Protists

1. Protists Chapter 18

2. What are protists? • Common features

3. Endosymbiosis/ Lynn Margulis • Theory of endosymbiosis proposes that mitochondria originated as symbiotic, aerobic bacteria. • Each mitochondrion has its own genome in a circular, closed molecule of DNA. • divide by simple fission • directed by nuclear genes

4. Theory of Endosymbiosis

5. The Protists • The kingdom Protista is the most diverse kingdom • Historically, organisms that do not fit comfortably into the other kingdoms have been placed within this kingdom. • The “junk drawer” of the classification system.

6. The Protists • All protists are eukaryotes. This is the extent of their similarities. • There have been movements in recent years to further divide the kingdom Protista into more kingdoms. This has had some success. There have been some regroupings at the phyla level.

7. General Characteristics • Mostly aerobic respirators • Mostly motile during at least some stage • Mostly chemoheterotrophs (algae excepted) • Mostly aquatic (or at least favoring moist conditions • Reproductively diverse • All are eukaryotic

8. Motility • Most protists possess a flagella, cilia, or pseudopods during at least some portion of their life histories. • Rhodophyta are an exception. This is in contrast with nearly all fungi which never possess flagella or cilia

9. Chemoheterotrophic • Most protists are chemoheterotrophs. • Exceptions include the various algae. • There are protists, the mixotrophs, that combine chemoheterotrophy with photoautotrophy using chloroplasts when light is available and absorbing nutrients when light is not available. Euglena is an example • Animals and fungi are also chemoheterotrophs

10. Aquatic • Attach to non-floating aqueous surfaces (rocks or sand on the bottom of a body of water). These are described as benthic. • Float within bodies of water. These are described as planktonic. • Inhabit the body fluids of animals or plants. These are described as non-free living as well as parasitic.

11. Aquatic Producers • Phytoplankton (planktonic algae) and the prokaryote cyanobacteria are the bases of most marine and freshwater food webs. • They account for at least half of the photosynthetic production of organic material globally.

12. Reproduction • Asexual: reproduction solely via mitosis • Sexual with no mitosis in the diploid state • Alternation of generations • Sexual protists display syngamy (two haploid cells fuse to form a diploid cell) and the life histories of many protists are further complicated by an ability to differentiate into cysts

13. The Protists • One way to artificially group the protists, or at least something to keep in mind as you study the protist kingdom, is by nutrient acquisition.

14. The Protists • Engulfers: Obtain nutrients by engulfing particles of food. These are often called the protozoa. Also called phagotrophs.

15. The Protists • Nutrient absorbers: non-fungus, non-animal eukaryotes that obtain their nutrients by absorption across their cell membrane. These are often referred to as the fungus-like protists. Also called osmotrophs.

16. The Protists • Photosynthesizers: non-plant photosynthetic eukaryotes. Also called phototrophs.

17. Aerobic Respirators • Most protists are aerobic respirators, possessing mitochondria. • Two examples are Pelomyxa palustris and Giardia lamblia.

18. Protists • Monera 3.5 billion years ago • Protists 1.5 billion years ago • Total of 9 phyla

19. Protist Classification

20. “Animal Like” • Ciliophora • Zoomastigina • Sporozoa • Sacrodina –(amebas, heliozoans,radiolarians, foraminiferas)

21. “Plant like” • Euglenophyta • Pyrrophyta • Chrysphyta • Slimemolds– Acrasiomycota, Myxomycota

22. Ciliophora • Most members have large number of cilia • About 8,000 species • Live mostly in fresh water • Use of a gullet to engulf food which is then encased in a vacuole to be digested. • Solid waste is expelled via a cyotproct.

23. Ciliophora • Reproduction is both asexual and sexual • Have two different nuclei • Micronuclei: contain normal chromosomes and function like the nuclei of other organisms • Macronuclei: DNA is divided into smaller pieces equivalent to single genes

24. Ciliophora • Asexual reproduction consists of transverse fission where the cell divides across its short axis • This type of reproduction occurs for a limited number of generations, then the cells die if sexual reproduction has not occurred.

25. Ciliophora • The macronucleus controls the cell and contains over fifty copies of the cell's genes. • The micronuclei are used in sexual reproduction where conjugation is used to increase the genetic variation of the organisms produced.

26. Paramecium

27. Paramecium

28. Zoomastigina • What does the name suggest? Characteristics? Flagella Obtain food through cell membrane Some can make gametes Some are parasitic

29. Phylum Zoomastigina • Famous Flagelate: • Trichonympha

30. Sporozoa • All are parasitic • Nonmotile • Reproduction by means • of spores

32. Plasmodium In the first stage of malaria infection, mosquitoes inject worm-like sporozoites into their human hosts as they feed on blood. When the sporozoites invade liver cells, they mature into merozoites. In the third stage, merozoites infiltrate red blood cells and mature into egg-like gametocytes. These then burst out of blood cells and are sucked out of infected individuals by feeding mosquitoes. Finally, the gametocytes mature in mosquitoes and produce new sporozoites, which the insect injects the next time it feeds.

33. Plasmodium Life Cycle

34. Sacrcodina • Protists with fake teeth • Pseudopods • Binary fission • Amebas, Heliozoans, Radiolarians, Foraminifers

35. Amoebas Draw an Amoeba and identify it’s parts page 389, figure 18-2

37. Sarcodina/ Radiolarians • Check Haeckel's Kunstformen der Natur (1904) Illustrations!!

38. Heliozoans

39. Foraminers

40. Written activity Read and answer questions on page 391 14 points, please complete sentences.

41. “Plant Like Protists” • Eugenophyta • Pyrrophyta • Chysphyta • Acrasiomycota • Myxomycota

42. Eugenophyta • Flagellates with chloroplasts

43. Euglenozoa • Some members photosynthesize, but are not classified with the algae. • Some sources have made this group a kingdom level group.

44. Euglenozoa • Euglenoids • most are freshwater • about one-third are autotrophic • pellicle lies within membrane • stigma - light sensitive organ that aids in orienting toward light • Euglena • two flagella attached to reservoir • contain numerous chloroplasts

45. Euglenozoa

46. Euglenozoa • Kinetoplastids • unique, single mitochondrion in each trypanosome • Trypanosomes are kinetoplastids that cause many serious human diseases. • African sleeping sickness • Chagas

47. Pyrrophyta • The “fire” protists • Their DNA do not contain the common protein histone • They have bioluminescence • One such group is the Dinoflagellates

48. Dinoflagellates

49. Dinoflagellates

50. Dinoflagellates • Typically photosynthetic • Some non-photosynthetic parasitic forms exist • Typically Planktonic • Typically unicellular • Two flagella that beat within perpendicular grooves. • Cause red tides, an explosive growth. These dinoflagellates produce a neurotoxin that is concentrated by shellfish.