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Biology 2014-2015

Funguslike Protists

SWS Biology
SWS Life Science

Section 20-5 


Slime Mold


Slime Mold 

Funguslike Protists

    heterotrophs that absorb nutrients from dead or decaying organic matter

    lack chitin in their cell walls

    Three types:

       cellular slime molds

       acellular slime molds

       water molds


Slime Molds

    funguslike protists that recycle organic material

    found on forest floors or a backyard compost pile

    at one stage in their life cycle, they resemble amoebas

    in the other stage, they form moldlike clumps that produce spores


Cellular Slime Molds

    phylum Acrasiomycota

    Spend most of their lives as free-living cells resembling soil amoebas

    When food supply is gone, produce spores that can survive harsh conditions

    Reproductive steps:

1.      send out chemical signals to attract other cells of the same species

2.      thousands of cells aggregate into a large sluglike colony that functions as a single organism

3.      produces a fruiting body, slender reproductive structure that produces spores

4.      spores are scattered

5.      each spore gives rise to a single amoeba-like cell starting the cycle all over again


Acellular Slime Molds

    phylum Myxomycota

    Begin their life cycle as an amoeba-like cell

    When they aggregate, cells fuse to produce structures with many nuclei or plasmodia.

    Can grow as large as several meters in diameter

    Sporangia (small-fruiting bodies) spring up from the plasmodium

    Haploid spores scatter and germinate forming amoeba-like cells

    Cells fuse into a sexual union to produce a diploid zygote and the cycle is repeated


Water Molds

    Resembles white fuzz growing on the surface of dead fish in the water

    phylum Oomycota

    thrive on dead and decaying organic matter in the water

    some are plant parasites on land

    NOT true fungi

       Cell walls made of cellulose and produce motile spores

    Reproduce both sexually and asexually

       Asexual reproduction involves hyphae (thin filaments) which develop into zoosporangia (spore cases).  Flagellated spores swim away in search of food.  Spores develop into hyphae when they find food and grow into a new organism

       Sexual reproduction takes place in specialized structures that are formed by hyphae.  Antheridium produces male nuclei and oogonium produces female nuclei.  Fertilization takes place and spores form a new organism.


Ecology of Funguslike Protists

    Important recycles of organic material

    Help things rot

    dark, rich topsoil results from their decomposition








    land-dwelling molds cause mildews and blights of grapes, tomatoes and potatoes

    protist Phytophthora infestans, an oomycete produces airborne spores that destroy all parts of the potato

    In 1846, nearly the entire potato crop was lost in Ireland, leading to mass starvation.

    At least 1 million people died between 1845 and 1851 causing more than 1 million people to emigrate from Ireland.