Lesson 3
Introduction to Fungi
Focus Question
How are fungi classified?
New Vocabulary
chitin
hypha
mycelium
fruiting body
septum
spore
sporangium
Review Vocabulary
decomposer: an organism that feeds on and
breaks down dead organisms, recycling nutrients
back into food webs
Characteristics of Fungi
• Kingdom Fungi contains some of the largest
and oldest organisms on Earth.
• All fungi are eukaryotic heterotrophs.
Characteristics of Fungi
Multicellular Fungi
• Most members of the Kingdom Fungi are
multicellular.
• They appear similar to plants, but they do not
possess chloroplasts or photosynthesize.
Unicellular fungi
• Yeasts are a type of unicellular fungus.
• Useful to humans, though some are
infectious
Major Features in Fungi
Cell Walls
• A difference between plants and fungi is the
composition of their cell walls.
• Plants have cell walls composed of cellulose.
• Fungi have cell walls composed of chitin, a
strong, flexible polysaccharide that is found in
the cell walls of all fungi and in the exoskeletons
of insects and crustaceans.
Major Features in Fungi
Hyphae
• Fungi are composed of long chains of cells called
hyphae.
• Hyphae grow at their tips and branch repeatedly
to form a netlike mass called a mycelium.
• The portion of the fungus above the ground is a
reproductive structure called the fruiting body.
Major Features in Fungi
Cross Walls
• In many fungi, hyphae
are divided into cells by
cross walls called septa
(singular: septum).
• Septa allow nutrients,
cytoplasm, and
organelles to flow
between cells.
• Some fungi are
aseptate, meaning that
they have no septa.
Nutrition in Fungi
• There are three ways in which heterotrophic
fungi get nutrition.
Saprophytic Fungi
• Feed on dead organisms or organic wastes
• Decomposers; recycle nutrients from dead
organisms back into food webs
Nutrition in Fungi
Parasitic Fungi
• Absorb nutrients from the living cells of another
organism, called a host
• Produce specialized hyphae which grow into the
host’s tissues and absorb their nutrients
Mutualistic Fungi
• Live in a mutualistic relationship with a plant or
alga
• The fungus receives energy from the plant, and
its mycelia increase water uptake and mineral
absorption for the plant.
Reproduction in Fungi
• Fungi are classified by their structures and
patterns of reproduction.
• Fungi can reproduce asexually and sexually.
• Asexual reproduction in fungi includes budding,
fragmentation, and spore reproduction.
• Sexual reproduction involves fungi producing
spores.
Reproduction in Fungi
Budding
• Reproduction method of unicellular fungi such as
yeast
• New cell develops while attached to the parent
cell
• The plasma membrane pinches off to partially
separate the new cell from the parent cell.
Reproduction in Fungi
Fragmentation
• Asexual reproduction that occurs when the
mycelium of a fungus is physically broken apart.
• If a fragment lands in a location with suitable
growing conditions, the hyphae will grow into a
new mycelia.
Reproduction in Fungi
Spore Production
• Most fungi are able to reproduce sexually and
asexually through spore production.
• A spore is a haploid reproductive cell
• Spores develop into a new haploid organism
• Haploid hyphae can fuse with other hyphae to
form diploid organisms.
Reproduction in Fungi
Spore Production
• Fruiting bodies of spore-forming fungi are called
sporophores.
• Sporophores are specific to the species of fungus
producing them.
• A sporangium is a sac or case in which spores
are produced.
Quiz
1. Which structure of fungi is different from plants?
A
composition of
cytoplasm
C
exoskeletons
B
composition of cell
walls
D
cellulose
CORRECT
Quiz
2. Which can be used for asexual and sexual
reproduction?
A
gametes
C
fragmentation
B
budding
D
spores
CORRECT
Quiz
3. Which does not describe a method by which fungi obtain
food?
A
parasitism
B
decomposition
C
photosynthesis CORRECT
D
mutualism
Quiz
4. What is the structure
shown?
A
mycelium
C
septate hyphae
CORRECT
B
spore
D
aseptate hyphae
Quiz
5. Which term describes the the portion of the
mushroom that is visible above the ground?
A
fruiting body
C
chitin
D
spores
CORRECT
B
septae