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37 Cards in this Set

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What are 5 features distinctive to fungi?
1) The dominant stages have cell walls which are structurally similar to plant cell walls. However, fungi walls are made of CHITIN, plant walls are made of CELLULOSE

2)HETEROTROPHIC eukaryotes. Because of chitonous walls, they have ABSORPTIVE MODE OF NUTRITION. Slime molds are not true fungi, they are PHAGOTROPHIC.

3) Important decomposers (SAPROBES)of plant material b/c they can degrade cellulose and lignin... bacteria can't.

4) Reproduce using walled cells called SPORES

5) Because fungi live in dangerous environments, major organelles are kept back from the apical tip of the hypha
What are LICHENS?
-a symbiotic association of fungi and algae
-extremely hardy (but fragile to pollution)
-survive where few other organismss can
What Kingdoms would you find Fungi in?


Define Hypha
-tubular filaments that represent the structual entity in the majority of the fungi
-a mass of hyphae, with or without septa
What are some distinctive characteristics of yeast?
-unicellular fungi
-have one of two major cell growth forms
-budding mother cells produce an entirely new daughter cell
-FISSION yeast cells grow at each end, and later divide in the middle
How does TIP GROWTH occur in fungi?
-organelle cytoplasm migrates to keep up with the extending tip, and subapical regions are filled with vacuoles to maintain turgor pressure
-apical cytoplasm migrates actively, using Ca+2 regulated actin and myosin contraction to carwl inside the wall tube as the cell grows, leaving vacuoles behind.
-vacuole turgor pressure is to ensure that the older parts of the hypha do not collapse. NOT INVOLVED with hyphal growth in all circumstances
1) Tip growth adds wall material and cell membrane
-most wall material is added near the cell tip, where it contributes to hyphal extension and expansion
-less wall material is added in subapical resions, where it contributes to cell expansion
-wall material is added by EXOCYTOSIS OF WALL FORMING VESICLES which contain wall matrix ad whose membranes contain chitin synthesizing complexes

2)Addition of chtin plus wall maturation produces a gradient of cell wall extensibility, the apex being most extensible
-more chitin is synthesized and crosslinked during wall maturation, especially in the subapical region (making it more rigid)
-water has high surface tension, therefore making it difficult for hyphae to break through
-fungi release the enzyme HYDROPHOBIN into the water medium which drastically reduces the surface tension of water
-this allows the hyphae to excape and grow/sporulate in air
-the aerial hypha continues to secrete hydrophobin, which forms a HYDROPHOBIC RODLET LAYER on the outside of the cell wall
Why are Slime Molds (phagotrophic) classified with fungi?
-the secual stage of slime molds produce spores that have cell walls, a fungal characteristic
-that's all they need to be classified as they are, by all means, they resemble Amoeba way more...
What are the 3 main groups of Slime Molds?
-acellular (Phylum Myxomycota)

-cellular (Phylum Dictyosteliomycota)

-endoparasitic (Phylum Plasmodiophoromycota)
What are some defining characteristics of slime molds?
-AKA The Acellular Slime Molds
-the 'cell' (or PLASMODIUM) is equivalent to the whole organism
-can be larger than a dinner plate
-contain countless millions of muclei in their plasmodia
-nuclei move in a coordinated fashion, back and forth (SHUTTLE STREAMING), through vein like strands which appear to organize the myxomycete body
-mitotic cycle of the nuclei is synchronous throughout the cell
Go over the life cycle of an acellular slime mold.
-2n spores are formed within the sporangia and undergo meiosis as the sporangium matures
-3/4 nuclei degernerate leaving 1 haploid nucleus per spore
-spore germinates to produce a single HAPLOID BIFLAGELLATE SWARM CELL (amoeboid) -OR- the spores may give ise to HAPLOID NON-FLAGELLATE AMOEBA (MYXAMOEBA) which may become flagellate later on
-those shits fuse, undergo growth and nuclear divisions, producing a variable sized, 2n multinucleate plasmodium
-plasmodium may form SCLEROTIUM or it may sporulate
-process repeats
List some of the complex behaviors displayed by Myxomycete.
-plasmodium does not return along its own path where some of the slimy sheath is left behind
-mycomycetes can recognize compatible vs. incompatible plasmodia, and respond accordingly
When does plasmodium form fruiting structures?
-nutrients are exhausted
-under the proper temperature, humidity and light
How are fruiting structures formed on plasmodium?
-many can fruiting structures can be formed by one plasmodium
-they may either be stalked or sessile
-differ greatly in structure in different orders

-protoplasm of the plasmodium flows towards the points where fruiting structures will form
-small nodules result, which grow upwards as they increase in syze
-once they have the shape of the fruiting structure, the nuclei acquire portions of cytoplasm
-meiosis creates uninucleate, haploid mature spores
-the spore mass is enclosed b a thin wall, the PERIDIUM, which is reinforced by threads called the CAPILLITIUM in some species
-Stemonitis sporangium has a central core, the COMLUMELLA
What are some distinguishing characteristics of the Phylum Dictyosteliomycota?
-AKA the Cellular Slime Molds
-composed of cells
-can be isolated MYXAMOEBAE, which may form an agregate, superficially resebling a myxomycete plasmodium, called a PSEUDOPLASMODIUM

-difference is in cellular slime molds, myxamoebae remain as distinct cells withing the pseudoplasmodium, and later in their fruiting structures.

