Chapter 31 - Fungi Flashcards
Fungi are most related to what kingdom?
Animals
What substance is found in the cell walls of fungi? And is also found in what other organisms?
• chitin
- found in exoskeletons of arthropods
Hyphae
Individual filaments in the body of the fungus
Mycelium
A mass of connected hyphae in the body of the fungus
Monokaryotic
- (separate)
* hyphae w/one nucleus
Dikaryotic
Hyphae w/2 nuclei
Heterokaryotic
Nuclei from 2 genetically distinct individuals
Homokaryotic
Nuclei from genetically similar individuals
Coenocytic
Hyphae made up of a continuous cytoplasmic mass w/hundreds or thousands of nuclei
What is the relevant unit of reproduction in fungi?
The nucleus; not the cell
How do fungi take in nutrients?
- heterotrophic
* excrete enzymes for external digestion and then absorb digested products (saprobic)
How does sexual reproduction occur in fungi?
- involves fusion of hyphae from 2 compatible mating types or hyphae from the same fungus
- compatibly is determined by pheromones released by hyphae
Plasmogamy
Union of the cytoplasms of two parent mycelia followed by
Karygomy
Fusion of haploid nuclei from the parent mycelia; produces diploid nucleus
How do fungi reproduce asexually?
- spores spread; dispersed by wind
* yeast (unicellular example) can reproduce by budding
Features of chytridiomycota
- fungi w/flagellated zoospores
- aquatic, flagellated fungi
- can be plant pathogens
- can be parasites of other fungi, protists, and animals
Chytrids have been implicated in the die-off of what organisms around the world?
Amphibians
Key characteristics of zygomycota
- produces zygotes
- Rhizopus found growing in moist bread or fruit
- the simple type feeds on sugars
Sexual Reproductive cycle of Rhizopus
- plasmogamy produces a sturdy structure called a zygosporangium
- karyogamy entails fusion of haploid resulting in diploid zygote nuclei
Asexual reproductive cycle of Rhizopus
- more common
* sporangia release thin-walled haploid spores which may be dispersed by wind
Characteristics of Glomeromycota
- can not survive w/out a host plant
- mutualism is involved where the fungus provides minerals (especially phosphorus) to the plant and the plant provided carbohydrates to the fungus
- grows within root cells of most trees & herbaceous plants; these hyphae are called arbuscular mycorrhizae
Characteristics of Ascomycota
- make up 75% of known fungi
- examples include yeast, common molds, morels, cup fungi, and truffles
- this phylum also includes plant pathogens such as those that cause chestnut blight and Dutch elm disease
How do yeasts reproduce?
Cell fission or budding
Characteristics of basidiomycota
- visible reproductive structure = basidiocarp
- EX. Mushrooms, toadstools, puffballs, shelf fungi (breaks down lignin in wood), etc
- sexually reproduce w/basidia; gills on the undersurface of the mushroom cap produce numbers of spores
What 2 substances are fungi able to breakdown
Lignin and cellulose which then releases carbon, nitrogen, and phosphorus resulting in making these elements available to other organisms
Obligate Symbiosis
- essential to survival
* they have to have that relationship w another organism to live
Facultative symbiosis
• fungus can survive w out a host
Pathogen
- fungus benefits and host is harmed or killed
* they can cause disease
Parasite
- fungus benefits and host is harmed or killed
* does not cause disease except in extreme situations
Commensalism
• only one partner benefits and the other is unaffected
Mutualism
• both the fungus and host benefit
Endophytes
- live inside plants and may protect them from parasites
* some produce chemical toxins or other deterrents to keep things away
Lichens
- are an example of symbiosis
- composer of a fungus (usually ascomycete) along w/Cyanobacteria, green algae, or both
- can live in very harsh habitats
- usually the first to colonize an area
- break down rocks and help prepare for invasion of other organisms
- produce bright pigments (some used as dyes)
- some are used to indicated air quality as they can absorb rain and dew
- few are found in or near cities and as pollution decreases, their population increases
Mycorrhizae
- Associated w/roots of plants
- means fungus roots
- fungal hyphae increases amount of contact w/soil & surface area for absorption
- aid in direct transfer of phosphorus, zinc, copper, and other minerals
Haustoria
Specialized hyphae used to extract from or exchange nutrients w plant host
Arbuscular Mycorrhizae
Grow within the outer cells of the plant root
Ectomycorrhizae
Surround root cells but do not penetrate them
Examples of symbiosis between fungi and animals
- ruminant animals have fungi in their gut
* ants provide food for fungi and then eat fungi
Fusarium
- grows on spoiled food
* produces vomitoxin that can cause brain damage in animals/humans in sw us
Aspergillus
- Produces aflatoxins that are very carcinogenic (cancerous)
- strains are on corn, peanuts, cotton seeds
- can damage kidneys & nervous system
- considered a bioterrorism agent
Corn smut
Damages corn but is not harmful to animals or humans that consume it
Ergot
- fungus associated w rye and other cereal grains
- an alkaloid toxin is produced & if eaten can cause hallucinations, nervous spasms, gangrene, and burning sensations
- lysergic Avis has been isolated from ergot and is used to make LSD
- implicated Salem witch trials
Why are fungal infections difficult to treat?
They are eukaryotes and antibiotics cannot be used to treat them
Examples of fungal diseases
- ringworm
- athletes foot
- thrush
- nail fungus
- oral or vaginal infections caused by candida
- mold allergies
