4. The Mycota (fungi)

Question 1

What are the impacts of fungi on humans and plants?

Answer 1

• sources of food or used for food fermentation
• sources of pharmaceuticals
• sources of enzymes
• plant and animal diseases
• symbiotic relationships with plants

Question 2

Describe fungal structure

Answer 2

• grow as filaments or as yeast
• vegetative (feeding) structure is a mycelium
• cell walls feature chitin microfibrils embedded in a matrix of polysaccharides, protein & lipids

Question 3

What are mycelium

Answer 3

Mycelium is a network of hyphae: monofilaments (cytoplasm in a tube) with large surface area/volume ratio

Question 4

What are septa?

Answer 4

• Hyphae are divided by cross walls called septa

* septa are incomplete and allow cytoplasmic continuity

Question 5

Define anastomose

Answer 5

• Fusion between branches of the same or different hyphae

* hyphae can fuse - anastomose

Question 6

What are heterokaryons?

Answer 6

• cells with multiple nuclei that are genetically different

Question 7

Fungal hyphae structure

Answer 7

• hyphae are divided by septa
• septa are incomplete - allow cytoplasmic continuity
• capable of indefinite growth

Question 8

Describe fungal reproduction

Answer 8

Reproduce by
• produce hyphae
• by budding/fission (yeasts)
• through formation of sexual and/or asexual spores

• Dikaryons are formed by plasmogamy of compatible mating types

Question 9

Plasmogamy

Answer 9

• stage in the sexual reproduction of fungi in which the cytoplasm of two parent cells (usually from the mycelia) fuses together without the fusion of nuclei
• brings two haploid nuclei close together in the same cell

Question 10

karyogamy

Answer 10

Fusion of 2 nuclei

Question 11

chromosome number in cells after fungal reproduction

Answer 11

• meiosis follows after karyogamy & zygote(2n) formation

* nuclei in vegetative hyphae are haploid (n)

Question 12

Are fungi autotrophs or heterotrophs?

Answer 12

heterotrophs

Question 13

How do fungi spread?

Answer 13

Spore formation allows fungi to spread in nature

Question 14

Nutrition of fungi

Answer 14

• secrete enzymes and digest food externally - food absorbers
• reserves stored as glycogen, fats and oils

Question 15

Saprophytic fungi

Answer 15

• decompose cellulose & lignin
• wood rot fungi
• major recycler

Question 16

Saprophytic fungi environmental tolerance

Answer 16

• means they grow almost everywhere other organisms are found

Question 17

What is lignin

Answer 17

• type of material found in woody plants

* lend rigidity and important in formation of cell walls in plants and wood

Question 18

Parasitic fungi

Answer 18

• specialised structures & nutrition
• rusts, blights, wilts and rots plants
• mycoses and allergies
• predators - nematode trapping fungi

Question 19

What is a nematode?

Answer 19

Worm of the large phylum nematoda - roundworm or threadworm

Question 20

What are beneficial associations of fungi?

Answer 20

• Mycorrhizae (fungi + plant roots)
• endophytes (above ground plants)
• lichens (fungi and algae)
• with invertebrates: leaf cutting ants, termites and their fungus ‘gardens’

Question 21

Mode of action of mycorrhizae

Answer 21

• fungus grows between and eve into plant root cells

* fungi extract sugars and fats from the plant in exchange for mineral nutrients and water it extracts from the soil

Question 22

Why are fungi efficient soil nutrient extractors?

Answer 22

large surface area to volume ratio

Question 23

What are the benefits of mycorrhizae?

Answer 23

• 95% of plants rely on mycorrhizal associations

* allows plants to grow in more nutrient poor

Question 24

What is mycorrhizae?

Answer 24

• fungal association with plants - symbiotic relationship

* intimate associations between fungus and root cells allows nutrient exchange

Question 25

Describe fungal evolution

Answer 25

* evolved from a Protist similar to extant choanoflagellates * one line led to sponges and animals * other to chytrids and other fungi

Question 26

Why did the dikaryon life stage develop?

Answer 26

Developed in fungal evolution in place of diploid 2n stage

Question 27

what did Ascomycota and Basidiomycots evolve from?

Answer 27

From shared ancestor Dikarya

Question 28

Chytrids

Answer 28

* aquatic or soil borne * motile zoospores - the only fungi with flagella * limited coenocytic mycelium - no regular septa * parasites, saprophytes and mutualists

Question 29

Saprophytes

Answer 29

A plant, fungus, or microorganism that lives on dead or decaying organic matter.

Question 30

define coenocytic

Answer 30

An organism made up of a multinucleate, continuous mass of protoplasm enclosed by one cell wall, as in some algae and fungi.

Question 31

What is mycelium

Answer 31

the vegetative part of a fungus, consisting of a network of fine white filaments (hyphae)

Question 32

Zygomycetes

Answer 32

* hyphae are coenocytic * fruit moulds, insect pathogens * uncommon human pathogens

Question 33

What are the sexual and asexual spores of zygomycetes called?

Answer 33

* sexual: zygospores | * asexual: sporangiospores

Question 34

Ascomycetes

Answer 34

* yeast, truffles, moulds * hyphae have regular septa * dikaryon limited to reproductive tissues

Question 35

Describe the reproduction of ascomycetes

Answer 35

* dikaryon limited to reproductive tissue * meiosis follows zygote formation within the ascus, forming ascospores * asci may be surrounded by a fruiting body * asexual (mitotic) spores are conidia

Question 36

Basidiomycota

Answer 36

* mushrooms, toadstools, rusts, puffballs * vegetative hyphae are septate * basidia may be born on a basidiocarp *  asexual conidia uncommon *  some yeast forms

Question 37

What is a conidia?

Answer 37

A spore produced asexually by various fungi at the tip of a specialized hypha.

Question 38

What is the MAT locus and its function?

Answer 38

*  a mating type locus found in all fungi to control their ability to undergo sexual reproduction * small part of one chromosomes rather than an entire chromosome

Question 39

Why did fungi lose its flagella during evolution?

Answer 39

As an adaption to dry tolerance