Chapter 31 - Fungi
IV. Kingdom Fungus
A. Estimated 1.5 million species
B. Greek, mycos, fungi (mycelium, mycorrhizae, etc…)
C. Some are single-celled (in general known as yeast), while
most are complex multicellular
D. Fungi are heterotrophs that absorb food after digesting with
enzymes they secrete outside their body called exoenzymes
hyphae
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 1. Saprophytes (saprobes, decomposers)
- Break down and absorb nutrients from non-living organic material like
a fallen log, dead animals and organismal waste (feces, etc…)
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 2. Parasitic / Pathogens
- Take nutrients from living cells, some pathogenic – 80% of plant
diseases caused by fungus.
“Athletes Foot”
Blithe
Only 50 out of the known 100,000 fungal species are parasites of animals and these do relatively little damage.
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 3. Mutualistic symbionts
- mycorrhizae
mycorrhizael
hyphae
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
F. Body Structure
1. Multicellular fungus
- Hyphae - Network of tiny filaments making up body of fungus
- Cell walls are made of… Chitin = polysaccharide of
modified glucose also
found in exoskeletons of
insects and crustaceans
(arthropods)
- Mycelium (plural, mycelia) – entire interwoven mass of hyphae
- High surface area to volume ratio, efficient feeding
- 1ml of soil may contain 1km of hyphae
- Like plants, hyphae need to GROW through environment
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
F. Body Structure
1. Multicellular fungus
- Structure of Hyphae
a. Septate hyphae - Most fungi have
hyphae divided into cells by septa
(crosswalls) with large pores for sharing
material
b. Coencytic hyphae – continuous
cytoplasm with many, many nuclei due to
repeated mitosis without cytokinesis similar
to slime molds.
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
1. Produce spores either
sexually or asexually
- Carried by wind or water
- We see this when we leave food
out or in fridge too long…spores
are everywhere in the air….
Puffball mushroon exploding releasing trillions of spores
Chapter 31 - Fungi
Spores vs Gametes
Spore
Cell or cell-like structure involved in asexual reproduction
May be adapted for dispersal and/or survival in unfavorable conditions
Part of life cycle of many
- plants
- fungi
- algae/protozoan (protists)
Gametes
Cells of sexual reproduction
Alternation of Generation in Plants
Chapter 31 - Fungi
Questions
1. The “root-like” structure of a multicellular fungal organism.
2. Mycellium – define.
3. Spore vs. Zygote – similarities and differences
4. Kingdoms of life that have evolved to utilize spores to reproduce.
5. Ploidy of mycellium.
6. Any single-celled fungus.
7. When a single cell fungus reproduces by mitotic cell division, but new
cell pinches off the parent cell and is smaller to begin with.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
- Many, but not all reproduce both
sexually and asexually. Some do one
or the other.
Start here
Nuclei of hyphae
(mycellium) and spores
are haploid!!
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
General life cycle of fungus
- Many, but not all reproduce both
sexually and asexually. Some do one
or the other.
- nuclei of hyphae and spores are
haploid.
Specific Example you need to know
from the Ascomycota phylum
- The five major fungi phyla – I would
not memorize these…
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
Fusion of two cells, a plus (+) and a
minus (-), resulting in the combining of
the cytoplam (hence plasmogamy).
The nuclei do not fuse yet and
therefore the cell is dikaryotic (two
nuclei).
Very much like
Fertilization of
gametes
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
- Begins when two distinct mycelia of
different mating types (+ and -) secrete
pheromones that bind to receptors on
each others surfaces.
- Hyphae then grow toward each other
using mitotic cell division (they follow
the pheromone) and fuse those cells
that meet from the + and – will fuse =
plasmogamy.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
In the case of ascomycetes, the minus
(-) cells move toward the plus (+) cell
hyphae, bind, and then fuse
(plasmogamy) forming a dikaryotic
cell known as an ascus.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
B. Karyogamy
Fusion of the two nuclei of the
dikaryotic cell forming a diploid
cell…the ZYGOTE (could occur hours,
days or years later).
This is similar to a sperm fusing with
an ovum. Both haploid followed by
plasmogamy, then karyogamy to form
the zygote!!
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
B. Karyogamy
C. Meiosis
- Meiosis follows karygomy restoring
haploid mycelium that will produce
spores.
Specifically in the ascomycotes,
meiosis occurs, but not cytoplasmic
division resulting in a four haploid
nucleus cell.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
B. Karyogamy
C. Meiosis
D. Mitosis
- Mitosis of the haploid cells will
produce spores of the (+) and (-) types.
In the ascus, mitosis occurs resulting in
an eight haploid nucleus cell (ascus).
Cell walls form around the nuclei
turning them into spores (ascospores)
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
A. Plasmogamy.
B. Karyogamy
C. Meiosis
D. Mitosis
E. Germination
- The (+) and (-) spores grow by mitotic
cell division to form new mycelia
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
ASexual reproduction
- Minus (-) Mycelia (haploid) will use
mitotic cell division to make spores and
these spores will become new mycelia.
Conidia = Asexual spores of ascomycetes
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Molds
- Any multicellular fungus that can
reproduce rapidly and asexually. It is
a general term. Many of these fungi
can reproduce sexually, but mold refers
only to the asexual stage.
Yeast
- Reproduce predominantly asexually
not by using spores, but by budding, a
type of simple form of cell division.
Sometimes they reproduce sexually.
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
The five major phyla of fungi:
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
4. Ascomycetes
- 32,000 species
- Production of sexual spores in saclike asci
- Therefore commonly called sac fungi
- Vary from unicellular yeast including bread/beer/wine making
yeast (Saccharomycetes cerevisiae) to cup fungi and morels
- Consist of some of most deadliest plant pathogens
making them relevant to agriculture
- More than 40% are lichens – mutualistic relationship
between fungi and unicellular chlorophytes (green algae)
or with cyanobacteria.
- Others form mycohorrhizae
Lichen growing on a tree:
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
4. Ascomycetes
Lichen:
A mutualistic relationship between:
1. ascomycete fungus and
green algae
or
2. Ascomycete fungus and
cyanobacteria.
- Algae/cyanobacteria do photosyn and
produce organic compounds for fungus,
while fungus provides place to live as
well as water and minerals obtained
mostly from airborne dust or rain – why
they can grow on rock ( hence pioneer
species in primary succession).
The algae will reproduce asexually.