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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.
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Unicellular protists carry out the same functions as multicellular organisms by using __ instead of multicellular organs.
subcellular organelles
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Compared to other eukaryotes, protists are nutritionally __.
diverse: meaning they can be photoautotrophs, heterotrophs, or mixotrophs (combination of the 2)
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How do protists reproduce?
highly varied: some sexually, some asexually
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What gave rise to enormous diversity of protists that exist today?
- 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
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DNA of plastid genes in red and green algae closely resemble the DNA of
cyanobacteria
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During eukaryotic evolution, red and green algae underwent __.
secondary endosymbiosis: They were ingested in the food vacuoles of heterotrophic eukaryotes and became endosymbionts themselves.
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Excavata
- include diplomonads, parabasalids, and euglenozoans
- Molecular data indicate they are monophyletic. (only a hypothesis)
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Diplomonads and Parasabalids both
- lack plastids
- have modified/reduced mitochondria
- found in anaerobic environments
- Many are parasites
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The modified mitochondria in Diplomonads are called __ and differ from regular mitochondria, because __.
mitosomes; They lack functional electron transport from carbs and other organic molecules. Instead, they get energy from anaerobic chemical pathways.
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structure of Diplomonads
- 2 equal-sized nuclei
- multiple flagella
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Giardia intestinalis (lamblia) is
a diplomonad (parasite) which inhabits the intestines of mammals
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The modified mitochondria in Parabasalids are called __ and they generate energy by __.
hydrogenosomes; releasing hydrogen gas as a byproduct (anaerobically)
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Trichomonas vaginalis is
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
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Euglenozoans belong to a diverse clade that includes
predatory heterotrophs, photosynthetic autotrophs, and parasites
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The main morphological feature that distinguishes euglenozoans is
the presence of a rod with either a spiral or crystalline structure inside each of their flagella
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Kinetoplastids
- 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
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Trypanosomes are
a genus of kinetoplastids (Euglenozoan) which infect humans and cause sleeping sickness, also causes Chagas' disease
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Euglenid
- a group of Euglenozoans
- has a pocket at one end from which 1 or 2 flagella emerge
- mixotrophs
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