alternation.html: 28_21LaminariaLifeCycle.jpg
Algae alternation of generations.
The multicellular, diploid sporophyte produces haploid spores by meiosis.
The spores develop into multicellular, haploid gametophytes by mitosis.
The gametophytes release gametes, which may fuse to yield diploid zygotes.
A zygote develops into a multicellular, diploid sporophyte.
amoeba.html: 28_03lAmoeba-L.jpg
An amoeba moves by extending a pseudopodium, where the
cytoplasm
switches between a liquid sol state (endoplasm) and a gel-like state (ectoplasm).
The pseudopodium can also be used to capture prey into a food vacuole.
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cellular.html: 28_25CellSlimeLifeCyc_2-L.jpg
A cellular slime mold can live as unicellular amoebae,
but can aggregate to form a multicellular pseudoplasmodium, or "slug",
in the haploid stage.
The "slug" migrates to a new location,
then forms a stalked fruiting body that releases spores which develop into new amoebae.
conjugation.html: 28_11bParamecReprod_2-L.jpg
Conjugation in Paramecium.
diatom.html: 28_16DiatomDiversity_LP.jpg
Diatoms are unicellular algae which make up a major component of phytoplankton
(drifting photosynthetic organisms).
This diverse group has a two-part, glass-like wall
of hydrated silica.
_Vid_Campbell7e/DiatomsMoving-V.swf
diatomaceous.html: 28_diatomaceous.jpg
Massive accumulations of fossilized diatom walls form sediments known as diatomaceous earth,
which is mined as a filtering and absorbing
medium
and as an abrasive control of crawling invertebrate
pests.
dino.html: 28_10Dinoflagellate.jpg
Pfiesteria shumwayae, a dinoflagellate.
A spiral flagellum lies in a groove around the cell, which is reinforced by internal plates of cellulose.
Some of these photosynthetic species can undergo explosive
growth
and cause red tides.
Their toxins can accumulate in molluscs and result in shellfish poisoning.
euglena.html: 28_07Euglena-L.jpg
Like most Euglenozoa,
the freshwater protist Euglena has a pellicle under the plasma membrane for protection,
flagella, an eyespot for directing light to the light detector that detects light, and
chloroplasts that perform photosynthesis.
Bands of protein pellicle beneath the plasma membrane provides protection.
euglenozoa.html: 28_06EuglenaFlagellus.jpg
Euglenozoan flagellum.
Most euglenozoans
have a crystalline rod inside one of their flagella. The rod lies alongside the 9 + 2 ring of microtubules found in all
eukaryotic
flagella.
eukarya.html: 28_03aEukaryotePhylo-L.jpg
Domain Eukarya can be divided into five supergroups.
Organisms in kingdom Protista are scattered among the supergroups,
and certain groups within Protista are more closely related to the other 3 eukaryote kimgdoms
than to other protists.
golden_alga.html: 28_17Dinobryon.jpg
Dinobryon, a fresh water colonial golden alga.
Golden algae, or chrysophytes, are named for their color,
which results from their carotenoid pigments.
Their flagella can trap food particles and digest them by phagocytosis,
thus they are mixotrophic: both photosynthetic and heterotrophic.
green_alga.html: 28_30Chlorophytes.jpg
Chlorophytes (Green algae).
kelp.html: 28_19KelpForest.jpg
A kelp forest.
The great kelp
beds of temperate coastal waters provide habitat and food for a variety of organisms,
including many fish species caught by humans.
Macrocystis, a kelp common along the Pacific coast of the United States,
can grow more than 60 m in a single season, the fastest linear growth recorded in any organism.
mixo.html: 28_Gymnodinium.jpg
The dinoflagellate Gymnodinium is mixotrophic: after feeding
on the golden alga Rhodomonas salina, it retains the functional chloroplasts of the prey for a few days.
paramecium.html: 28_12ParamecStructFuncA.jpg
Ciliates such as Paramecium have a large macronucleus and a small micronucleus.
They use cilia to move and feed.
Contractile vacuoles perdiodically
pump
out excess water which had entered the cell by osmosis from the hypotonic environment.
_Vid_MicroscopyU/paramecium17df40x.rm
plasmodial.html: 28_24PlasmodialLifCyc_3-L.jpg
Acellular (Plasmodial) Slime Mold.
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Physarum polycephalum forms one large cell (plasmodium) in the diploid stage with thousands of
nuclei during the diploid stage of its life cycle.
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Note: Plasmodium
is a different protozoan which causes malaria.
plasmodium.html: 28_10PlasmodLifeCycle_3-L.jpg
Plasmodium is a parasite transmitted by the Anopheles mosquito and causes malaria in humans.
After a stage in the liver, merozoites use their apex to penetrate and reproduce in red blood cells.
Eventually the host cells rupture to release gametes, causing periodic fevers and chills.
plastid.html: 28_03PlastidDiversity.jpg
Serial endosymbiosis.
Plastids (pigment-bearing organelles such as chloroplasts)
evolved from a cyanobacterium that was engulfed by a heterotrophic eukaryote
(primary endosymbiosis
). That ancestral eukaryote diversified into
red algae and
green algae,
some of which were subsequently engulfed by other eukaryotes (secondary endosymbiosis).
Some of these plastids may contain a small nucleus.
protista.html: 28_03.jpg
Protists are eukaryotes, and comprise a wide diversity of forms.
red_alga-Nori.html: 28_20EdibleSeaweed.jpg
Edible red algae.
Nori is a traditional Japanese food made from the "seaweed" Porphyra.
red_alga.html: 28_28RedAlgae.jpg
Red algae (Rhodophyta).
Red algae contain the pigment
phycoerythrin,
which masks the green of
chlorophyll.
Some, such as Bonnemaisonia hamifera, have a filamentous form,
while Dulse (Palmaria palmata) are “leafy” and
edible.
seaweed.html: 28_18Seaweeds.jpg
Brown algae (Phaeophyta).
Many brown algae are multicellular "seaweeds".
The sea palm (Postelsia) lives on rocks along the Pacific coast of north America.
The thallus (undifferentiated tissue) is composed of
trypanosoma.html: 28_06Trypanosoma-L.jpg
Trypanosoma is a parasite transmitted by the tsetse fly and causes the neurological disorder
sleeping sickness in humans.
ulva.html: 28_30Ulva.jpg
Ulva, or sea lettuce.
This edible seaweed has a multicellular
thallus differentiated into leaflike blades and a rootlike holdfast
that anchors the alga against turbulent waves and tides.
volvox.html: 28_30axVolvoxPhoto_UP.jpg
Volvox, a colonial freshwater chlorophyte.
The colony wall is composed of biflagellated cells that cannot reproduce if isolated.
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The colony also contains 16 asexual reproductive cells called gonidia
which divide to form “daughter” colonies.
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