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Protists

Protists. Chapter 25. Learning Objective 1. What features are common to the members of kingdom Protista?. Protists. Mostly unicellular eukaryotic organisms that live in aquatic environments. Sizes of Protists. Unicellular organisms microscopic Colonies loosely connected groups of cells

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Protists

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  1. Protists Chapter 25

  2. Learning Objective 1 • What features are common to the members of kingdom Protista?

  3. Protists • Mostly unicellular eukaryotic organisms that live in aquatic environments

  4. Sizes of Protists • Unicellular organisms • microscopic • Colonies • loosely connected groups of cells • Coenocytes • multinucleate masses of cytoplasm • Multicellular organisms • composed of many cells

  5. Chlamydomonas • A unicellular protist

  6. Flagella Cell wall Nucleus Chloroplast Starch granule Fig. 25-1, p. 531

  7. KEY CONCEPTS • Protists are a diverse group of eukaryotic organisms, most of which are microscopic

  8. Learning Objective 2 • Discuss in general terms the diversity inherent in the protist kingdom • means of locomotion • modes of nutrition • interactions with other organisms • habitats • modes of reproduction

  9. Locomotion • Pseudopodia • Flagella • Cilia • Some are nonmotile

  10. Nutrition • Protists obtain their nutrients autotrophically or heterotrophically

  11. Interactions • Protists are free-living or symbiotic • Symbiotic relationships range from mutualism to parasitism

  12. Habitats • Most protists live in • ocean • freshwater ponds • lakes • streams • Parasitic protists live in body fluids of hosts

  13. Reproduction • Many protists reproduce both sexually and asexually • Others reproduce only asexually

  14. KEY CONCEPTS • Protists vary in body plan (unicellular, colonial, coenocytic, multicellular), method of motility (pseudopodia, cilia, flagella), nutrition type (autotrophic, heterotrophic), and mode of reproduction (asexual, sexual)

  15. Learning Objective 3 • What is the hypothesis of serial endosymbiosis? • Explain some evidence that supports it

  16. Serial Endosymbiosis • Hypothesis: • Mitochondria and chloroplasts arose from symbiotic relationships between larger cells and smaller prokaryotes that were incorporated and lived within them

  17. Mitochondria • Probably originated from aerobic bacteria • Ribosomal RNA data suggests • ancient purple bacteria were ancestors of mitochondria

  18. Chloroplasts • Single primary endosymbiotic event • in red algae, green algae, and plants • cyanobacterium incorporated into a cell • Multiple secondary endosymbioses • in euglenoids, dinoflagellates, diatoms, golden algae, brown algae • nonfunctional chloroplasts in apicomplexans

  19. Chloroplast Evolution

  20. Mitochondrion Nucleus Eukaryotic cell with mitochondria Bacterial DNA (a) Primary endosymbiosis Cyanobacterium (ancestor of chloroplast) Fig. 25-2a, p. 532

  21. Eukaryotic cell with mitochondria Chloroplast DNA (b) Secondary endosymbiosis Chloroplast with two membranes Eukaryotic cell with mitochondria and chloroplasts (red alga) Chloroplast with three membranes Eukaryotic cell with mitochondria and chloroplasts (dinoflagellate?) Fig. 25-2b, p. 532

  22. Mitochondrion Nucleus Bacterial DNA Eukaryotic cell with mitochondria (a) Primary endosymbiosis Cyanobacterium (ancestor of chloroplast) Eukaryotic cell with mitochondria Chloroplast DNA (b) Secondary endosymbiosis Chloroplast with two membranes Eukaryotic cell with mitochondria and chloroplasts (red alga) Chloroplast with three membranes Eukaryotic cell with mitochondria and chloroplasts (dinoflagellate?) Stepped Art Fig. 25-2b, p. 532

  23. Learning Objective 4 • What kinds of data do biologists use to classify eukaryotes?

  24. Relationships Among Protists • Protist kingdom • paraphyletic group • Determined by • ultrastructure (electron microscopy) • comparative molecular data

  25. Eukaryote Phyla

  26. Zooflagellates (diplomonads) Zooflagellates (euglenoids) Apicomplexans Land plants Water molds Brown algae slime molds slime molds Green algae Animals Plasmodial Fungi Red algae Amoebas Cellular Ciliates A Ancestral eukaryote Fig. 25-3, p. 533

  27. Eukaryote Clades

  28. Plants Excavates Alveolates Cercozoa Discicristates Amoebozoa Heterokonts Opisthokonts Foraminiferans and actinopods Apicomplexans Zooflagellates, (euglenoids) Plasmodial slime molds Cellular slime molds Zooflagellates (diplomonads) Water molds Green algae Brown algae Land plants Animals Red algae Fungi Amoebas Ciliates ? Ancestral eukaryote Fig. 25-4, p. 535

  29. KEY CONCEPTS • Protists are descendants of early eukaryotes

  30. Learning Objective 5 • Why are zooflagellates no longer classified in a single phylum? • Distinguish among diplomonads, euglenoids, and choanoflagellates

  31. Zooflagellates • Mostly unicellular heterotrophs • Move by whiplike flagella • Polyphyletic • separated into several monophyletic groups

  32. Diplomonads • Diplomonads are excavates • with a deep (excavated) oral groove • Diplomonads have • one or two nuclei • no mitochondria • no Golgi complex • up to eight flagella

  33. Excavates

  34. Nucleus Flagella 50 µm Fig. 25-5b, p. 536

  35. Euglenoids • Euglenoids are discicristates • with disclike cristae in mitochondria • Euglenoids • are unicellular and flagellate • some are photosynthetic • Trypanosoma • causes African sleeping sickness

  36. Discicristates

  37. Flagellum for locomotion Eyespot Contractile vacuole Chloroplast Nucleus Paramylon body (stored food) Pellicle 25 µm Fig. 25-6a, p. 537

  38. Flagellum for locomotion Nonemergent flagellum (indistinguishable in micrograph) Eyespot Contractile vacuole Mitochondria (indistinguishable in micrograph) Chloroplast Nucleolus Nucleus Chromatin Paramylon body (stored food) Pellicle Fig. 25-6b, p. 537

  39. Red blood cells Trypanosome with undulating membrane Flagellum 25 µm Fig. 25-6c, p. 537

  40. Choanoflagellates • Choanoflagellates are opisthokonts • single posterior flagellum in flagellate cells • collar of microvilli surrounds base of flagellum • Choanoflagellates • are related to fungi and animals

  41. Choanoflagellate

  42. Flagellum Collar of microvilli Cell Lorica (protective cover) Stalk Fig. 25-25, p. 551

  43. Learning Objective 6 • Describe and compare these alveolates: • ciliates • dinoflagellates • apicomplexans

  44. Ciliates • Alveolates • move by hairlike cilia • micronuclei (for sexual reproduction) • macronuclei (for cell metabolism and growth) • undergo complex sexual reproduction (conjugation)

  45. Ciliates

  46. Cilia Food vacuoles Micronucleus Macronucleus Contractile vacuole 50 µm Fig. 25-7a, p. 538

  47. Cilia Food vacuoles Food Micronucleus Macronucleus Oral groove Contractile vacuole Anal pore Food vacuole Fig. 25-7b, p. 538

  48. Cytopharynx Macronucleus 250 µm Fig. 25-7c, p. 538

  49. Cirri Fig. 25-7d, p. 538

  50. Conjugation

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