Fungi - Chp 21 just practical nf

Mycology

the study of fungi

What are the characteristics of fungi?

• eukaryotic/have membrane bound organelles

• reproduces asexually + sexually

• heterotrophic

• have cell walls made from chitin

• made up of many tubes called hyphae which form a visible mycellium

• multinucleate

Hypha

tube or filament in a fungus

Mycelium

visible mass of hypha

Parasitic Fungus + Example

• live in or on another living orgnanism causing harm

• athlete’s foot

What is an obligate parasite?

lives on a host and does not cause it harm or kill eg mildew

What is a facultative parasite?

kills the host and feeds on the dead remains eg soft rots in fruit

Saprophytic Fungus + Example

live on dead organisms: decomposers eg mould

Examples of edible fungi

standard fiel mushroom - above ground

truffle - below ground

Examples of poisonous fungi

death cap + destroying angel

How is food digested by fungus?

• digested extracellularly

• enzymes are secreted onto the food

• nutrients are absorbed into the hyphae

What is a method of identification of fungi

spore prints

What does Aseptate mean?

nuclei in the fungus are not separate by walls and can move freely in the hyphae

What is the name of common bread mould?

Rhizopus

What type of fungus is rhizopus?

saprophytic

Rhizopus diagram

Hyphae - function

secrete digestive enzymes + absorb the digested food

Stolon - structure

aerial hyphae growing horizontally that spread over the surface + turn downward to create rhizoids

Rhizoids - function + structure

branched hyphae that penetrate the food source + anchor the fungus

releases digestive enzymes + absorbs the digested food

Sporangiophore - structure

hyphae that grow up from the surface of the substrate vertically

Sporangium - structure

swelling at the ip of a sporangiophore containing spores which divide by mitosis

What are spores

small light asexual reproductive structures that are carried by the wind

Columella

a cross wall pushin up into the sporangium from below + separate spores from the sporangiophores

Apophysis

swelling below the sporangium

Outline the 3 types of hyphae:

Rhizoids - grow down

Stolon - grows across

Sporangiophore - grows up

How does rhizopus normally reproduce + why does it change method?

• normally asexual by sporulation

• sexual reproduction occurs in adverse conditions such as dehydration

Describe asexual reproduction of rhizopus:

• sporangium divides by mitosis to produce haploid cells

• each cell develops a wall and becomes a spore

• sporangium bursts in dry conditions to release spores

• spores dispersed by wind

• germinate if they land on a suitable substrate

Describe sexual reproduction of rhizopus:

• 2 chemically opposite hyphae (+ and -) come into contact

• swellings form and eventually touch

• nuclei move into swellings to form progametangia

• cross walls form behing the progametangia to produce gametangia + block other nuclei from entering

• suspensors support the gametangia

• walls break down between the gametangia allowing the nuclei to fuse to form a diploid zygote

• a tough, black wall forms around the zygote to produce the zygospore

• zygospore germinates by meiosis when conditions are suitable

• hypha grows out of zygospore to produce sporangium, which releases many haploid spoires to produce new hyphae

What is another name for yeast cells?

saccharomyces

Describe the structure of a yeast cell:

• single celled

• round or ovular

• cell walls made from chitin

• has a dense cytoplasm that contains many food storage vacuoles + one large vacuole

• food stored as glycogen

• has one nucleus

How do yeast cells reproduce?

asexually by a process called budding

Describe the process by which yeast cells reproduce

• a small extension called a bud appears on a parent cell

• the parent nucleus divides by mitosis

• one nucleus and some cytoplasm enter the bud

• the bud breaks away from the parent cell or may remain attached

Name 2 economic benefits of fungus:

• mushrooms are a source of food that are sold

• yeast is used for fermentation to produce alcohol and in baking

Name 2 economic disadvantages of fungus:

• can destroy materials such as food, crops and wood

• can cause diseases such as athlete’s foot

What is asepsis?

taking measures to prevent contamination by excluding unwanted organisms, creating a germ free environment - eg. sterilisation

How can asepsis be achieved?

• washing hands before and after

• hair tied back

• disinfect bench before and after

• do not put hands near mouth

• keep all containers closed

What does sterile mean?

all micro-organisms are destroyed

Techniques for sterilisation

• flaming

• swabbing with disinfectant

• immersion in liquid disinfectant