Protozoans / Protists - Key Terms

Vocabulary flashcards covering key terms related to protozoans, their nutrition, locomotion, digestion, reproduction, and major phyla and representative species.

Protozoans / Protists

Single-celled eukaryotes whose entire physiology occurs within one cell (protoplasmic level); widely distributed and often moisture-dependent.

Protoplasmic level

Level of organization where the entire physiology occurs within a single cell.

Autotrophs

Organisms that synthesize their own food (e.g., via photosynthesis); includes plant-like protists and some members of Plantae and Fungi as per notes.

Heterotrophs

Organisms that obtain organic molecules from other organisms; includes animal-like protists and many metazoans.

Phagotrophs / Holozoic feeders

Heterotrophs that feed on particulate solid food acquired through phagocytosis.

Osmotrophs / Saprozoic feeders

Heterotrophs that ingest soluble (dissolved) food through osmosis.

Cilia

Short locomotory structures made of microtubules; beat to move the organism or help in food intake; typically numerous.

Flagella

Long locomotory structures made of microtubules; fewer in number and provide movement through whip-like beating.

Pseudopodia

False feet; extensions of the cytoplasm used for locomotion and engulfing food, especially in amoebas.

Cytosome

Primitive mouth in ciliated protozoa where food is directed for ingestion.

Phagocytosis

Engulfing and intake of solid food particles by membrane invagination and vesicle formation.

Pinocytosis

Ingestion of soluble liquids via vesicles; 'drinking' of fluids at the cellular level.

Exocytosis

Process by which materials are released from the cell; often used to expel undigested material.

Binary fission

Asexual reproduction where the cell divides into two identical offspring.

Budding

Asexual reproduction where a smaller progeny cell forms on the parent and grows, then separates.

Multiple fission / Schizogony

Nucleus divides multiple times to form schizonts, which then produce many merozoites.

Sporogony

Sexual reproduction stage following gamete union; leads to formation of spores/merozoites after multiple fission.

Syngamy

Fusion of two gametes or cells to form a zygote.

Conjugation

Exchange of gametic nuclei between paired ciliates; after separation, offspring have new genetic information.

Gametogony

Sexual reproductive stage preceding sporogony; haploid gametes may fuse to form a zygote.

Phylum Sarcomastigophora

Phylum with locomotory organs (pseudopodia, flagella, or both); mostly asexual reproduction with some sexual forms; includes Mastigophora and Sarcodina.

Subphylum Mastigophora

Flagellates; about 1,500 species; freshwater and marine; reproduce by binary fission or syngamy; contains disease-causing species.

Euglena

Common free-living flagellate in freshwater; often greenish from chloroplasts; orange eye spot part of a light-sensing organelle.

Giardia lamblia

Intestinal protozoan parasite causing giardiasis; transmitted via fecal-oral route; cysts passed in feces; “smiley face” characteristic.

Trypanosoma spp.

Parasites in blood causing African sleeping sickness; transmitted by tsetse flies; also causes diseases in animals (Surra, Nagana).

Leishmania donovani

Parasite causing cutaneous leishmaniasis; transmitted by sandflies (Phlebotomus).

Subphylum Sarcodina

Pseudopodial locomotion; around 11,500 species; mostly free-living, some parasitic; reproduction by binary fission or syngamy.

Entamoeba histolytica

Parasite causing amoeboid dysentery; transmitted via contaminated water; cysts passed in feces.

Acanthamoeba keratitis

Eye infection caused by amoebae; linked to contact lens use in water; can lead to keratitis and possible blindness.

Phylum Apicomplexa

Also known as Sporozoans; obligate intracellular parasites; apical complex used to invade host cells; complex life cycle with asexual and sexual phases; no flagella and single nucleus.

Plasmodium spp. (P. malariae, P. vivax, P. falciparum)

Causative agents of malaria; transmitted by Anopheles mosquitoes; parasites of red blood cells causing fever and anemia.

Toxoplasma gondii

Common parasite; infects cats' intestinal cells; can encyst in muscles of other animals; humans can be infected via undercooked meat or vertical transmission.

Eimeria spp.

Common intestinal protozoal parasite in animals; causes coccidiosis; transmitted via infected feces or tissue.

Phylum Ciliophora

Ciliates; many free-living carnivores; some parasitic; possess two nuclei: macronucleus and micronucleus; reproduce by binary fission and conjugation.

Paramecium caudatum

Notable free-living ciliate; large and well-studied.

Balantidium coli

Large parasitic ciliate infecting humans; pigs can be carriers; causes balantidiasis.

Phylum Dinoflagellata

Dinoflagellates; major marine primary producers; photoautotrophic and heterotrophic; two flagella (equatorial & longitudinal); some produce toxins causing red tides; many are bioluminescent.

Noctiluca scintillans

Colorless dinoflagellate; voracious predator; bioluminescent; blooms can make shores glow blue.