Mushrooms, Molds, and Yeast: Fungal Diversity

What is a fungus?

Eukaryotic heterotrophs that digest food externally by secreting enzymes, then absorb nutrients.

How do fungi digest food?

They secrete enzymes and chemicals outside their cells to break food down before absorbing it.

Are fungi autotrophs or heterotrophs?

Heterotrophs.

Why are fungi important in ecosystems?

They are major decomposers and saprophytes.

What is a saprophyte?

An organism that feeds on dead organic matter.

Why are fungi important in decomposition?

They can digest complex molecules like cellulose and lignin that many animals cannot

What role do fungi play in the carbon cycle?

They break down dead plants and return carbon to the ecosystem.

What are some human uses of fungi?

Food, bread, beer, cheese, and drugs like penicillin.

Are all fungi beneficial?

No. Some are parasites and pathogens.

In what way are fungi similar to animals?

Both are heterotrophs and use glycogen to store energy.

What structural molecule do fungi and animals both produce?

Chitin.

How do fungi differ from plants?

Fungi are heterotrophs, while plants make their own food via photosynthesis.

Do fungi move around?

No, fungi are sessile.

What kind of environment do fungi usually need?

Moist, humid environments.

What are the two main fungal body types?

Yeast and mycelia.

What is yeast?

Single-celled, free-floating fungi.

How do yeast reproduce?

Usually by budding.

What is mycelium?

The multicellular body of a fungus made of hyphae.

What are hyphae?

Thin filaments that form the mycelium.

What do hyphae do?

They penetrate soil, dead organisms, and sometimes living cells to absorb nutrients.

What is a fruiting body?

A reproductive structure, like a mushroom, that disperses spores.

Can some fungi switch between yeast and mycelial forms?

Yes, some fungi are dimorphic.

What are septa?

Cross-walls that divide hyphae into cells.

Are septa completely sealed?

No, they are porous.

What is a coenocytic mycelium?

A mycelium with many nuclei in one continuous cell space, not divided by septa.

What are the six major fungal lineages?

Microsporidia, Chytrids, Zygomycetes, Glomeromycetes, Ascomycetes, Basidiomycetes.

Which fungal group is made of obligate single-celled parasites?

Microsporidia.

Which fungal group produces motile spores?

Chytrids.

Which fungal group forms zygosporangia?

Zygomycetes.

Which fungal group forms arbuscular mycorrhizae?

Glomeromycetes.

Which fungal group includes mushrooms?

Basidiomycetes.

Which fungal group commonly includes lichens?

Ascomycetes.

Do fungi mostly reproduce sexually or asexually?

sexually

How do mycelial fungi commonly reproduce asexually?

By forming sporangia that produce haploid spores by mitosis.

Why are fungal spores useful?

They are more resistant to drying than hyphae.

What is budding?

Asexual reproduction in yeast where a new cell grows off the parent.

What is the first step of sexual reproduction in fungi?

Two compatible mycelia come into contact.

What is plasmogamy?

Fusion of cytoplasm between two hyphae.

What is a heterokaryotic cell?

A cell containing two separate nuclei.

What is karyogamy?

Fusion of the two nuclei into one diploid nucleus.

What happens after karyogamy?

Meiosis occurs to produce spores.

What are microsporidia?

Obligate single-celled parasitic fungi.

What do microsporidia often parasitize?

Fish and invertebrates.

What is hyperparasitism?

Parasitizing a parasite.

What environment are chytrids adapted to?

Wet environments.

What is unique about chytrid spores?

They are motile.

What do chytrids infect?

Plants or amphibians.

Why are chytrids ecologically important?

Some have caused major declines in amphibian populations.

What disease-causing chytrid is famous?

Batrachochytrium dendrobatidis (Bd).

What is alteration of generations in chytrids?

A life cycle with alternating haploid and diploid stages.

Are zygomycetes mostly sexual or asexual?

asexual

What do zygomycetes commonly do?

Digest plants and spoil food.

What structure forms during sexual reproduction in zygomycetes?

Zygosporangia.

What happens in zygosporangia?

Plasmogamy and karyogamy occur there.

What do zygosporangia produce?

Haploid spores by meiosis.

What important drug is linked to fungi from this group in the slide?

Penicillin.

What kind of symbiosis do glomeromycetes form?

Arbuscular mycorrhizae with plants.

Why are glomeromycetes important?

They are important in the terrestrial nitrogen cycle

What are basidiomycetes known for?

Mushrooms and wood-decomposing fungi.

Are basidiomycetes saprophytes or mutualists?

They can be either saprophytes or ectomycorrhizal mutualists.

What nuclear stage is important in basidiomycetes?

Dikaryotic stage.

Why are basidiomycetes ecologically important?

They help with carbon cycling in forests.

Why do humans care about basidiomycetes?

Many are edible mushrooms.

What are common examples of ascomycetes?

Lichens and many fungi that form asci

How do lichens get sugar?

From algae.

What are soredia?

Asexual dispersal structures in lichens.

What is an ascus?

A sexual reproductive structure in ascomycetes.

Where are many lichens especially common?

Arctic and Antarctic tundra.

Why are lichens used as indicator species?

They are sensitive to air pollution.

What does a greater amount and diversity of lichens usually indicate?

Better air quality

What fungus causes white-nose syndrome?

Pseudogymnoascus destructans.

What does white-nose syndrome affect?

Bats.

How severe can white-nose syndrome be?

It can cause 90–100% mortality.

Name a human fungal pathogen.

Candida spp.

Name another human fungal pathogen.

Aspergillus spp.

What fungus causes valley fever?

Coccidioides.

What’s the main difference between yeast and mycelial fungi?

Yeast are single-celled; mycelial fungi are multicellular networks of hyphae.

What is the difference between plasmogamy and karyogamy?

Plasmogamy = cytoplasm fuses; karyogamy = nuclei fuse.

Which fungi form mushrooms?

Basidiomycetes.

Which fungi form lichens most commonly?

Ascomycetes.