Protista: Algae and
Heterotrophic
Protist
Protista
• diverse group of organisms, comprising
those eukaryotes that are not animals,
fungi, or plants. They are usually treated
as the kingdom Protista
Algae
• photosynthetic organisms that occur in
most habitats.
• vary from small, single-celled forms to
complex multicellular forms- giant kelp 65
meters in length.
Algae
• regarded as simple plants, they actually
span more than one domain, including
both Eukaryota and Bacteria (see Bluegreen algae), as well as more than one
kingdom, including plants and protists, the
latter being traditionally considered more
animal-like (see Protozoa).
• All lack leaves, roots, flowers, seeds and
other organ structures that characterize
higher plants (vascular plants).
Algae
• All algae have photosynthetic machinery
ultimately derived from the cyanobacteria,
and so produce oxygen as a byproduct of
photosynthesis
• algae produce about 73 to 87 percent of
the net global production of oxygen
• far more common in moist, tropical regions
than dry ones, because algae lack
vascular tissues and other adaptations to
live on land.
• Algae can endure dryness and other
conditions in symbiosis with a fungus as
lichen.
Role in Aquatic Ecology
• Microscopic forms that live suspended in
the water column — called phytoplankton
— provide the food base for most marine
food chains.
Ecology of algae
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Play a role comparable to the role played by plants in the far young
terrestrial world.
Dominant in freshwater habitats
Ponds
Streams
Lakes
Rocky shores
• Seaweeds
• Members of red, brown and
green algae
• At low tides can see distinct
layers that can withstand
large fluctuations of
humidity, temperature,
salinity and light
Offshore
• Beyond the zone of waves massive brown
kelps form forest
• Provide shelter for diverse fish and
invertebrate animals
Phytoplankton
• Plankton- minute photosynthetic cells
along with tiny animals
• Phytoplankton- photosynthetic algae and
cyanobacteria
• Phytoplankton is the beginning of the food
chain for heterotrophic organisms that live
in oceans of bodies of freshwater
Protista: Algae and Heterotrophic
Protists
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Dinoflagellates : Phylum Dinophyta
Euglenoids: Phylum Euglenophyta
Cryptomonads: Phylum Cryptophyta
Haptophytes: Phylum Haptophyta
The Heterokonts- oomycetes, diatoms, pyhaeophyta
Red Algae: Phylum Rhodophyta
Green Algae: Phylum Chlorophyta
The Slime Molds
Marine Phytoplankton
• Dinoflagellates- Phylum
Dinophyta
• Euglenoids: phylum
• Haptophytes: phylum
• Heterokonts- Oomycetes,
Diatoms, Phaeophyta
Most important eukaryotic
members of the marine
phytoplanton and therefore
essential to the support of marine
animal life
Algae and “The Carbon Cycle”
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Algae are able to transform carbon dioxide into carbohydrates or into
calcium carbonate
Today phytoplankton absorb about One-half of all the Carbon dioxide that
results from human activities
White cliffs of Dover- calcium carbon deposits “CO2 drawdown” effect
Dinoflagellates: Phylum Dinophyta
• Molecular systematic data- Related to ciliated
protozoa such as Paramecium and Vorticella
• Unicellular biflagellates
• Marine and freshwater
• Some dinoflagellates are nonmotile
• Reproduction- longitudinal cell division
Dinoflagellates
• About half lack a photosynthetic
mechanism
• Ingest solid food particles (tubular process
peduncle suction organic material)
• Or absorb dissolved organic compounds
• Many photosynthetic dinoflagellates can
feed in these ways• Mixotrophy- the ability to utilize both
organic and inorganic carbon sources.
Symbiotic forms
• Zooxanthellae- responsible for the
photosynthetic productivity that makes
possible the growth of coral reefs in
tropical waters
Dinoflagellates produce toxic or
bioluminescent compounds
• Toxic glycoside released by activated
dinoflagellate cysts
• Paralyze the respiratory tract,
dinoflagellates feed on fish then return to
cyst stage
Euglenoids: Phylum Euglenophyta
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Earliest euglenoids were phagocytes
Mostly Freshwater
Contain chloroplast
Studies suggest that euglenoids were
derived from endosymbiotic green algae
• 2/3 are colorless heterotrophs that rely
upon particle feeding or absorption
• Euglena
Euglena
• Unicellular
• Lacks cell wall or
rigid structure
covering plasma
membrane
• Beneath plasma
membrane pellicle
• Swimming Euglena
have a single long
external flagellum
Eyespot
Euglena
Crytomonads; Phylum Crytophyta
Haptophytes : Phylum Haptophyta
• Mostly Marine phytoplankton
• Few freshwater and terrestrial forms are
known
• Unicellular flagellates, colonial flagellates,
colonial flagellates and non-motile single
cells and colonies
• Haptonema- threadlike structure that
extends from the cell and can help catch
prey, and sensory
Phylum Haptophyta
• Most are photosynthetic
• Marine haptophytes
serve both as producers
and even though most
are autotrophic as
consumers (each
cyanobacteria)
• Major part in the carbon
cycle
Characteristics of Haptophyte
algae continue
• Presence of small flat scales on the outer
surface of the cell
Coccoliths
Calcified organic
material
The Heterokonts
“different flagella”
• Oomycetes; Phylum oomycota
• Diatoms: Phylum Bacillariophyta
• Brown algae: Phylum Phaeophyta
Oomycetes; Phylum Oomycota
“Fungus-like”
• Heterotrophic
• The water molds
– Saprolegnia can reproduce sexually
(heterothallic) and asexually (homothallic)
• Terrestrial Oomycetes
Bacillariophyta(Diatoms) and
Phaeophyta
• Autotrophic
• Have chlorophyll and carry on
photosynthesis (algae)
• Bacillariophyta: The Diatoms
• Phaeophyta: The Brown Algae
Bacillariophyta: The Diatoms
“algae that live in glass houses”
• Unicellular or colonial organisms
• Fresh and marine waters
• Two types of diatoms based on structure
– Pennate
– Centric
Phaeophyta: The Brown Algae
• Mostly Marine form
• Abundant in cold
ocean waters
• Kelps- Laminaria,
Postelsia,
Macrocystis,
Nereosystis
Sieve tubes
• Located within the phoelm
• Transport of carbohydrates in the plant
Xsec of
blade
Fucus
“Rockweeds”
Sporic meiosis
Red Algae: Phylum Rhodophyta
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Mostly marine form
Warm sease
Include “sea mosses”
Usually less than 10 cm long
Green Algae: Phylum Chlorophyta
• Class chlorophyceae
• Class Ulvophyceae, The Ulvophytes
– Mainly marine
The Slime Molds
• Phylum Myxomycota
– Sporangium of Arcyria nutans
– Sporangia of Stemonitis splendens
– Plamodiocarp of Hemitrichia serpula
– Aethalia of Lycogala