1. Fungi
Fungi are eukaryotic heterotrophs that have cell
walls.
The cell wall is made of chitin, a complex
carbohydrate found in the external skeleton of
insects.
Fungi unlike animals do not ingest their food. They
digest the food outside of their body then absorb it.
They absorb the nutrients from decaying organic
matter. Other fungi are parasites.
2. Structure and Function of Fungi
Except for Yeast, all fungi are multicellular.
Hyphae is a multicellular fungi composed of thin
filaments. Each hyphae is one cell thick.
Cross walls divide hyphae into cells that contain 1-2
nuclei. The cross walls have tiny openings through
which cytoplasm and nuclei can move. Other hyphae
lack cross walls and contain many nuclei.
3.
4. Structure and Function of Fungi
The bodies of multicellular fungi are composed of many
hyphae tangled together into a thick mass called
mycelium.
The mycelium is well suited to absorb food because it
permits a large surface area to come in contact with food
sources.
Fruiting body is the reproductive structure growing
from the mycelium in the soil beneath it. Clusters of
mushrooms are part of the same mycelium which means
they are part of the same organism
5. Structure and Function of Fungi
As time passes, the nutrients in the soil near the center
of the mycelium are depleted so the mushroom will only
sprout at the edges of the mycelium forming the “fairies
dancing in circles”.
6. Reproduction in Fungi
Most fungi reproduce asexually and sexually.
In asexual reproduction, the cells or hyphae breaks off
from the fungus and begin to grow on their own.
Some fungi produce spores which scatter and grow into
new organisms. Spore reproduce by mitosis. Sporangia
are structures which produce the spores. They are at the
tip of specialize hyphae called sporanophores.
8. Sexual Reproduction of Fungi
The sexual reproduction of fungi involves 2 different
mating types. Gametes of both mating types are about
the same size, they are not called female and male. The
mating types are (+) and (-).
When the hyphae of opposite type meet, they start
sexual reproduction by fusing by bringing (+) and (-)
nuclei together in the same cell. After a period of growth
and development the nuclei form a diploid zygote
nucleus and enters meiosis.
9. Structure and Function of Fungi
The spores are capable of growing by repeated rounds of
mitosis into a new organism.
10. How Fungi Spread
Many fungi produce dry almost weightless spores. These
spores scatter easily in the wind.
The spores will germinate if they land in a favorable
environment with the proper combination of
temperature, moisture, and food so that the spores can
grow. The probability that a spore will produce a
mature organism can be less than one in a billion.
11. How Fungi Spread
Other fungi are specialized to lure animals. Stinkhorns
smell like rotting meat which attracts flies. When the
fly lands on the stinkhorn the fly will ingest the sticky
smelly fluid on the surface of the fungus. The spore
containing fluid will pass unharmed out of the fly’s
digestive system, depositing spores over many
kilometers.
12. Classification of Fungi
Fungi is classified according to their structure and
method of reproduction.
Four Main Groups of Fungi
Common Mold - Zygomycota
Sac Fungi - Ascomycota
Club Fungi - Basidiomycota
Imperfect Fungi - Deuteromycota
13. Common Mold
The common mold grows on meat, cheese and bread.
They are in the phylum Zygomycota called zygomycetes.
Their life cycle includes zygospores.
Zygospore is a resting spore that contains zygotes which
formed during sexual phase of the mold life cycle.
14. Structure and Function of Bread Mold
Black bread mold Rhizopus stolonifer is dark and fuzzy.
2 different kinds of hyphae
1. Rhizoids is rootlike hyphae that penetrate the bread
surface. It anchors the fungus to the bread, release
digestive enzymes, and absorb digestive organic material.
2. Stolons is stemlike hyphae which run along the surface of
bread.
Sporangiophores has hyphae that push up into the air. The
sporangia form at its tips.
15. Life cycle of Molds
Sexual phase begins when hyphae from different mating
types fuse to produce gamete for structures called
gametangia.
Gametes of the opposite mating type form diploid (2N)
zygotes. The zygotes develop into thick walled
zygospores which may remain dormant for months.
When the conditions become favorable, the zygospore
will germinate then undergo meiosis. New haploid
spores are released. The signifigance of this sexual
process it the zygote formation is followed by meiosis.
16. Sac Fungi
Sac Fungi belongs to the phylum Ascomycota.
Ascomycetes is the name for the ascus, a reproductive
structure that contains spores.
Life Cycle of Sac Fungi includes asexual and sexual.
Asexual Reproduction – tiny spores called Conidia
formed at the tips of the specialized hyphae called
conidiophores. If the spores land in a suitable
environment it will grow into a haploid mycelium.
17. Sac Fungi
Sexual Reproduction occurs when the haploid hyphae of
2 different mating types grow close together. The
hyphae produce a fruiting body and sexual reproduction
continues.
Ascus forms with the fruiting body. Within the ascus,
the 2 nuclei of different mating type fuse together for a
diploid zygote. The zygote divides by meiosis producing
4 haploid cells. Meiosis is followed by a cycle of mitosis
then 8 cells are produced (Ascospores). Ascospores
germinate and grow into a haploid mycelium.
18. Yeast
Yeast is unicellular fungi. Yeast is classified as
ascomycetes because they form asci wit ascospores
during the sexual phase of their life cycle.
Budding is the process of asexual reproduction in yeast.
Ascospores become active in a moist environment.
Producing the byproducts of alcoholic fermentation
carbon dioxide and alcohol. The carbon dioxide makes
beverages bubble and bread rise.
19. Club Fungi
The phylum for Club Fungi is Basidiomycota name from a
specialize reproductive structure that resembles a club.
Basidium is a spore bearing structure. Basidia if found on the
gills that grow on the underside of a mushroom caps.
Life Cycle of the Club Fungi
Basidiospores germinate to produce a haploid primary
mycelium which begins to grow. A secondary mycelium is
produced. Spores producing fruiting bodies push above the
ground. Fruiting bodies are mushrooms. Each mushroom
begins as a mass of growing hyphae that forms a button or
thick bulge at the soil’s surface.
20. Club Fungi
Fruiting bodies expand with astonishing speed
producing fully developed mushrooms overnight. The
remarkable growth is caused by cell enlargement, not
cell division. The cells of the hyphae enlarge by rapidly
taking in water.
Each gill is lined with basidia.
21. Imperfect Fungi
The imperfect fungi belongs to the phylum
Deuteromycota. This fungi is not place in other phyla
because researchers have never been able to observe a
sexual phase in the life cycle.
Imperfect fungi is closely resembles ascomycetes. The
most known genera of this group is Penicillium. It grows
on fruit and is the source of antibiotic penicillin.
Penicillin evolved from an ascomycota that lost the
sexual phase of its life cycle.
