Biology II Chapter 29
Gametangia
When hyphae of opposite mating types grow in close proximity, they signal one another with pheromones. In response to these chemical signals, the tips of the hyphae come together and form gametangia, which serve as gametes - Plasmogamy occurs as the gametangia fuse. Then karyogamy occurs as the (+) and (−) nuclei fuse to form the diploid zygote nucleus. The zygote develops into a zygospore
Yeasts
A unicellular fungus (ascomycete) that reproduces asexually by budding or fission, and sexually by ascospores
Conidia
An asexual spore
Endomycorrhizal Fungi
As each hypha pushes forward, the plasma membrane of the root cell surrounds it - Because they penetrate the cell wall, these fungi are referred to as endomycorrhizal fungi
Budding
Asexual reproduction of yeasts is mainly by budding; in this process a small protuberance (bud) grows and eventually separates from the parent cell
What evidence supports the hypothesis that chytrids were the earliest fungal group to evolve from the common ancestor of fungi?
Chytrids, like other opisthokonts but unlike all other fungi, produce flagellate cells at some stage of their life cycle.
Monokaryotic
Hyphae that contain only one nucleus per cell are described as monokaryotic
Fungi Reproduction
Most fungi (but not all) reproduce both asexually and sexually
Heterothallic
The bread mold is heterothallic, meaning that an individual fungal hypha mates only with a hypha of a different mating type (+ with -)
Zoospores
A flagellated motile spore produced asexually by chytrids - Develop into new diploid thalli
Fungi
A heterotrophic eukaryote belonging to the opisthokont clade, with chitinous cell walls and a body usually in the form of a mycelium of branched, threadlike hyphae. Most fungi are decomposers; some are parasitic
Chytridiomycetes
A member of a phylum of fungi characterized by the production of flagellate cells at some stage in their life history. - Chytrids are small, relatively simple fungi that inhabit ponds and damp soil. A few species have been found in salt water - No other fungal group has flagellate cells
Fruiting Bodies
A multicellular structure that contains the sexual spores of certain fungi; refers to the ascocarp of an ascomycete and the basidiocarp of a basidiomycete - The familiar part of a mushroom is a large fruiting body
Primary Mycelium (n)
A mycelium in which the cells are monokaryotic and haploid; a mycelium that grows from either an ascospore or a basidiospore
Fungi Form Symbiotic Relationships with Some Animals
Because animals do not have the enzymes necessary to digest cellulose and lignin, cattle and other grazing animals cannot, by themselves, obtain needed nutrients from the plant material they eat. Their survival depends on fungi that inhabit their guts
Fungi are...
Eukaryotes and Opisthokonts
Zygomycetes
Fungi characterized by the production of nonmotile asexual spores and sexual zygospores. - Most zygomycetes are decomposers that live in the soil on decaying plant or animal matter. Some zygomycetes form a type of symbiotic association (mycorrhizal relationship) with plant roots.
Dikaryotic
Hyphae that contain two genetically distinct, sexually compatible nuclei within each cell are described as dikaryotic (n+n) - The presence of a dikaryotic stage is an important defining character of the ascomycetes and basidiomycetes
Soredia
Lichens reproduce mainly by asexual means, usually by fragmentation, a process in which special dispersal units of the lichen, called soredia break off and, if they land on a suitable surface, establish themselves as new lichens
Ascomycetes
Member of a phylum of fungi characterized by the production of nonmotile asexual conidia and sexual ascospores - include yeasts - In most ascomycetes asexual reproduction involves production of spores called conidia
Ascospore
One of a set of sexual spores, usually eight, contained in a special spore case (an ascus) of an ascomycete
Hyphae
One of the threadlike filaments composing the mycelium of a water mold or fungus. - most fungi are multicellular
Mycotoxins
Poisonous chemical compounds produced by fungi, e.g., aflatoxins that harm the liver and are known carcinogens
Microsporidia
Small, unicellular, fungal parasites that infect eukaryotic cells; classified with the zygomycetes.
Homothallic
Some species of ascomycetes are heterothallic; while others are homothallic, which means that they are self-fertile and have the ability to mate with themselves
In what ways (both positive and negative) are fungi important in modern biology and medicine?
Studies of fungi such as Saccharomyces, Aspergillus, and Neurospora as model organisms have yielded important insights in biology and medicine. Some fungi produce valuable medications, while others are responsible for causing serious diseases.
Basidia
The clublike spore-producing organ of basidiomycetes that bears sexual spores called basidiospores
Basidiocarp
The fruiting body of a basidiomycete, e.g., a mushroom.
Karyogamy
The fusion of two haploid nuclei; follows fusion (plasmogamy) of cells from two sexually compatible mating types.
