Ch. 28: Protists

• mostly unicellular eukaryotes: simplest eukaryotes
• 0.5-2 micrometers in diameter (small as many prokaryotes)
• Some are more closely related to plants, fungi, or animals than they are to other protists.

subcellular organelles

diverse: meaning they can be photoautotrophs, heterotrophs, or mixotrophs (combination of the 2)

highly varied: some sexually, some asexually

• endosymbiosis
• First eukaryotes acquired mitochondria by engulfing an aerobic prokaryote.
• An additional endosymbiont is a photosyntetic cynobacterium that evolved into plastids.
• Plastids gave rise to 2 lineages of photosynthetic protists, or algae

cyanobacteria

secondary endosymbiosis: They were ingested in the food vacuoles of heterotrophic eukaryotes and became endosymbionts themselves.

• include diplomonads, parabasalids, and euglenozoans
• Molecular data indicate they are monophyletic. (only a hypothesis)

• lack plastids
• have modified/reduced mitochondria
• found in anaerobic environments
• Many are parasites

mitosomes; They lack functional electron transport from carbs and other organic molecules. Instead, they get energy from anaerobic chemical pathways.

• 2 equal-sized nuclei
• multiple flagella

a diplomonad (parasite) which inhabits the intestines of mammals

hydrogenosomes; releasing hydrogen gas as a byproduct (anaerobically)

a parabasalid; sexually transmitted parasite that travels along the mucus-coated lining of the human reproductive and urinary tract by moving its flagella and by undulating part of its plasma membrane

predatory heterotrophs, photosynthetic autotrophs, and parasites

the presence of a rod with either a spiral or crystalline structure inside each of their flagella

• a group of Euglenozoans
• have a single, large mitochondrion that contains a organized mass of DNA called a kinetoplast
• include species that feed on prokaryotes in freshwater, marine, and moist terrestrial ecosystems
• also species that parasitize animals, plants, and other protists

a genus of kinetoplastids (Euglenozoan) which infect humans and cause sleeping sickness, also causes Chagas' disease

• a group of Euglenozoans
• has a pocket at one end from which 1 or 2 flagella emerge
• mixotrophs