1. Chapter 18
Fungus

2. 18.1 Fungi are adapted for nutrition by absorption
hyphae: tiny threads of cytoplasm surrounded by a plasma membrane and covered by a cell wall
Cell walls made of chitin
Strong , flexible polysaccharide
Cross-walls: divide the long filaments into many cells
Exchange cytoplasm, organelles and distribute nutrients

3. Mycelium mycelium(mycelia): interwoven mat of hyphae Feeding structure
Maximizes surface area within food
Km of hyphae each day
In Oregon, mycelium is 5.5 km across, 9 km2 of forest, 2400 years old

4. Nutrition
absorptive nutrition: method by which the fungus absorbs small organic molecules from its surroundings
Digests food outside mycelium by secreting enzymes
Enzymes break down molecules so they can be absorbed
Food sources
Fallen logs, dead animals, waste
Parasitic fungi: absorb nutrients from living hosts

5. Reproduction spores: haploid single cells with thick cell walls
Spread by wind and can withstand unfavorable conditions
Most are asexual
Sexual reproduction: haploid hyphae from different mycelia fuse together and combine genetic info
Can produce trillions of spores
Puffballs
Found 200 km above the surface

6. 18.2 Kingdom Fungi consists of diverse forms

7. Zygote Fungi Mostly terrestrial and live in soil or decaying material
Rhizopus stolonifer
Food available= asexual reprod.
Sporangia: spore-forming structures at tips of hyphae
Food depleted= sexual
Two mycelia fuse
zygosporangium: reproductive structure

8. Sac Fungi Marine, freshwater, and terrestrial
Single-celled or large morels
Ascus (sac) contains spores
Similar reproduction to zygote fungus

9. Club Fungi Agaricus bisporus Most common
Important decomposers of wood and plant material
Some are parasites
Usually sexual
Spores drop from “gills” underneath
Can grow within hours

10. Club Fungi Reproduction

11. Yeast Single-celled fungi Inhabit liquid or moist habitats
Plant sap and animal tissues
Reproduce asexually
Cell division or pinching of “buds”
Some sexually
Form ascus or basidium; classified as sac or club
Imperfect fungi: no known sexual stage of reproduction
Used for fermentation or raise dough

12. Mold Any fungus that grows very rapidly on a surface Most asexual
Some imperfect
Sexual stages place some in zygote, sac, or club
Rhizopus - zygote
Penicillium - sac

13. Mmmmm…. cheesy

14. 18.3 Fungi have a major impact on other life.
Symbiotic fungi
Close relationship between two different species that benefits at least one of them
Mutualistic: both benefit

15. Lichen lichen: mutualistic pairing of a fungus and an alga
Photosynthetic algae feed the fungus
Fungal mycelium provides a good habitat
Usually a sac fungus and either green algae or cyanobacteria
More than 25,000 “species” of lichen

16. Benefits of lichen symbiosis
Environments where neither could live on its own
Pioneer organisms
Tundra
Do not tolerate air pollution; death of lichen = poor air quality

17. Mycorrhizae
Symbiotic relationship between fungal hyphae and plant roots
Fungus provides
more water and nutrients, plant provides sugar
Mushrooms
around trees

18. Disease-causing fungi
30% of fungi are parasitic
Dutch Elm disease
Eliminated most elm trees in N Amer
50 species parasitic in humans and other animals
Yeast infections
Ringworm
Athlete’s Foot

19. Commercial Uses Truffles Cheese Yeast for baking and brewing
Fungi “ripen” them
Yeast for baking and brewing
Antibiotics

20. Chemical Cycling Decompose matter Circulate carbon and nitrogen
Some can decompose clothing, boots, glue, and plastic