Gills
The spore-bearing, platelike structures under the caps of mushrooms
Mycology
The study of fungi
Rhizoids
The thallus may have slender extensions, called rhizoids, that anchor it to a food source and absorb food
Mycelium
The vegetative body of most fungi and certain protists (water molds); consists of a branched network of hyphae. - fungi that form mycelia are often called molds
Zygosporangia
The zygospores are typically produced in spore sacs called zygosporangia
Which statement is not true of the chytrids?
Their cells are dikaryotic
Arbuscules
Tree-like branched structures inside root cells produced by hyphae of endomycorrhizal fungi known as glomeromycetes
Opisthokonts
Within the Unikonts supergroup, the clade opisthokonts includes the choanoflagellates, the animals, and the fungi.
Which of the following does not have a mycelium?
Yeast
Ectomycorrhizal Fungi
basidiomycetes also form mycorrhizal connections, but their hyphae coat the plant root rather than penetrate its cells. These species are referred to as ectomycorrhizal fungi.
When a fungus infects a plant, it
enters leaves or stems through stomata
Glomeromycetes...
form arbuscular endomycorrhizae with tree roots
Glomeromycetes
have coenocytic (no septa) hyphae. They reproduce asexually with large, multinucleate spores called blastospores - form Mycorrhizae associations
The ascomycete life cycle typically includes
the production of eight haploid ascospores within an ascus
Which statement is not true of the basidiomycetes?
they have a diploid thallus that produces zoospores
Fungi Digestion
they infiltrate a food source and secrete digestive enzymes onto it. Digestion takes place outside the body
Lichen
A compound organism consisting of a symbiotic fungus and an alga or cyanobacterium - combo of a fungus and a photoautotroph
Secondary Mycelium (n+n)
A dikaryotic mycelium formed by the fusion of two primary hyphae - the two haploid nuclei remain separate within each cell
Chitin
A nitrogen-containing structural polysaccharide that forms the cell walls of many fungi
Spores
A reproductive cell that gives rise to individual offspring in plants, fungi, and certain algae and protozoa.
Asci
A saclike spore case in ascomycetes that contains sexual spores called ascospores
Zygospores
A sexual spore produced by a zygomycete
Sporangia
A spore case, found in plants, certain protists, and fungi
Alternation of Generations
A type of life cycle characteristic of plants and a few algae and fungi in which they spend part of their life in a multicellular n gametophyte stage and part in a multicellular 2n sporophyte stage. - Allomyces, a large, common chytrid, undergoes this
Distinguish among 1. ascocarp, ascus, and ascospore and among 2. basidiocarp, basidium, and basidiospore.
An ascocarp is a fruiting body that produces ascospores (sexual spores) in asci. A basidiocarp is a fruiting body that produces basidiospores (sexual spores) on basidia.
Coenocytes
An organism consisting of a multinucleate cell - the nuclei are not separated from one another by septa
n + n cell means:
Dikaryotic
Basidiospores
Each basidium is an enlarged hyphal cell that undergoes meiosis to form four basidiospores - Note that basidiospores develop on the outside of a basidium, whereas ascospores develop within an ascus.
Rhizopus stolonifer
Familiar zygomycete. Black bread mold
Pheromones
Fungi communicate chemically by secreting signaling molecules called pheromones
Septa
In fungi, the walls that divide a hypha into cells
Haustoria
In parasitic fungi, a specialized hypha that penetrates a host cell and obtains nourishment from the cytoplasm
Plasmogamy
In sexual reproduction the hyphae of two genetically compatible mating types come together, and their cytoplasm fuses
Lichens and Air Quality
Lichens absorb minerals from the air, rainwater, and the surface on which they grow. They cannot excrete the elements they absorb - this is why they are a good indicator of air purity, if the air is too polluted they would die off
Basidiomycetes
Member of a phylum of fungi characterized by the production of sexual basidiospores - include the largest and most familiar of the fungi: the mushrooms, bracket fungi, and puffballs
Thallus
Most chytrids are unicellular or composed of a few cells that form a simple body, called a thallus
Mycorrhizae
Mutualistic associations of fungi and plant roots that aid in the plant's absorption of essential minerals from the soil - improve the soil by decreasing water loss and erosion - occur in about 80% of plants
What are the distinguishing characteristics of each of the following fungal groups: zygomycetes, glomeromycetes, ascomycetes, and basidiomycetes?
Zygomycetes: produce sexual zygospores. Glomeromycetes: sexual spores are large, multinucleate blastospores. Ascomycetes: asci produce sexual ascospores. Basidiomycetes: basidia produce sexual basidiospores.
With the exception of chytridiomycetes, fungi are generally disseminated by
airborne spores
Conidiophores
are specialized hyphae that produce asexual spores called conidia
Which statement is not true of the zygomycetes?
many members of this group form endomycorrhizae with tree roots