Unformatted text preview: Chapter 22 Chapter 22
“Protists” – The Simplest Eukaryotes Protistans are Unlike Protistans are Unlike Prokaryotes • Eukaryotic: Have a nucleus and • • • • • •
organelles Usually unicellular Have proteins associated with DNA The DNA is linear in chromosomes, not circular like prokaryotes Use microtubules in a cytoskeleton, spindle apparatus,cilia and flagella May contain chloroplasts May divide by mitosis and meiosis Difficult to Classify Difficult to Classify
• Historically a catchall kingdom • Differ enormously from one another in morphology and lifestyles • Molecular and biochemical comparisons are clarifying the evolutionary picture • Protistans do not all stem from a common ancestor Impacts, Issues: Tiny Critters, Impacts, Issues: Big Impacts • • • • Protists – structurally the simplest of all eukaryotes Foraminiferans and coccolithophores have shells or plates hardened with calcium carbonate Dover, England’s white chalk...
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