42 terms

Bio Ch 17 fungi

STUDY
PLAY
Mycorrhizae
root fungus associations that enhance the uptake of water and minerals by the plant and provide organic nutrients to the fungus; helped make the colonization of land possible; connection with plants probably also helped fungi make the move onto land.
fungi
heterotrophic; cannot make their own food molecules and must obtain them from other organisms. Fungi may have thrived only in aquatic environments before plants colonized land and began stocking soil with organic molecules.
today fungi
abound in the soil and aquatic environments; some are parasites
80%
of plant diseases are caused by fungi
decomposers
many fungi decompose dead organisms. Essential to all forms of life because they restock the environments with inorganic nutrients essential for plant growth.
fungi
absorb food after digesting it outside their bodies
Classified in
kingdom Fungi
what are fungi
heterotrophic eukaryotes that acquire their nutrients by absorption. most multicellular
absorption
they secrete powerful enzymes that digest their food externally and then absorb the small nutrient molecules.
yeasts
unicellular fungi but their simple structure probably evolved from mulitcellular ancestors
hyphae
thin filaments that branch repeatedly; actually grow into the cells of the leaf and digest the cytoplasm; surrounded by a plasma membrane covered by a cell wall
mycelium
feeding network formed by branches of hyphae
mushroom
an above ground reproductive structure attached to a much more extensive underground mycelium
cell walls
made of chitin, a strong flexible polymer of a nitrogen containing sugar
hyphae
secrete enzymes that digest plant cell walls and then grown into them. It's tips are just the right size and shape to invade plant cells or grow between them
non motile
do not move about in search of food or mates; do not have flagellated or amoeboid cells at any stage; makes up for lack of mobility by growing at a phenomenal rate, branching throughout a food source and extending its hyphae into new territory
dikaryotic phase
third phase in which the cells contain two distinct haploid nuclei
cycle of a mushroom step 1
mushroom itself is called a fruiting body; it consists of tightly packed dikaryotic hyphae
step 2
numerous specialized cells are produced on the underside of the mushroom cap; these terminal cells are the only diploid stage in the life cycle; each cell contains a diploid nucleus resulting from fusion of 2 haploid nuclei; each diploid cell undergoes meiosis and haploid spores are formed
step 3
the mushroom releases enormous numbers of these spores; carried by wind, animals, the spores may land on moist matter that serve as food
step 4
they germinate and grow into haploid mycelia
mating types
discrete kinds of haploid mycelia; contain genetically distinct nuclei and only certain types are sexually compatible
step 5
dikaryotic stage begins when hyphae of 2 compatible mycelia grow together; hyphae fuse but not the nuclei
step 6
results in a dikaryotic mycelium; each of its cells contain two genetically different nuclei
fruiting body
extension of the dikaryotic mycelium and cells making up the fruiting body are dikaryotic
retains genetic variability
dikaryotic fruiting bodies lead to the formation of genetically different kinds of mycelia; fungus retains genetic variability and its capacity to adapt to the changing conditions of its environment; increases the number of organisms enormously
lichens
associations of millions of green algae or cyanobacteria held in a tangled network of fungal hyphae; resemble mosses and other simple plants; mutualistic merger so complete that lichens are actually named as species, as though they were individual organisms
lichen association
fungus is known to receive food from its photosynthetic partner; the fungal mycelium in turn provides a suitable habitat for the algae, helping to absorb and retain water and minerals
lichen fungi
cannot survive on their own
survive in inhospitable habitats
lichens are able to live where there is little or no soil; important pioneers on new land; grow into tiny rock crevices, adding to forces that erode hard surfaces and paving the way for future plant growth
can withstand
severe cold, severe drought, absorbs water and photosynthesizes at a rapid rate when raining; dehydrates and photosynthesis may stop in dry air, but the lichen remains alive more or less indefinitely
do not withstand
air pollution very well; get most of minerals from the air, lichens are very sensitive to airborne pollutants such as sulfur dioxide; death of lichens may be a sign that air quality is deteriorating
parasites
fungi that infect plants have literally changed landscapes; cause Dutch elm disease
agricultural pests
smuts and rusts are common on grain crops and cause tremendous economic losses each year
attack food crops
toxic to humans. seed heads of grain are sometimes infected with fungal growths called ergots. animals less susceptible to parasitic fungi than plants are
mycosis
general term for a fungal infection
opportunistic pathogen
a normal inhabitant of the body that grows out of control when there is a change in the body's microbiology, chemistry, or immunology
dependent on fungi
as decomposers and recyclers of organic matter
unicellular fungi, yeasts
used in baking, brewing, and winemaking
medical
valuable medically, some fungi produce atibiotics that are used to treat bacterial diseases.
penicillin
first antibiotic discovered, made by the common mold called penicillium
fungi are vital contributers to the world
producers of antibiotics and food, decomposers and as mutualistic partners in mycorrhizae and lichens