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Biology
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20–5 Funguslike Protists
Photo Credit: ©L.West/Photo Researchers, Inc.
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What are the similarities and differences between funguslike protists and fungi?
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Funguslike protists are heterotrophs that absorb nutrients from dead or decaying organic matter.
Unlike most true fungi, funguslike protists contain centrioles. They also lack the chitin cell walls of true fungi.
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Slime Molds
Slime Molds
What are the defining characteristics of the slime molds?
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Slime Molds
Slime molds are funguslike protists that play key roles in recycling organic material.
At one stage of their life cycle, slime molds look just like amoebas.
At other stages, they form moldlike clumps that produce spores, almost like fungi.
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Slime Molds
Two groups of slime molds are recognized:
Cellular slime molds, whose individual cells remain separated during every phase of the mold's life cycle.
Acellular slime molds, which pass through a stage in which its cells fuse to form large cells with many nuclei.
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Slime Molds
Cellular Slime Molds 
Most cellular slime molds live as free-living cells that are not easily distinguishable from soil amoebas.
In nutrient-rich soils, these amoeboid cells reproduce sexually and produce diploid zygotes.
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Slime Molds
Life Cycle of a Cellular Slime Mold
Fruiting body
Emerging
amoebas
Solitary cell
Spores
Aggregated
amoebas
Zygote
Fruiting body
Cellular slime molds reproduce asexually and sexually.
Migrating colony
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Slime Molds
When food is scarce, the cells produce spores.
They emit chemicals to attract cells of the same species.
Cells gather into a colony that functions like one organism.
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Slime Molds
The colony moves slightly, then stops to produce a fruiting body, a slender reproductive structure that produces spores.
Then the spores are scattered from the fruiting body.
Each spore produces one cell, starting the cycle again.
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Slime Molds
Acellular Slime Molds 
Acellular slime molds begin as amoeba-like cells.
When they aggregate, their cells fuse to produce structures with many nuclei known as plasmodia.
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Slime Molds
Life Cycle of an Acellular Slime Mold
Fertilization
Germinating
Zygote
Spores
Mature
sporangium
Young
sporangium
Feeding
plasmodium
Mature
plasmodium
The plasmodium of an acellular slime mold is the collection of many amoeba-like organisms contained in a single cell membrane. The plasmodium will eventually produce sporangia, which in turn will undergo meiosis and produce haploid spores. Upon pairing up and fusing, these result in new diploid amoeba-like cells. 
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Slime Molds
Fruiting bodies, or sporangia, arise from the plasmodium.
The sporangia produce haploid spores by meiosis.
Zygote
Mature
sporangium
Young
sporangium
Feeding
plasmodium
Mature
plasmodium
The plasmodium of an acellular slime mold is the collection of many amoeba-like organisms contained in a single cell membrane. The plasmodium will eventually produce sporangia, which in turn will undergo meiosis and produce haploid spores. Upon pairing up and fusing, these result in new diploid amoeba-like cells. 
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Slime Molds
Spores scatter and germinate into flagellated cells.
Cells fuse to produce diploid zygotes.
The plasmodium of an acellular slime mold is the collection of many amoeba-like organisms contained in a single cell membrane. The plasmodium will eventually produce sporangia, which in turn will undergo meiosis and produce haploid spores. Upon pairing up and fusing, these result in new diploid amoeba-like cells. 
Germinating
Spores
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Water Molds
Water Molds
What are the defining characteristics of the water molds?
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Water Molds
Oomycetes, or water molds thrive on dead or decaying organic matter in water. Some water molds are plant parasites on land.
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Water Molds
Water molds produce thin filaments known as hyphae.
Water molds have cell walls made of cellulose and produce motile spores, two traits that fungi do not have.
Water molds reproduce both sexually and asexually.
