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 Blue-green 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• 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

• 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”• 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

• 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 organicmaterial

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

Fucus“Rockweeds”Sporic meiosis

Xsec of blade

Red Algae: Phylum Rhodophyta

• 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