Fungi

heterokaryon

A mycelium containing coexisting, genetically different, haploid nuclei.

Chitin

A strong but flexible polysaccharide that makes up the fungal cell wall.

What are some of the dangers fungi present to humans?

About 30% of known fungal species are parasites or pathogens, mostly on or in plants. Some fungi that attack food crops are toxic to humans. Essentially, fungal infections can be dangerous. For instance, fungal respiratory infections like aspergillis or pneumonia are very unpleasant but are more common in the immunocompromised.

Why are mycorrhizae important?

Almost all vascular plants have them and rely on them for essential nutrients.

How does the chitin-rich cell wall facilitate fungal feeding?

As fungi absorb nutrients from the environment, the concentrations of those nutrients in its cells increase, causing water to move into cells by osmosis. The movement of water would cause fungal cells to burst if not for the rigid cell wall of chitin.

conidia

Ascomycetes reproduce asexually by producing enormous numbers of these asexual spores which are dispersed by wind

How do fungi typically asexually reproduce?

By growing as filamentous fungi that produce haploid spores by mitosis. These are generally called molds. By growing as single-celled yeasts. Instead of producing spores, reproduction occurs by ordinary cell division or the pinching of small bud cells off a parent cell.

What are the general characteristics of phylum Ascomycota?

Called the sac fungi due to their saclike asci, which produce spores. (conidia) Has asci; sacklike spore capsule loacated at the tip of a dikaryotic hypha of a sac fungus. Ascomycetes reproduce asexually by producing enormous numbers of asexual spores called conidia.

What are the general characteristics of the phylum Basidiomycota? (5)

Club-shaped bastidium, a cell in which karyogamy and meiosis occur ("club fungus"). Mostly saprobes but also some plant parasites and plant mutualists. Good at breaking down wood. No typical asexual stage. In response to environmental stimuli, the mycelium reproduces sexually by producing elaborate fruiting bodies called basidiocarps.

Septa

Cross-walled divisions in hyphae that have pores large enough to allow ribosomes, mitochondria, and even nuceli to flow from cell to cell.

How do fungi obtain energy?

Fungi are heterotrophs who use hydrolytic exoenzymes to digest their food before ingesting it. The absorptive mode of nutrition is associated with the ecological roles of fungi as decomposers(nonliving), parasites, and mutualists.

Though fungi are not motile in the typically sense, how are they able to move?

Fungi can grow into new territory by extending the tips of their hyphae. Essentially, fungi will grow into new territory.

Coenocytic fungi

Fungi that lack septa. These organisms consist of a continuous cytoplasmic mass having hundreds or thousands of nuclei.

What are the general characteristics of phylum Chytridiomycota?

Have a flagellated stage called a zoospore (unique to this phylum). Mostly aquatic saprobes and parasites.

hetero vs dikaryotic

Heterokaryotic refers to cells where two or more genetically different nuclei share one common cytoplasm. Dikaryotic is having two different and distinct nuclei per cell

What are some of the benefits humans derive from fungi? (3)

Humans eat many fungi and use others to make cheeses, alcoholic beverages, and bread. Some fungi are used to produced antibiotics -- penicillium Genetic research on fungi is leading to applications in biotechnology; for instance, insulin-like growth factor can be produced by a certain type of fungus.

karyogamy

Karyogamy is the fusion of the two parent nuclei, which were brought together during plasmogamy. This forms a diploid cell, as well as zygotes and other transient structures

What are lichens?

Lichens are mutualistic relationships between green algae and fungi in which millions of photosynthetic cells are held in a mass of fungal hyphae.

What are the general characteristics of the phylum Zygomycota? (2)

Mainly terrestrial saprobes The hyphae are coenocytic, with septa found only where reproductive cells are formed

What happens after karyogamy?

Meiosis restores the haploid condition, ultimately leading to the formation of genetically diverse spores. Spores produced in this way are called sexual spores.

What are mycorrhizae?

Mutually beneficial relationships between fungi and plant roots.

How do mycelia help fungi grow so quickly?

Not only is the structure of the mycelium well-suited for growth, the fungus will concentrate on adding hyphal length and thus overall absorptive surface area by streaming proteins and other synthesized materials into the tips of extending hyphae.

What key characteristics define fungi? (5)

Nutrition and energy: heterotrophs who digest food before ingesting it; made up of saprobes, parasites, and mutualists. Body structure: Multicellular filaments and single cells together; form a network of tiny filaments called hyphae; have a cell wall made of chitin Non-vascular Reproduce using sexual or asexual spores Typically non-motile

haustoria

Parasitic fungi usually have specialized hyphae called haustoria, nutrient-absorbing hyphal tips that penetrate the tissues of their host. found in most fungi

General: What are the steps of fungal sexual reproduction? (6)

Pheremones signal the presence of a nearby mating fungus. Hyphae meet and fuse, undergoing a compatibility test. Plasmogamy. Karyogamy Meiosis Germination

What occurs during plasmogamy?

Plasmogamy is the union of cytoplasms of two parent fungi. In most fungi, the haploid nuclei contributed by each parent do not fuse right away. Instead, parts of the fused mycelium contain coexisting, genetically diffeerent nuclei.

Yeasts

Single-celled fungi that often inhabit moist environments such as animal tissues where there is a ready supply of soluble nutrients like sugars and amino acids. non filamentous

zygosporangium

Specialized spores that are resistant to freezing and drying and are metabolically inactive. formed by plasmogamy

Give the hierarchy of the ascomycetes reproductive structures.

Spores are called ascospores. Ascopores are contained within the saclike asci. Asci are contained within fruiting bodies called ascocarps.

How does the structure of the mycelium aid in growth?

The structure of mycelium maximizes its surface-to-volume ratio, making feeding very efficient. Just 1 cm3 of rich soil my contain as much as 1 km of hyphae with a total surface area of 300 cm2 in contact with the soil.

What do mycorrhizae do?

They improve delivery of nutrients because the vast mycelial networks of the fungi are more efficient than the plants' roots at acquiring minerals from the soil. In exchange, the plants supply the fungi with organic nutrients such as carbohydrates.

What do mycelia do?

They infiltrate the material on which a fungus feeds.

How do fungi signal mating?

They use pheremones, which are sex-signaling molecules. If the mycelia are of two different mating types, the pheremones from each partner bond to receptors on each other, and their hyphae extend toward the source of the pheremones.

Why are deuteromycetes not a true phylum?

This group contains all fungi with no known sexual stage. Once a sexual stage is discovered, the fungus is then reclassified into its appropriate group.

Hyphae

Tiny filaments that make up the multicellular mycelia, consisting of a tubular cell wall surrounded by the plasma membrane and cytoplasm of the cells.

What are the general characteristics of the phylum Glomeromycetes? (2)

Typically plant symbionts, which form a distinct type of endomycorrhizae called arbruscular mycorrhizae that extend into plant cells and expand into a brushlike structure

dikaryotic

occurs when haploid nuclei pair off two to a cell in a mycelium As a dikaryotic mycelium grows, the two nuclei in each cell divide in tandem without fusing.

mycelia

the vegetative part of a fungus or fungus-like bacterial colony, consisting of a mass of branching, thread-like hyphae