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Diverse Kingdom Protista: Features & Classes

Explore the vast realm of Kingdom Protista, encompassing simple eukaryotes, diverse modes of nutrition, reproduction, and interactions with various organisms. Learn about major groups, locomotion methods, and habitats, including symbiotic relationships. Delve into the evolution of eukaryotes through the endosymbiont theory and classification methods. Discover distinctive classes like Zooflagellates, Alveolates, and Heterokonts with intriguing characteristics and ecological significance.

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Diverse Kingdom Protista: Features & Classes

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  1. Chapter 24 Protists

  2. Kingdom Protista • “Simple” eukaryotes • Mostly unicellular • Some form colonies • Some are coenocytic • Multiple nuclei in one mass of cytoplasm • A few are multicellular

  3. Most protists live in aquatic environments • Sixty major groups of protists • Important in the biosphere • Food for other organisms • Photosynthetic protists supply oxygen

  4. Locomotion • Pseudopodia • Flagella • Cilia • A few are nonmotile • Modes of nutrition • Autotrophs • Heterotrophs

  5. Chlamydomonas

  6. Interactions with other organisms • Free-living • Mutualism • Commensalism • Parasitism • Habitats • Most live in the ocean or freshwater ponds, lakes, and streams • Parasites live in host’s bodily fluids

  7. Modes of reproduction • Many protists reproduce both sexually and asexually • Syngamy (union of gametes) • Some protists are solely asexual

  8. Endosymbiont theory • Certain organelles arose from symbiosis with prokaryotes • Mitochondria arose from aerobic eubacteria • Chloroplasts arose from cyanobacteria

  9. Primary and secondary endosymbiosis

  10. Classifying eukaryotes • Ultrastructure • Fine details of cell structure • Molecular data • Ribosomal RNA • Nuclear genes • The protist kingdom is probably paraphyletic

  11. Eight monophyletic groups of eukaryotes

  12. Zooflagellates • Mostly unicellular heterotrophs • Move using flagella • Now separated into several monophyletic groups • Excavates • Discicristates

  13. Excavates live in oxygen-free environments • Diplomonads • No mitochondria • No Golgi complex • One or two nuclei • Up to eight flagella • Giardia is a parasite

  14. Giardia

  15. Discicristates have disc-shaped mitochondrial cristae • Euglenoids • About 1/3 are photosynthetic • Inhabit freshwater ponds and puddles • Trypanosoma causes African sleeping sickness

  16. Euglena gracilis

  17. Alveolates have flattened vesicles under the plasma membrane • Ciliates • Move by hairlike cilia • Micronuclei for sexual reproduction • Macronuclei control metabolism • Reproduce sexually by conjugation

  18. Paramecium, a ciliate

  19. Alveolates • Dinoflagellates • Mostly unicellular with two flagella • Mostly photosynthetic • Apicomplexans • Parasitic • Spore-forming • Plasmodium causes malaria

  20. Dinoflagellates

  21. Heterokonts are motile with two different kind of flagella • Water molds • Mycelium absorbs organic material • Reproduce asexually with biflagellate zoospores • Reproduce sexually with oospores • Phytophthora causes plant diseases

  22. Mycelium around a dead insect Saprolegnia

  23. Heterokonts • Diatoms • Mostly unicellular with shells containing silica • Some diatoms are part of plankton • Golden algae • Mostly unicellular, biflagellate algae • Both freshwater and marine

  24. Diatoms

  25. Heterokonts • Brown algae • Multicellular seaweed • Ecologically important in cooler ocean waters • Kelps have leaflike blades, stemlike stipes, anchoring holdfasts, gas-filled bladders

  26. Brown algae

  27. Cercozoa are amoeboid cells that often have hard outer shells, called tests, through which cytoplasmic projections extend

  28. Cercozoa • Foraminferans • Many-chambered tests with pores • Cytoplasmic extensions to move and obtain food • Actinopods • Mostly marine plankton • Axopods to obtain food

  29. An actinipod

  30. Plants have chloroplasts bounded by inner and outer membranes • Land plants, red algae, and green algae are monophyletic • Red algae and green algae are in kingdom Protista

  31. Red algae are mostly multicellular seaweeds • Ecologically important in warm tropical waters • Red algae with calcium carbonate in their cell walls are important for reef building

  32. Red algae

  33. Green algae are diverse in size, structural complexity, and reproduction • May be the ancestors of land plants • Multicellular forms do not have cells differentiated into tissues, unlike plants

  34. Green algae

  35. Amoebas move and obtain food using cytoplasmic extensions called pseudopodia • Capture and engulf food by surrounding it and forming a vacuole around it • Entamoeba histolytica causes amoebic dysentery

  36. Plasmoidal slime mold • Feeding stage is a multinucleate plasmodium that extends up to one foot in diameter • In the reproductive stage, stalks called sporangia produce haploid spores

  37. Plasmoidal slime mold

  38. Cellular slime molds • Feeding stage is individual amoeboid cells • During moisture or food shortage, they aggregate into a migrating pseudoplasmodium • Forms stalked fruiting body containing spores

  39. Cellular slime mold

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