7.35
Diversity of Protists II
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Q1: What are alveoli and what role do they play in alveolate protists?
Alveoli are cytoplasmic sacs located beneath the cell membrane of alveolate protists. While their exact function remains uncertain, they may help regulate water balance by controlling how much water enters and leaves the cell. In dinoflagellates, these structures may serve as armor plates, providing structural protection.
Q2: How do ciliates like Paramecium use their cilia for feeding?
Paramecium uses cilia to sweep bacteria and particles into a funnel-shaped oral groove. The material is transported to the cell mouth, or gullet, where it is enclosed in a vacuole through phagocytosis. Digestive enzymes then break down the contents to release nutrients for the cell.
Q3: What is unique about the nuclear organization in ciliates?
Ciliates possess two distinct types of nuclei: the macronucleus and micronucleus. The macronucleus manages essential cellular functions like growth and feeding, while the micronucleus is involved in sexual reproduction. Paramecium's macronuclear genome contains approximately 40,000 genes, nearly twice as many as humans.
Q4: How do dinoflagellates move and what causes their characteristic spinning motion?
Dinoflagellates move using two flagella of different lengths positioned at different angles. The movement of these flagella causes dinoflagellates to spin, which is reflected in their name derived from the Greek word for whirling. This spinning motion allows them to navigate through marine and freshwater environments.
Q5: What are sporozoites and how do apicomplexans use them?
Sporozoites are specialized structures produced by apicomplexans that aid in host infection. The name apicomplexan comes from a unique organelle complex at one end of the sporozoite that helps the parasite invade host cells. This complex is essential for the parasite's ability to establish infection in vertebrate and invertebrate hosts.
Q6: What are apicoplasts and what biosynthetic functions do they perform?
Apicoplasts are degenerate chloroplasts found in apicomplexans that no longer perform photosynthesis. They contribute to fatty acid, isoprenoid, and heme biosynthesis within the apicomplexan cell. These organelles are believed to have originated from red algae engulfed during a secondary endosymbiotic event.
Q7: Why are some dinoflagellates harmful to humans and marine ecosystems?
Certain dinoflagellates like Gonyaulax form dense blooms called red tides that produce neurotoxins. When shellfish accumulate these toxins, humans consuming them develop paralytic shellfish poisoning, causing numbness, dizziness, and potentially respiratory failure. Other species like Pfiesteria release toxic spores that kill fish and cause skin rashes in exposed humans.