae tangled together into a thick mass
called a mycelium.
The mycelium permits a large surface area to come in
contact with the food source through which it grows.
A fruiting body is a reproductive structure growing
from the mycelium in the soil beneath it.
A mushroom is the fruiting body of a fungus. Clusters
of mushrooms are often part of the same mycelium,
so they are part of the same organism.
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21-1 The Kingdom Fungi
Structure and Function of Fungi
Fairy Rings
Mycelia can live for many years.
Through time, soil nutrients near the center of the
mycelium become depleted.
Mushrooms will sprout only at the edges of the
mycelium, producing a ring.
People once thought that fairies dancing in circles
produced these rings so they were called “fairy rings.”
Over many years, fairy rings and grow to be 10-30
meters in diameter.
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21-1 The Kingdom Fungi
Structure and Function of Fungi
Structure of a Typical Fungus
Hyphae
Fruiting
body
Mycelium
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21-1 The Kingdom Fungi
Reproduction in Fungi
Reproduction in Fungi
Most fungi reproduce both asexually and sexually.
Asexual reproduction occurs when hyphae break off
and begin to grow on their own.
Some fungi produce spores, which scatter and grow.
Spores are reproductive cells that are capable of
growing into a new organism by mitosis alone.
In some fungi, spores are produced in structures
called sporangia.
Sporangia are at tips of specialized hyphae called
sporangiophores.
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21-1 The Kingdom Fungi
Reproduction in Fungi
Sexual reproduction has two mating types: + and Because gametes of both mating types are about the
same size, they are not called male and female.
Hyphae of opposite mating types meet and fuse,
bringing “+” and “–” nuclei together in one cell.
After growth and development, the nuclei form a diploid
zygote nucleus.
The zygote enters meiosis and produces haploid spores.
Spores are capable of growing into new organisms.
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21-1 The Kingdom Fungi
How Fungi Spread
How Fungi Spread
Many fungi produce dry spores that scatter easily in
the wind.
If these spores are to germinate, they must land in an
environment with the proper combination of
temperature, moisture, and food so they can grow.
Under the best circumstances, the probability that a
spore will produce a mature organism is one in a
billion.
Other fungi are specialized to lure animals, which
disperse spores over long distances.
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