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Transcript
PROTISTS- Chapter 28 “More about what they are not… than what they are” CHARACTERISTICS EUKARYOTES that AREN’T animals, plants, or fungi Primarily unicellular (Paramecium, Euglena); Some colonial (Volvox); some multicellular (Seaweed) Cilia or flagella at some time in life cycle Kingdom is POLYPHYLETIC (from two or more ancestral forms) Taxonomists are attempting to create monophyletic groups using nucleic acid sequencing, cell structure THREE CATEGORIES ANIMAL-LIKE (protozoa): ingestive heterotrophs EX: amoeba, paramecium, stentor FUNGUS-LIKE absorptive heterotrophs PLANT-LIKE (algae): photosynthetic autotrophs Have chlorophyll a and accessory pigments (carotene, xanthophylls) EX: Euglena, algae, dinoflagellates, diatoms The full spectrum of modes of life unicellular to multicellular autotrophic to heterotrophic asexual to sexual reproduction pathogenic to beneficial sessile to mobile ORIGIN OF EUKARYOTES (ENDOSYMBIOTIC THEORY) Increasing multicellularity found in prokaryotes Allows for division of labor, specialization of functions, and compartmentalization. Endosymbiotic hypothesis (serial endosymbiosis) Explains origin of mitochondria and chloroplasts. Proposed by Lynn Margulis Heterotrophic and photosynthetic prokaryotes become endosymbionts. EVIDENCE: Bacteria & mitochondria/chloroplasts are similar size Inner membrane transport proteins, enzymes, lipids similar Divide by “binary fission” Circular DNA without histones Have own transcription/translation machinery HOW PROTISTS MOVE Flagella EX: Euglena Cilia EX: Paramecium BENEFICIAL Constituents of plankton (passive drifters in water) phytoplankton – (algae + diatoms) produce ~ 90% of atmospheric oxygen zooplankton -key role in aquatic food chains Symbiosis- LICHENS: (fungi + algae) make soil from rock Pseudopodia EX: amoeba HARMFUL- Pathogens Plasmodium- malaria Potato blight Trypanosomes- sleeping sickness Giardia-diarrhea