3/22/2011
Review
Review
Mitosis: division of cells that results
in two identical daughter cells with
same genetic information as the first
cell
Meiosis: division of cells that results
in daughter cells with one-half of
the genetic information that the
original cell had.
8
4
4
8
8
4
8
Diploid
• Meiosis is required for sexual reproduction
- otherwise chromosome no. would double
in offspring
4
Haploid
How do mitosis and meiosis fit into the
life cycles of sexually reproducing
organisms?
• Gametes and some spores are the result
of meiosis
- some spores arise from mitosis
• two gametes fuse (syngamy) = zygote
Simple organisms
• How do mitosis and meiosis fit into the life
cycles of sexually reproducing
organisms?
Gametes
Zygote (2n)
Mitosis
Meiosis
n
1
3/22/2011
Alternation of generations (plants)
Animals
Sporophyte (2n)
Mitosis
Meiosis
Zygote
Meiosis
Mitosis
Gametes
Gametes (n)
Spore (n)
Zygote (2n)
Zygote
Mitosis
Gametophyte (n)
Kingdom: Fungi - Chapter 26
Kingdom: Fungi
• ~ 100,000 named species
1. Eukaryotic cells
2. Most have cell walls with chitin (a
polymer – subunits of nitrogen containing
sugar - cell walls do not have cellulose
3. Heterotrophs (most Saprotrophs) orgs.
That obtain energy from dead organic
material by absorbing it!
4. Secrete digestive enzymes
Ecologically important:
• Decomposers (breakdown organic
molecules) and nutrient release
Health issues:
• food, our bodies, allergies, crops
Beneficial:
• Foods - drugs
Two main types:
1) Yeasts (unicellular)
2) Molds
Filamentous growth form: Hyphae - slender
filaments bundled together to form
the fungus
Hyphae: Filaments - Vegetative part of
fungus – nonreproductive part - chitin
reinforced walls
Tangled mass of hyphae = Mycelium
What we see is aerial Mycelium
= Fruiting body
2
3/22/2011
Fungi reproduce sexually and asexually
Hypha filament
• Most by means of microscopic spores
• Most have Septa = walls dividing
cells
• Rarely form a complete barrier
• >1 nuclei per cell
- spores may be haploid or diploid
(in plants always n)
- can germinate without fertilization
- always nonmotile
- Sporangia: Structures where spores are made
Asexual reproduction
• Spores Produced by mitosis (Conidia)
• Conidiophores: special hypha
produce Conidia (asexual spores)
Spore germination
Unlike most plant and animal cells most
fungal cells are not dipoid
• 2 types of sexual reproduction occurs
In sexual reproduction two hyphae of
different strains come together,
their nuclei fuse = form a diploid
zygote.
Plasmogamy – cytoplasm fuses
3
3/22/2011
Sexual reproduction takes place when
2 nuclei fuse within a dikaryotic cell
(Karyogamy)
N+N
Hypha
Nucleus
2n
Monokaryotic = 1 nucleus per cell (n)
Nucleus zygote (2n)
Hypha
Hyphae
Coenocytic = no septa, numerous nuclei
Dikaryotic = 2 nuclei per cell (n + n)
95%
Basic sequence for most fungi
1. Fossil evidence not great
2. 225 mya spores
3. 550 mya algae hyphae
Fig. 26-4, p. 559
Fig. 26-5, p. 560
4
Basidiomycetes
Ascomycetes
• Based on sexual spores and fruiting
bodies – AND DNA
• Phylum Chytridiomycetes (Chytrids)
- Flagellated cells
- Alternation of generations
- Ancestor to other fungi??
Glomeromycetes
Chytrids
Five phyla
Zygomycetes
3/22/2011
basidospores
Evolution of
Dikaryotic stage
Common
flagellate
ancestor
Loss of
Flagellum
Fig. 26-9a, p. 564
Fig. 26-6, p. 561
Morel
Fig. 26-8, p. 563
Fig. 26-21a, p. 575
5
3/22/2011
Fig.26.13
Basidiomycota
30,000 spp.
Basidia
Basidiomycetes
Ascomycetes
Glomeromycetes
Zygomycetes
Chytrids
Fig. 26-14a, p. 568
Common
flagellate
ancestor
Fig. 26-17a, p. 571
n
n
meiosis
2n
N+N
Fig. 26-16, p. 570
6
3/22/2011
Fig. 26-15a, p. 569
Fig. 26-15b, p. 569
Fig. 26-15c, p. 569
Fruticose liche (Ramalina)
Lichen: symbiotic relationship between
fungus and algae
• Fungus get nutrients from algae
• Algae gets Protection from sun?
• Protection from elements
Crustose lichens
(Bacidia, Lecanora)
Ecologiclly important: break down of
rocks - - air quality
Foliose lichen
(Parmelia)
Fig. 26-20b, p. 573
7
3/22/2011
Mycorrhizae: symbiotic relationship
between plants and fungi
• grows on roots of plants
• enhances uptake of water and nutrients
No mycorrhizae
with Mycorrhizae
Fig. 26-24a, p. 577
Fig. 26-24b, p. 577
8