Chapter20 Section05 edit PROTISTS MODIFIED.ppt [Mode de ... · Title: Microsoft PowerPoint - Chapter20_Section05_edit PROTISTS MODIFIED.ppt [Mode de compatibilité] Author: Ari Created

Biology

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Copyright Pearson Prentice Hall

20–5 Funguslike Protists

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Similarities and differences between funguslike

• Like fungi, funguslike protists are heterotrophs that

Similarities and differences between funguslikeprotists and fungi

g , g p pabsorb nutrients from dead or decaying organic matter. No photosynthesis.

• Unlike most true fungi, funguslike protists contain centrioles. They also lack the chitin cell walls of true yfungi.• Grow in damp, nutrient rich environments

Funguslike protist

Fungus

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protist


Two phyla of Fungulike Protists

Slime Molds

Water Molds

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20–5 Funguslike Protists Slime Molds

Slime molds

Defining characteristics of the slime molds• Slime molds are funguslike protists that play key roles• Slime molds are funguslike protists that play key roles in recycling organic material.

• At one stage of their life cycle slime molds look just• At one stage of their life cycle, slime molds look just like amoebas.

• At other stages they form moldlike clumps thatAt other stages, they form moldlike clumps that produce spores, almost like fungi.

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Video Mold Time-lapse (3min):

https://www.youtube.com/watch?v=GY_uMH8Xpy08Xpy0

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Two groups of slime molds are recognized:

• Cellular slime molds whose individual cells remain• Cellular slime molds, whose individual cells remain separated by cell membranes, 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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Cellular Slime Molds

Most cellular slime molds live as free living cells that are• 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• In nutrient-rich soils, these amoeboid cells reproduce sexually and produce diploid zygotes.

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Life Cycle of a Cellular Slime MoldLife Cycle of a Cellular Slime Mold

Fruiting body Emerging Solitary cellbody Spores Emerging

amoebas Aggregatedamoebas

Solitary cell

ZygoteZygote

Fruiting body

Migrating colony

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When food is scarce, the cells produce spores.

They emit chemicals to attract cells of the sameThey emit chemicals to attract cells of the same species.

C fCells gather into a colony that functions like one organism.

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• The colony moves slightly, then stops to produce a fruiting body, a slender reproductive structure g y, pthat produces spores.

• Then the spores are scattered from the fruitingThen the spores are scattered from the fruiting body.

E h d ll t ti th l• Each spore produces one cell, starting the cycle again.

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Video of cellular slime mold aggregating and forming fruiting bodies:g g

// / ? S C Chttps://www.youtube.com/watch?v=ShlCwqlCA4Y

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Acellular Slime Molds

A ll l li ld b i b lik llAcellular slime molds begin as amoeba-like cells.

When they aggregate, their cells fuse to produce structures with many nuclei known as plasmodium.

Eventually, the fruiting body called sporangium grows up from the plasmodium.

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Life Cycle of an Acellular Slime Mold

G i ti

Fertilization

Spores Germinating

Maturesporangium Young

sporangium MFeeding

l di

Zygote

sporangium Matureplasmodium

plasmodium

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Fruiting bodies or sporangia arise from theFruiting bodies, or sporangia, arise from the plasmodium (no link with the malaria!). The sporangia produce haploid spores by meiosisThe sporangia produce haploid spores by meiosis.

MatureY

Zygote

sporangium Youngsporangium

Matureplasmodium

Feedingplasmodium

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Spores scatter and germinate into flagellated cellsSpores scatter and germinate into flagellated cells. Cells fuse to produce diploid zygotes.

Spores Germinating

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20–5 Funguslike Protists Water Molds

Water Molds (Oomycetes)( y )Defining characteristics of the water molds

• Oomycetes or water molds thrive on dead or decaying organic matter in water. Some water molds

l t it l dare plant parasites on land.

The name Oomycete means “egg fungi” and refer to the large egg shaped female gamete oogoniumthe large egg shaped female gamete oogonium

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Water molds produce thin filaments known as hyphae. yp

Water molds have cell walls made of cellulose and produce motile spores two traits that fungi do notproduce motile spores, two traits that fungi do not have.

Water molds reproduce both sexually and asexuallyWater molds reproduce both sexually and asexually.

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FERTILIZATIONLife Cycle of a Water Mold

MEIOSISSEXUAL

REPRODUCTIONMEIOSIS REPRODUCTION

ASEXUAL REPRODUCTION

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20–5 Funguslike Protists Water molds

In asexual reproduction, portions of the hyphae develop into zoosporangia, which are spore cases.

FlagellatedSpores (N)

p p g , p

HyphaMycelium

(2N)

Spores (N)

Z i

Hypha

G i tiZoosporangium Germinationand mitosis

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Each produces flagellated spores that swim in search of food.

FlagellatedSpores (N) Hypha

Mycelium (2N)

p ( )

Zoosporangium

Hypha


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When they find food, the spores develop into hyphae, which then grow into new organisms.

FlagellatedSpores (N)

g g

HyphaMycelium

(2N)

Spores (N)

Zoosporangium

Hypha


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Sexual reproduction occurs in specialized structures formed by the hyphae.

Antheridium Egg cells (N)

Z t

FERTILIZATION

y yp

O i

Zygotes(2N)

MEIOSIS

Flagellated spores (N)Mycelium

Oogonium Male nuclei (N)

Fertilization

Zoosporangium

p ( )(2N)

SEXUAL

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SEXUAL REPRODUCTION


The antheridium produces male nuclei.


Z t

FERTILIZATION

O i

Zygotes(2N)

MEIOSIS



Fertilization

p ( )(2N)

Zoosporangium

SEXUAL

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SEXUAL REPRODUCTION


The oogonium produces female nuclei.


Z t

FERTILIZATION

O i

Zygotes(2N)

MEIOSIS



Fertilization

p ( )(2N)

Zoosporangium

SEXUAL

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SEXUAL REPRODUCTION


Fertilization occurs within the oogonium, and the spores that form develop into new organisms.


Z t

p p gFERTILIZATION

O i

Zygotes(2N)

MEIOSIS



Fertilization

p ( )(2N)

Zoosporangium

SEXUAL

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SEXUAL REPRODUCTION


Video Discharge of water mold zoospores (36sec)

https://www.youtube.com/watch?v=gDT5Pg3_nsM

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20–5 Funguslike Protists Ecology of Funguslike Protists

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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20–5 Funguslike Protists Ecology of Funguslike Protists

Some funguslike protists can harm living things.

Land dwelling water molds cause a number of plantLand-dwelling water molds cause a number of plant diseases, including mildews and blights.

f GA water mold was responsible for the Great Potato Famine in the 1800s, causing the potato blight

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Chapter20 Section05 edit PROTISTS MODIFIED.ppt [Mode de ... · Title: Microsoft PowerPoint - Chapter20_Section05_edit PROTISTS MODIFIED.ppt [Mode de compatibilité] Author: Ari Created