-sexually and asexually produced spores germinate to produce uninucleate haploid myxamoebae
-these move using pseudopodia, and feed on bacteria by phagocytosis
-during feeding phase, myxamoebae divide mitotically (type of asexual reproduction)
-they are attracted by bacteria over distances of approx 1.5mm, but are repeled by each other
-once food supply is exhausted, the behavior changes and they become attracted towards each other...
-this is the AGGREGATION PHASE (dealt with in another card)
-common to phylum Dictyosteliomycota
-begins when food supply is exhausted and cells become attracted to eachother
-cells begin to migrate towards one or a few cells, which act as foci
-isolated cells are attracted directly, with more distant cells joining to form streams, and moving towards the focus in a coordinated way
-gocal cells secrete rhythmic pulses of cyclic adenosine monophosphate (cyclic AMP - which is a cell signaling molecule in all eukaryotes) which are detected and remplified until a large population of isolated cells has united, forming a PSEUDOPLASMODIUM (AKA - GREX)
-a grex resembles a tiny slug
-it migrates as a single entity
-the tip cells direct the movement of the whole aggregate
-they are sensitive to light as well as othr environmental factors
-in contrast to myxomycetes, pseudoplasmodia DO NOT FEED, therefor have limited life span (hours-days)
Go over the life cycle of Dictyosteliomycota.
-exist as individual cells
-unite into a non-feeding entity called PSEUDOPLASMODIUM (AKA GREX)
-migrates as a whole to a different location
-once migration stops, the grex forms a fruiting structure called a SOROCARP, consists of a stalk and a mass of spores called a sorus
-the stalk beigins to form first and the amoebae destined to become spores creep up the developing stalk
-FOOT CELLS at the base come from the same population as spore cells
-unlike myxomycetes, there are no nuclear divisions after pseudoplasmodium formation
-until midway in sorocarp formation, these cells are not truly differentiated
-a change in environment, such as additional food, spores germinate and release individual myxamoebae
-spores and stalks have cellulose containing walls

-myxamoebae aggregate to form a MACROCYST
-karyogamy occurs in the macrocyst
-this is the only diploid part of the life cycle, and is lacking in some species
-meiosis occurs before germination, resuting in haploid myxamoebae

**pg. 94**
What are some defining characteristics to the Phylum Plasmodiophoromycota
-intracellular parasites of vascular plants, as well as algae and aquatic fungi
-produce anteriorly flagellate cells, which become amoebe when they penetrate the host cells
-best known representative is Plasmodiophora brassicae (cause of clubroot disease, increased cell division as well as abnormal enlargement [hypertrophy])
Go over the life cycle of phylum Plasmodiophoromycota.
-spores germinate to produce flagellated cells and these change into amoebae
-amoebae penetrate throught the root hairs into the epidermal cells of the host where they grow into multinucleate plasmodia
-some plasmodia form gametes which fuse via PLASMOGAMY giving rise to a secondary plasmodium (n+n) which infects the cortical cells of the host root
-after KARYOGAMY and meiosis, these plasmodia may also give rise to haploid resint spores that have thick walls containing chitin
-these spores clump together as so called SPORE BALLS in the host cells
-resting spores are released when the host cell breaks down, and eah spore produces a uninucleate zoospore
-zoospores eventually reinfect another host

What are some defining characteristics to the Phylum Oomycota
-belongs to the Kingdom Chromista (most commonly known for algae)
-AKA Water Molds
-have heterokont flagellation, therefor strongly related to algae of Chromista
-grow by tip growth in the vegetative stage
-hyphal walls contain cellulose, but otherwise their growth mechanics are similar to hyphae of the Eumycota, whose walls have chitin
-are aseptate, except reproductive cells, which have complete (APERFORATE) septa
Go over the life cycle of Saprolegnia
-attacks weakened fish
-reproduce asexually by 2 types of motile zoospores which are formed in the zoosporangia
-Saprolegnia has both primary and secondary zoospores that have heterokont flagella, tinsel and whiplash
-primary zoospores have their flagella both inserted at the anterior of the cell
-they are poor swimmers which soon lose their flagella and encyst
-primary cysts germinate to produce secondary zoospores, whose flagella are inserted laterally
-secondary zoospores encyst and have spiny projections surrounding it
-either primary or secondary cysts can germinate to produce a hypha, given a relatively rich environment
-hypha grows and may regenerate sporangia, cycle repeats

