PROTISTS Protists Protists Unicellular eukaryotic organisms Over 115

PROTISTS

Protists • Protists: Unicellular eukaryotic organisms. • Over 115, 000 species • Eukaryotic cells - contain membrane-bound organelles (particularly mitichondria & chloroplasts) • Protists & eukaryotes probably evolved from a large eukaryotic cell ingesting a photosynthetic and oxygen metabolizing bacteria – Known as endosymbiotic theory • Two major classes of protists – Animal-like protists – Plant-like protists

Animal-like Protists • Phylum Ciliophora (Cilia bearing protists) – – Aka "ciliates" Have cilia (short hairlike structures) on their plasma membranes – Cilia rapidly beat and provide propulsion for the protist. – Over 7000 species in this phylum. – Example is paramecium.

Paramecium • Large organisms ~305 micrometers long • Important features: • Have 2 nuclei • Macronucleus (large) • Micronucleus (smaller) • Feed by forcing H 2 O into Gullet forming food vacuoles • Excrete wastes through anal pore • Excrete excess water through use of contractile vacuoles • Move by coordinated movement of hair-like cilia.

More Paramecium

Phylum Sporozoa • Usually parasitic in nature • Example is Plasmodia which causes malaria. – One of the most deadly diseases to man – Malaria is transmitted by the Anopheles mosquito.

Lifecycle of Plasmodia

Phylum Sarcodina Protists with false feet • Use extensions of cytoplasm to move and feed. • Extensions are called pseudopods (false feet) – Movement is by extending pseudopod, then the remainder of cytoplasm flows into extension. – Feeding is done by extending 2 pseudopods around object and engulfing object, forming a food vacuole • Examples are amoebas (amebas)

Amoebas

More amoebas

Plant-like Protists • 5 phyla of plant-like protists • Are usually photosynthetic, and also heterotrophic. • All are unicellular, most are motile • Example: Phylum Euglenophyta

Phylum Euglenophyta • Example is euglena. • Has a flagellum, is motile • Is both heterotrophic & autotrophic • Contains chloroplasts & is photosynthetic. • Can become heterotrophic in lowlight conditions

Euglena

Dinoflagellates • Have 2 flagella for motility • Often have a cellulose covering

Diatoms • Most abundant form of marine algae. • Form elaborate silicon (glass) shells to protect themselves • Shell is porous to allow materials in/out of the cell.

Multicellular / Other Algae • Are not generally true multicellular organisms, but rather "colonies" • Show beginnings of specialized functions / tissues • 3 types – Green algae – Red Algae – Brown algae

Green algae (Chlorophyta) • Contain chlorophyl a & b • Most frequently found in fresh water • Often colonial Volvox: a green colonial algae

Red Algae (Rhodophyta) • Red Algae (Rhodophyta) – Found in salt/brackish water – Have additional pigments which give them a reddish color. – In uncontrolled blooms, these organisms can cause serious ecological damage Red algeal bloom

Brown Algae (Rhodophyta) • Brown Algae (Rhodophyta) – Most Plant-like of all algae. – Include kelps – Can grow to huge sizes (100') – Most primitive plant like organism to show alternation of generations. Giant Kelp Forest

Fungus like Protists: • Fungus like Protists: – Act as decomposers – Often have a slimy appearance/texture, hence their name. – 3 types: • Plasmodial slime molds • Cellular slime molds • Water molds

Plasmodial Slime Molds • Plasmodial Slime Molds – Can grow very large, however, is still a single cell (with many nuclei) – Feeding stage is called a plasmodium. – Forms fruiting bodies under stress.

Cellular Slime Molds: • Exists a majority of its life cycle as an amoeba • In times of stress these amoebas unite to form a Pseudoplasmodium, which crawls to another location (slug form), and forms a fruiting body

Water molds: molds • Water molds: – Completely aquatic – Often decomposers – Sometimes parasitic Water mold attacking a fish