How do Fungi acquire nutients?
They are Heterotrophs that get nutrition from absorption
-- secretes hydrolytic enzymes into food then absorbs
-- therefore they are decomposers, parasites, or mutualistic
symbionts (Lichens – fungi and algae living together)
Because of this mode of nutrition, fungi have evolved what structure
to provide for both extensive surface area and rapid growth?
Mycelium – interwoven mats made of hyphae
Hyphae – small threads made of tubular
cell walls (made of chitin)surround the
plasma membrane. They are divided into
cells by cross walls called septa.
Images from
your book.
Figures 31.2
and 31.3
How do cell walls of fungi differ from the cell walls of plants?
Plants cell walls are made of cellulose
Fungi cell walls are made of chitin
What are the septa comparable to in plant cells (even though septa
are bigger)?
Plasmodesmata
Define these terms:
Mycelium – Densely branched network of hyphae in a fungus
Septa – A cross wall that divides a fungal hypha into cells. Pores are large
enough to allow ribosomes, mitochondria, and nuclei to flow from cell
to cell.
Coenocytic fungi – a fungus that lacks septa. It’s body is made up of a
conitnuous cytoplasmic mass that may contain hundreds or thousands
of nuclei.
Haustoria – modified hyphae on parasitic fungi enabling it to penetrate
the cell walls of plants (however, it remains enclosed in the plasma
membrane of the plant).
Mycorrhizae – mutualistic relationship between plant roots and fungi
-- Plant provides fungus with a steady supply of sugar
-- Fungus increases the suface area for water uptake and also
supplies plant with phosphate and other minerals absrobed from
the soil. Fungus also secretes growth factors that stimulate roots
to grow and branch and antibiotics that help protect the plant
from disease.
Ectomycorrhizal Fungi – Forms a dense sheath over the surface of the
root
Arbuscular mycorrhizal fungi – (aka Endomycorrhizae) – microscopic
fungal hyphae extend into the root. Makes extensive contact with the
plant through brancing of hyphae that forms arbuscules.
Reproduction
Fungal spores
a. reproduced sexually or asexually (Sexual reproduction only
occurs when there has been some change in environment)
b. unicellular or multicellular
c. produced in specialized hyphal structures
d. carried by wind or water
a. contributes to adaptation in changing environment
Plasmogamy
Union of 2 parent
mycelia
Heterokaryotic
Stage “different nuclei”
Dikaryon (n+n)
Karyogamy
Haploid nuclei fuse
producing a diploid
cell
“two nuclei”, one cell
Mycelium (n)
Diploid Stage (2n)
Germination
Spores
(n)
Spore
producing
structures (n)
Meiosis
immediately
Spore Producing
Structures (n)
Mycelium (n)
Spores (n)
Germination
How do fungi contribute to an ecosystem?
Decomposers
Some produce antibiotics
Food
Yeast (alcohol, bread)
Cholesterol lowering drugs
High blood pressure medicine
Molecular genetics research (easy to culture and manipulate)
What are some examples of how fungi are important to humans?
Diversity of Fungi (4 divisions)
1. Chytridiomycota
a. may be link between fungi and other Eukaryotics
b. mainly aquatic
c. decomposers or parasitic
d. make uniflagellated spores called zoospores
e. coenocytic hyphae
f. most primitive
2. Zygomycota – “zygote fungi”
a. mostly terrestrial
b. live in soil or on dead plants and animals
c. major group forms mycorrhizae
d. coenocytic – septa only found where reproductive cells are
formed.
e. common one is black bread mold
3. Glomeromycetes (formerly thought to
be Zygomycetes)
a. Many plants form mycorrhizal
associations with this fungi
4. Ascomycota – “sac fungi”
a. all habitats
b. lichens, mycorrhizae, live on leaves and release toxins to
protect plant from insects
c. defining feature – production of sexual spores in saclike asci
This is the sexual stage – dikaryon – seen in macroscopic
fruiting bodies called ascocarps
Dikaryon hypae give rise to asci
Karyogamy takes place withing asci
Meiosis produces ascospores (8 in a row)
****Think meiosis lab!!!!!!
5. Basidiomycota – “Club Fungi”
a. mushrooms, puff balls
b. decomposers, mycorrhizae, parasites
c. long lived dikaryotic mycelium
d. reproduces sexually
6. Lichens
a. Symbiotic association of millions of photosynthetic
microorganisms held in a mesh of fungal hyphae.
Algae provides fungus with food
Fungus gives algae a suitable environment for
growth