-sexual reproductive organs are the male ANTHERIDIUM and the female OOGONIUM, which contains one to several haploid eggs called OOSPHERES (usually occur at the tips of special hyphal branches and are separated by a septum from these hyphae)
-branch tips DO NOT differentiate into gametangia until the septum is formed
-meiosis occurs in the oogonium and antheridium
-antheridium grow toward and around the oogonia and then produce FERTILIZATION TUBES, which penetrates the oogonium wall and fuses with the oosphere
-a haploid nucleus passes through the tube to each oosphere and combines with its nucleus via karyogamy
-after fertilization, a thick wall forms around each oosphere and it becomes the diploid OOSPORE
-the male and female gametangia may form on the same mycelium (derived from one spore and called HOMOTHALLISM) or on separate mycelia (HETEROTHALLISM)
-Oospores are eventually released and germinate

What are the functions of spines on Secondary cysts of Saprolegnia?
-may aid attachment to water meniscus
-may aid attachment to host
-reduces sedimentation rate

**pg.99 & 100**
What are some defining characteristics to the Order Peronosporales?
include some of the most destructive of all plant pathogens:
-Pythium debaryanum = damping off disease of seedlings
-P. insidiosum has been identified as a human pathogen
-Albugo spp's are white rusts that attack cultivated plants particularly in the cabbage family
-Peronspora, Plasmopara and related genera are downy mildews
-Phytophthora = late potatoe blight

-when we look at asexual reproduction in the Peronosporales, we see a transition from an aquatic to a terrestrial mode of life, which is critical to this groups success as plant pathogens

-sexual reproduction is like Saprolegniales, but the oogonium contains only one oosphere

-at high temp, sporangia germinate directly by a germ tube which penetrates the host tissues
-at low temp, it can form zoospores, which swim in the film of dew on the leaves and eventually encysts and form germ tubes
What is Phytophthora infestans?
-the cause of the LATE BLIGHT OF POTATOE
-can kill aerial parts of susceptible potatoes within a week and, while it does not affect the tubers at this stage, it is a rapid and efficient saprobe once tubers are harvested
What are some defining characteristics to the Kingdom Eumycota?
-AKA True Fungi
-have chitin in their cell walls therefore must feed by absorption
-have non-motile reproductive cells (except for chytrids)
What are some defining characteristics to the Phylum Chytridiomycota
-may have spp's that have ALTERNATION OF GENERATIONS which is rare in fungi
-haploid and diploid phases may be ISOMORPHIC which further confuses shit
Go over the life cycle of Allomyces.
-a haploid mycelium produces adjacent male and female gametangia, which release gametes that fuse to produce motile diploid zygotes (zygospores)
-the zygote settles on a substrate, forms a diploid mycelium and this produces sexual THICK WALLED RESISTANT SPORANGIA and asexual THIN WALLED SPORANGIA

-in the thick walled sporangia, the nuclei undergo meiosis and haploid zoospores emerge
-they germinate and form HAPLOID MYCELIA
-the thin walled sporangia form DIPLOID ZOOSPORES which regenerate DIPLOID MYCELIA asexually
-the resistant sporangia can survive drying for long periods and zoospores from thin walled sporangia rapidly mulitply the diploid phase

**M1-7,8,9 & drawings pg.3**
Go over the generalized life cycle of Chytrids
-have a relatively simple life cycle
-infects a green alga
-eventually produces a large thallus (multicellular body) that develops into a diploid zoosporangium from which zoospores are released
-process repeats

**pg.102, 103**
Classify, draw and label Physarum
P-Myxomycota (acellular slime molds)

Did you get:
Classify, label and draw Stemonitis.

Did you get:
What Kingdom would you find Phylum Dictyosteliomycota (cellular slime molds)?
Kingdom Protista
Classify, label and draw Plasmodiophora
P-Plasmodiophoromycota (endoplasmic slime molds)

Did you get:
-healthy host root parenchyma cells
-invaded host cells
-resting spores
Classify, label and draw Achlya
P-Oomycota (water molds)

Did you get:
Classify, label and draw Saprolegnia
P-Oomycota (water molds)

Did you get:
Classify, label and draw Allomyces
K-Eumycota (True Fungi)
P-Chytridiomycota (flagellate fungi)

Did you get:
-hypha with a pair of gametangia
-male gametangium
-female gametangium
-discharge papilla
-male gametes
-female gametes
-germinating zygote
-thick walled resistant sporangium
-thin walled sporangium