Ch. 24 Fungi Flashcards
Several characters were originally used to unite and define fungi:
- complete heterotrophy with no photosynthetic stages
- formation of spores
- the presence of chitin in their walls
- lack of complex bodies with organs
All fungi are completely ___
Heterotrophic
Fungi must obtain
Soluble nutrients from the environment or from living, dying, or dead organisms
Fungi are subdivided into three groups:
Biotrophs, necrotrophs, and saprotrophs
Biotrophs
- parasites
- draw nutrients slowly from living hosts, often without killing them
Necrotrophs
Attack living hosts so virulently that they kill the hosts and then absorb released nutrients
Saprotrophs
Attack organisms after they have died from other causes
Extracellular digestion
Secrete digestive enzymes that attack host polymers, converting them to sugars, amino acids, and lipids that can be absorbed
Fungi, along with most bacteria, are agents of..
Decay, rot, spoilage, and decomposition
Necrotrophs secrete ___ that kill host cells
Toxins
Excessive levels of ___ are involved in many fungus-induced diseases
Plant hormones
Plant hormone may be produced and secreted by the fungus, or
The fungus induces the plant to produce increased levels of its own hormones
Many plants produce ___, lipid-like or phenolic compounds, in response to attack by fungi, bacteria, and even nematodes.
Phytoalexins
The common essential microelements are
Iron, zinc, copper, manganese, molybdenum, and either calcium or strontium
Virtually all fungi absorb and assimilate ___
Ammonium
The bodies of all fungi, except unicellular ones, are ___
Filamentous
Hyphae
Individual filaments
Mycelium
Hyphae branch profusely, forming this network
Fungal cells are ___
Eukaryotic
The innermost cell wall later is rich in ___, which provides strength
Chitin
At one time, ___ and ___ were considered parts of the plant kingdom
Fungi and bacteria
An important aspect of hyphal walls is the nature of the ___ or __
Cross walls or septa
The primary selective advantage of septa appears to be what rather than compartmentalization of hyphae into distinct cells?
Damage control
Fungal nuclei are extremely ___
Small
___ in most species of fungi is very uniform, showing little differentiation into euchromatin and heterochromatin
Chromatin
During mitosis, the spindle forms inside the nucleus, which remains quite distinct because ..
The nuclear envelope does not break down as it does in plants and animals
During ___, the nucleus elongates and the nuclear envelope stretches
Anaphase
In some species, the nucleolus is ejected from the nuclear during ___, whereas in others, or remains intact and passes to one of the new nuclei
Prophase
In ascomycetes and basidiomycetes, but not in the other fungi, some mycelia form a large, compact, highly organized structure called a ___ which is the principle means of producing spores sexually
Fruiting body
The outermost surface hyphae are often slender and have thick walls impregnated with pigments called ___
Melanins
Within large fruiting bodies, especially bracket fungi, are three types of hyphae:
- generative hyphae
- skeletal hyphae
- binding hyphae
Generative hyphae
Thin walled and produce spores
Skeletal hyphae
Thick wall and unbranched
Binding hyphae
Thick walled but are highly and irregularly branched
A universal character of fungi is their formation of ___, resistant resting stages that are the primary means of reproduction, dispersal, and survival
Spores
Spores are produced __ and ___
Asexually and sexually
In zygomycetes, asexual spores are typically ___
Sporangiospores
Sporangiospores
Spores that form inside the large swollen tip of a hypha
In ascomycetes, basidiomycetes, and deuteromycetes, asexual spores are more often produced as ___
Conidia
Conidia
Spores that do not form inside a sporangium
Sexual reproduction in most fungi
Hyphae of one mycelium fuse with hyphae of a different mycelium if the two are compatible; these are opposite mating types, designated as + and -
Plasmogamy
The fusion of two hyphae
Plasmogamy is usually not followed immediately by ___
Kayogamy
Karyogamy
Doesn’t occur ultimately, in a special reproductive structure characteristic of each clade
Although fungi are rather simple morphologically, they are diverse in their ___, ___, and ___.
Metabolism, energy, and life cycles
Many fungi are capable of either ___ or ___ growth
Aerobic or anaerobic growth
As with bacteria, some fungi are extreme ___, growing best at temperatures up to 50C but poorly at or below 20C.
