Lecture 5 - Fungi Flashcards
1
Q
What are characteristics of fungi
A
- Essential decomposers
- Found everywhere and affect ecosystems by feeding on living and dead organic material
- Heterotrophs that digest food externally.
- Eukaryotic organisms
- Non-vascular, with no roots, stems or leaves
- Possess chitin in the cell wall. ( The same material arthropods possess in their exoskeleton
- They do not photosynthesise, no chloroplast
2
Q
Explain fungi being heterotrophic
A
- Saprotrophs - decomposers
- Parasitic – attack living tissue
3
Q
Explain the relationship of fungi and cynobacteria or algae
A
- Forms symbiotic relationships
- Forms lichens
4
Q
Explain the structure of fungi
A
- Thallus (body) of fungi is multicellular, called mycelium
- Mycelium consist of threads called hyphae
The hyphae of fungi are septate and non-septate - Non septate hyphae : many nuclei in cytoplasm, No seta or cross walls
- Septate- hyphae is divided into cells- pores in the cross walls
- Cell walls of fungi consist of chitin (also in exoskeleton of arthropods)
- Septa that separate reproductive cells are complete
- Fungi store energy as glycogen-same as in animals
- Terrestrial fungi has no flagellated cells
- Growing hyphae can cover a km in a day
5
Q
Explain the reproduction of fungi
A
- During sexual reproduction haploid hyphae from two different mating types fuse
- If nuclei do not fuse immediately the resulting hypha is dikaryotic (n+n)
- Fungal spores germinate into haploid hyphae
- Spores are an adaptation to life on earth- ensures that species will disperse to new locations
- Spores are produced sexually as well as asexually
- Spores are dispersed by the wind
- Asexual reproduction by three mechanisms:
1. Production of spores by a single mycelium
2. Fragmentation of a mycelium
3. Budding as in yeasts
6
Q
Explain Phylum: Chytridiomycota/ Chytridiomycetes
A
- Most primitive group of fungi.
- 790 spp. – They possess a simple structure and possibly resemble ancestral fungi.
- Live in aquatic or damp habitats
- Possess flagellated cells.
- Gametes and spores (zoospores), are flagellated. They are the only group of fungi with flagellated cells.
- The presence of zoospores place fungi in Supergroup Opisthokonts
- They are either saprotrophs or parasites.
- They decompose cellulose, keratin and chitin
Example: Batrachochytrium dendrobatidis
7
Q
Explain Phylum Zygomycota/ Zygomycetes
A
- They are saprotrophic; live on plant and animal remains in soil; some are parasites
- Example is Rhizopus stolonifera (bread mold)
- They have different types of hyphae
1. Stolons: horizontal hyphae on surface of bread
2. Rhizoids hyphae that grow into bread
3. Sporangiophores: Aerial hyphae that bear sporangia. The sporangium produces spores’ - The zygospore is seen during sexual reproduction. Sexual reproduction takes place in unfavorable conditions.
8
Q
Explain Phylum: Glomeromycota/ Glomeromycetes
A
- Also known as AM Fungi = arbuscular mycorrhizal fungi (160 spp).
- An arbuscular mycorrhiza is a type of mycorrhiza in which the fungus penetrates the cortical cells of the roots of a vascular plant.
- They are responsible for forming mutualistic associations calledendomycorrhizaewith the roots of about 70% of the world’s plants.
- Ectomycorrhiza forms a mantle exterior to the root
- AM fungi make branching incisions in root of plants (arbuscule); only through cell walls. Provide roots with extra surface area for absorbing nutrients- plant provides the fungus with carbohydrates
- Mycorrhizae is a mutualistic association which benefits both the plant and the fungus.
9
Q
Explain Phylum: Ascomycota/Ascomycetes
A
- They are also called sac fungi
Two major forms: sexual and asexual sac fungi - Yeasts (Saccharomyces) reproduce asexually through budding (brewer’s yeast) or sexually to form ascospores (n) in asci
- Yeasts are used for fermentation, produces ethanol and CO2, it is used in the baking and brewing industry, as well as in genetic engineering
Candida albicans:
vaginal infections,
oral thrush
Red bread moulds,
truffels and
morels are all sexual sac fungi
10
Q
Explain Phylum: Ascomycota
A
- Asexual sac fungi previously placed in Phylum: Deuteromycota – imperfect fungi
- Either highly beneficial or (extremely) detrimental to human health
- Penicillium sp.was renamed Talaromyces sp.- Penicillin antibiotic is derived from this
- Aspergillus sp.- used for soy sauce production;
- A. flavus secretes aflotoxin on moist seeds– most potent natural carcinogen
- Black mould – Stachybotrys chartarum causes sick-building syndrome
- Diseases – ergotism (poisoning caused by eating food infected by ergot fungi, resulting in headache, vomiting, diarrhoea, and gangrene of the fingers and toes).,
- Ringworm, athlete’s foot, thrush are all diseases caused by molds or sac fungi.
11
Q
Explain Phylum Basidiomycota/Basidiomyetes
A
- Basidiomycota Includes mushrooms, bracket fungi, puffballs.
- Some are edible and others are deadly poisonous. Some are hallucinogenic
- They are also called club fungi
- Smuts and rusts are club fungi, that don’t form a basidiocarp
- Smuts and rust parasitize corn, wheat etc.
- It cause crop losses
- They have Septate hyphae
12
Q
Explain fungi and alien control
A
- Uromycladium tepperianum – is a rust fungus that causes acacia gall.
- The rust produces chemicals that cause trees to produce large conspicuous galls
- The galls are formed on the “leaves”, and the seedpods.
- It is used in the control of the alien tree, Acacia saligna (Port Jackson )
- Introduced to S.A. in 1987
13
Q
Explain lichens
A
- Symbiotic relation between fungus and alga or cyanobacterium
- The association is considered mutualistic but experimentation suggests a controlled parasitism by the fungus of alga
- Three forms of lichens :
1. Crustose often seen on rocks and tree bark
2. foliose- appear leaflike
3. fruticose-appear shrublike - Good indicator of air quality. More lichen growth in areas with low air pollution.
- Lichens take up polutants
- Lichens secrete acids that break down rock. This contributes to the soil-building process.
