Module 12: eukaryotes -protists

Endosymbiotic Theory

The theory that eukaryotic cells evolved from symbiotic relationships between primitive eukaryotes and prokaryotic organisms.

Evidence for Endosymbiotic Theory

Includes double membranes in mitochondria and chloroplasts, own circular DNA, 70S ribosomes, binary fission reproduction, and genetic similarities to alpha-proteobacteria and cyanobacteria.

Distinguishing Features of Protists

Eukaryotic, mostly unicellular organisms that can be autotrophic, heterotrophic, or mixotrophic, and reproduce asexually or sexually.

Protozoans

Animal-like protists that are heterotrophic and mostly unicellular, including examples like Amoeba, Paramecium, Giardia, and Plasmodium.

Mechanisms of Motility

Methods used by protists to move, including flagella, cilia, pseudopodia, and gliding.

Trophozoite

The active, feeding, and motile stage of a protozoan.

Cyst

The dormant, resistant stage of a protozoan for survival and transmission.

Archaezoans

Primitive eukaryotes that lack mitochondria and are often anaerobic, exemplified by Giardia lamblia and Trichomonas vaginalis.

Euglenozoans

Flagellated protists with a crystalline rod in their flagella, including Euglena and Trypanosoma.

Amoebozoans

Protists that move using lobe-shaped pseudopodia, with examples like Amoeba proteus and Entamoeba histolytica.

Apicomplexans

Non-motile, obligate intracellular parasites with an apical complex, such as Plasmodium and Toxoplasma gondii.

Giardia lamblia

Causes Giardiasis, a diarrheal illness.

Trichomonas vaginalis

Causes Trichomoniasis, a sexually transmitted disease (STD).

Trypanosoma

Causes Sleeping sickness and Chagas disease.

Entamoeba histolytica

Causes Amoebic dysentery.

Plasmodium

Causes Malaria.

Flagyl (Metronidazole)

An antiprotozoal drug activated in anaerobic cells, forming free radicals that damage DNA.

Algae

Photosynthetic protists that can be unicellular, colonial, or multicellular.

Red Tide

Harmful algal bloom usually caused by dinoflagellates producing toxins.

Diatoms

Unicellular algae with silica cell walls that are major producers in aquatic ecosystems.

Significance of Diatoms

Contribute to global oxygen production and are used in forensics, filtration, abrasives, and as bioindicators.