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.