Transcript The Fungi
Kingdom Fungi-Introduction
This is a very diverse
group of organisms that
includes yeasts, molds,
rusts, and smuts.
Fungi lack chlorophyll
and do not carry on
photosynthesis.
Most are saprobes,
although some are
parasitic.
Kingdom Fungi-Intro.continued
Saprobes (shown
here), release digestive
enzymes that break
down food.
Nutrients are then
absorbed into the
fungal cells.
Parasitic fungi obtain
their nutrients directly
from their hosts.
General Fungi Characteristics
Consist of threadlike
filaments called
hyphae.
Hyphae grow in a
tangled mass to form
the mycelium.
The hyphae are made
up of cells containing
the cytoplasm.
General Characteristics
continued
Fungal cells may or may not
have cross walls (partitions).
Cells with cross walls are called
septate.
Fungal cells may be
multinucleate.
Cell walls are made up of chitin
(a polysaccharide)
Reproduction is both asexual
and sexual by means of spores.
80 000 species exist.
The Five Groups of Fungi
The fungi are divided into 5
groups based on their mode of
reproduction:
Group 1: Phylum Zygomycota.
Known as the zygomycetes.
Both sexual and asexual
reproduction exist.
Hyphae lack crosswalls. But
crosswalls do form during
gamete production.
Most are saprobes and some are
parasitic.
Bread Mold - Rhizopus sp.
Bread Mold Gone Bad !
Phylum Zygomycota
Sexual Reproduction in Rhizopus
Group 2 Phylum Oomycota
Phylum Oomycota
The Water molds
Most are saprobes and some are parasites on
fish.
Some are plant parasites such as the late blight
fungus that caused the Irish Potato Famine
(1845-1847).
Only group with motile flagellated spores.
Only group with structurally different male and
female gametes (sperm and eggs).
Phylum Oomycota continued
Cell walls made of cellulose and not chitin.
Hyphae have no cross walls.
Diploid stage is dominant in their life cycle.
Group 3 Phylum Ascomycota
Largest known group.
Multicellular
Hyphae have cross walls.
Sac fungi form two types of spores:
Sexual Spore-produces in a sac-like structure
called the ascus. 8 ascospores per ascus.
Asexual Spore-Produced at the tip of specialized
hyphae called conidiophores. The spores are
called conidia.
Ergotism-An Ascomycete
Disease.
Disease caused by the
plant parasite,
Claviceps purpurea.
Grows on rye.
Bread made with
contaminated rye,
causes severe illness in
humans.
Ergotism continued
Symptoms include
gangrene, nervous
spasms and convulsions.
Ergot is used in medicine
to cause blood vessels to
constrict.
It is the initial source of
the psychedelic drug
LSD.
Group 4 Phylum-Basidiomycota
Phylum Basidiomycota
The club fungi.
Spores form in a club-shaped structure
called the basidium.
The spores are called basidiospores.
Hyphae are divided by incomplete
crosswalls.
Cells have two nuclei.
Group 5 Imperfect Fungi
These molds do not fit into the other groups
of fungi, as they lack sexual stages in their
life cycles and hence are said to be
imperfect.
Reproduction is asexual by way of spores.
Some are predatory and trap protists and
small round worms.
Predatory Fungus
A Captured Nematode
Mycorrhizae
Many fungi form symbiotic
associations with the roots of
green plants, by way of
mycorrhizae (“fungusroots”).
Some of these fungi form
distinct layers on the outside
of roots (ecto-mycorrhizae),
while others are deep in the
roots.
Mycorrhizae
The fungi get sugars from the
plant host.
The plant itself gets nutrients
from the fungi, including
nitrogen and phosphorous.
The mycorrhizae also protect
plants from heavy metals by
acting as filters.
The Lichens
Lichens are formed
when certain algae
join with certain
fungi.
Mr. Fungus
Mr. Algae
Lichens-A Symbiotic
Relationship
Together, the algae and the fungus form a
living unit.
What we have here is a symbiosis.
The algae through photosynthesis produce
sugar as a food source,
and the fungus provides support and
protection from drying.
General Structure of a Lichen
Foliose lichen – resembles lettuce.
Crustose Lichen – Fairy barf
Fruticose lichen-Old Man’s Beard
Microscopic View of a Lichen