Thermophiles
___ fungi are those that grow best in cold conditions, in the range of -10C to -15C
Psychrophilous fungi
___ fungi grow on “dry” substrates, dryness being due to no lack of water but instead to a high concentration of solute or other materials that bind waters firmly
Xerophilous
___ are distinct from true fungi
Slime molds
In true slime molds, the body is a large mass of ___ containing thousands of nulei, all in the same cytoplasm
Protoplasm
This mass of protoplasm, called a ___, is capable of migrating over a substrate, but is so large that it is easily visible to the naked she o
Plasmodium
Most ___ have chitinous walls like other fungi, but they are distinct in having ___.
- Chytridiomycetes
- flagellated motile cells
All groups are primarily ___, with most species living in streams, ponds, or lakes
Water molds
___ live on various substrates, some being parasitic on other water molds and algae and others saprotrophic on dead insects and plant parts
Chytrids
Zygomycetes
- approx 600 described species
- most are terrestrial and live in decaying plant and animal matter in soil or forest litter
- mold on stale bread, Rhizopus stolonifer
- simple mycelia composed of branched coenocytic hyphae; complex fruiting bodies were not formed
- sexual production occurs in zygomycetes if hyphae of one individual come close to those of another of compatible mating strain
Zygomycetes are characterized by their method of sexual reproduction, which results in..
A large zygosporangium with mandate dormant nuclei
Ascomycetes
- all have asci
- thought to have evolved from a zygomycete-like ancestor
- form ascocarp
Asci
Large sac-like cells in which Karyogamy and meiosis occur and in which the resulting meiospores form
Ascocarp
A rather organized, pseudo-parenchymatous fruiting body
Ascomycetes asexual reproduction occurs by..
Formation of Conidia
Sexual reproduction in ascomycetes
Two compatible hyphae that happen to approach each other each produce special short, multinucleate branches: ascogonium and antheridium
- nuclei pair but do not fuse (dikaryotic)
- no sperms, eggs, or zygotes, but syngamy, meiosis, and crossing-over do occur
Ascocarps of three types:
- the cleistothecium is spherical with no opening; spores are released upon decay
- a perithecium is a flask-shaped ascocarp that releases ascospores through a narrow opening
- apothecia are disk or saucer shaped
Basidiomycetes
Mushrooms, puffballs, and bracket fungi
- delimited by a synapomorphy, the basidium
Basidium
Terminal cell of a reproductive hypha of a basidiomycete; in it, the two compatible nuclei fuse and then immodestly undergo meiosis and crossing-over
Basidiospores do not form inside the basidium, however; instead four tiny projections form, called ___
Sterigmata
Imperfect fungi
- deuteromycetes
- able to persist indefinitely using only asexual means of propagation
- artificial classification
____ has made it possible to examine the structure of their septa
Electron microscopy
Lichens
Association of a fungus with an alga or a cyanobacterium
- symbiotic
Symbiotic relationship
Each organism benefits
Soredia
Small masses of hyphae and autotrophic cells
Mycorrhizae
Symbiotic association of roots and soil fungi
Fungus-plant association occurring in orchids
Appears as if the orchid is parasitizing the fungus because the fungi are capable of living freely without the orchid
Fungi mostly interact with living plants as ____
Disease organisms
Brown rot of stone fruits
Peaches, plums, and cherries are attacked by the ascomycete Monilinia fructicola which causes brown rot
- after Conidia germinate, hyphae invade the fruit, dissolve the middle lamella, and cause tissues to become soft and brown
The fruit finally rots and shrivels, becoming a ___
Mummy
Rusts and smuts
- serious plant diseases caused by basidiomycete
- rusts (order Uredinales)
- smuts (order Ustilaginales)
- can attack hosts so virulently that they kill the plant
- most notorious species is the stem rust fungus Puccinia graminis, which occurs in many forms
The life cycle of P. Graminis is..
Complex but excellent for understanding many aspects of fungal biology
- heteroecious species
- this life cycle has the basic features of basidiomycetes, plus some additional ones
Heteroecious species
It requires two different living hosts to complete its life cycle