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Water Molds
Life Cycle of a Water Mold
FERTILIZATION
SEXUAL REPRODUCTION
MEIOSIS
ASEXUAL REPRODUCTION
Water molds live on decaying organic matter in water. Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia. During sexual reproduction, a male nucleus fuses with a female nucleus.
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Water molds
In asexual reproduction, portions of the hyphae develop into zoosporangia, which are spore cases.
Flagellated
Spores (N)
Hypha
Mycelium
(2N)
Zoosporangium
Germination
and mitosis
Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia.
ASEXUAL REPRODUCTION
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Water Molds
Each produces flagellated spores that swim in search of food.
Flagellated
Spores (N)
Hypha
Mycelium
(2N)
Zoosporangium
Germination
and mitosis
Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia.
ASEXUAL REPRODUCTION
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Water Molds
When they find food, the spores develop into hyphae, which then grow into new organisms.
Flagellated
Spores (N)
Hypha
Mycelium
(2N)
Zoosporangium
Germination
and mitosis
Water molds reproduce both asexually and sexually. During asexual reproduction, flagellated spores are produced by the diploid (2N) mycelium. These spores grow into new mycelia.
ASEXUAL REPRODUCTION
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Water molds
Sexual reproduction occurs in specialized structures formed by the hyphae.
Egg cells (N)
Antheridium
FERTILIZATION
Zygotes
(2N)
MEIOSIS
Oogonium
Male nuclei (N)
Fertilization
Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus.
Flagellated spores (N)
Mycelium
(2N)
Zoosporangium
SEXUAL REPRODUCTION
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Water molds
The antheridium produces male nuclei.
Antheridium
Egg cells (N)
FERTILIZATION
Zygotes
(2N)
MEIOSIS
Oogonium
Male nuclei (N)
Fertilization
Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus.
Flagellated spores (N)
Mycelium
(2N)
Zoosporangium
SEXUAL REPRODUCTION
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Water molds
The oogonium produces female nuclei.
Egg cells (N)
Antheridium
FERTILIZATION
Zygotes
(2N)
MEIOSIS
Oogonium
Male nuclei (N)
Fertilization
Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus.
Flagellated spores (N)
Mycelium
(2N)
Zoosporangium
SEXUAL REPRODUCTION
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Water molds
Fertilization occurs within the oogonium, and the spores that form develop into new organisms.
Egg cells (N)
Antheridium
FERTILIZATION
Zygotes
(2N)
MEIOSIS
Oogonium
Male nuclei (N)
Fertilization
Water molds reproduce both asexually and sexually. During sexual reproduction, a male nucleus fuses with a female nucleus.
Flagellated spores (N)
Mycelium
(2N)
Zoosporangium
SEXUAL REPRODUCTION
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27. Ecology of Funguslike Protists
Slime molds and water molds recycle organic material.
After organisms die, their tissues are broken down by slime molds, water molds, and other decomposers.
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28. Ecology of Funguslike Protists
Some funguslike protists can harm living things.
Land-dwelling water molds cause a number of plant diseases, including mildews and blights.
A water mold was responsible for the Great Potato Famine in the 1800s.
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20–5
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20–5
Unlike the true fungi, funguslike protists
do not have centrioles or cell walls made of chitin.
do not have centrioles but have cell walls made of chitin.
have centrioles but lack cell walls made of chitin.
have both centrioles and cell walls made of chitin.
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20–5
The spore cases formed by water molds are called
zoosporangia.
plasmodia.
antheridia.
sporophytes.
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20–5
The acellular slime molds got their name because
they are the only organisms that do not have cells.
they do not have true nuclei.
they have multinucleate hyphae.
their cells sometimes fuse to form structures with many nuclei.
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20–5
Organisms that spend part of their life cycle as independent, unicellular amoeba-like forms and then join together as a visible, sluglike colony are
cellular slime molds.
water molds.
acellular slime molds.
plasmodia.
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20–5
The Great Potato Famine was caused by a(an)
cellular slime mold.
acellular slime mold.
water mold.
plasmodia.
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