Download 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