1. The Origin and Diversification of Eukaryotes
Chapter 20
The Origin and Diversification of Eukaryotes

2. 20.1 Eukaryotes Acquired Features from Both Archaea and Bacteria
Eukaryotes that are not plants, animals, or fungi are called protists
Scientists believe came from the fusion of prokaryotes due to endosymbiosis

3. Eukaryotes arose in several steps
The origin of a flexible cell surface
The origin of a cytoskeleton
The origin of a nuclear envelope
The appearance of digestive vacuoles
The acquisition of certain organelles via endosymbioisis

5. Protista Video

6. 20.2 Major Lineages of Eukaryotes Diversified in the Precambrian

7. Characteristics of the Protists:
Range from unicelluar to multicellular
All are eukaryotic
Some free-living and some symbionts
Nearly all are aerobic
Some are photoautotrophs with chloroplasts; others are heterotrophs others combine photosynthesis and eating

8. Characteristics of Protists (continued)
Most have cilia or flagella at some time in their life cycles
All can reproduce asexually; others can also reproduce sexually
Mitosis occurs in most
Some have elaborate cells even though unicellular; e.g., Paramecium

9. Alveolates have sacs under their plasma membranes
Alveolates-possess sacs called alveoli under their membranes which play a role in supporting the cell surface
All are unicellular and most are photosynthetic
Dinoflagellates, Apicomplexans, and Ciliates

10. Alveolates

11. Dinoflagellates Have protective cellulose plates
Most have two flagella—one in a longitudinal groove with distal end free and the other in a transverse groove that encircles the organism
Extremely numerous in the oceans
Most are heterotrophic

12. Dinoflagellates continued
Some live as symbionts in invertebrates; e.g. coral
2 genera cause “red tides” and produce a neurotoxin that can kill fish and paralytic shellfish poisoning in humans

13. Figure 28.12 A dinoflagellate

14. Figure 28.12x1 Dinoflagellate

15. Figure 28.12x2 Swimming with bioluminescent dinoflagellates

16. Apicomplexans
Derive there name from the apical complex which is a mass of organelles contained in the apical end (Helps invade host’s tissues)
Helps Plasmodium invade tissues to causes malaria
Plasmodium and Toxoplasma are parasites

17. Apicomplexans

18. Ciliates
Named for their hairlike cilia which a like flagella but shorter
Have two types of nuclei
Almost all are heterotrophic
Most common is the Paramecium

19. Ciliates
Contractile Vacuole-A specialized vacuole that collects excess water taken in by osmosis, then contracts to expel the water from the cell
Digestive Vacuole-An organelle specialized for digesting food ingested by endocytosis

20. Figure 28.14c Ciliates: Paramecium

21. Figure 28.14x Ciliates: Stentor (left), Paramecium (right)

22. Figure 28.15x Paramecium conjugating

23. Paramecium

24. Excavates began to diversify about 1.5 billion years ago
Lack mitochondria and lost them as they evolved
Shows eukaryotic life is possible without a mitochondria
Include: Diplomonads and Parabasalids, Heteroloboseans, and Euglenids and Kinetoplastids

25. Excavates

26. Diplomonads and Parabasalids
Unicellular and lack mitochondria
Causes contaminated water and diseases in humans

27. Diplomonads and Parabasalids

28. Heteroloboseans
Has an amoeboid body and can turn into a life cycle with a flagella

29. Euglenids and Kinetoplastids
Unicellular, freshwater organisms
Some have chloroplasts; the rest ingest food
If grown in darkness, lose chloroplasts and become heterotrophic
Have stored food in pyrenoid in form of a carbohydrate polymer paramylon
Bounded by a pellicle which is flexible to allow changes in shape

30. Figure 28.03x Euglena

31. Figure 28.3 Euglena: an example of a single–celled protist

32. Figure 28.11x Trypanosoma, the kinetoplastid that causes sleeping sickness

33. Stramenopiles typically have two unequal flagella, one with hairs
Include the diatoms and the brown algae which are photosynthetic
Also Oomycetes which are not

34. Diatoms
Most numerous unicellular algae in oceans and are abundant in fresh water
Have cell walls of silica and many geometric shapes
Reproduce both sexually and asexually

35. Figure 28.17 Diatoms: Diatom diversity (left), Pinnularia (left)

36. Figure 28.17x Diatom shell

37. Brown algae
Both brown and golden brown algae have chlorophylls a and c
Range from small forms with simple filaments to large multicellular forms we call seaweeds
Provide food and habitat for marine organisms and are harvested for human food and fertilizer

38. Figure 28.1d Too diverse for one kingdom: Australian bull kelp (Durvillea potatorum)

39. Figure 28.20x2 Kelp forest

40. Figure 28.20x1 Kelp forest

41. Water molds - oomycetes
Usually live in water and parasitize fish
Others live on land and parasitize insects and plants
One species caused Irish potato famine in 1840s
Have cell walls of cellulose; fungi have chitin
Saprobic-feed on dead organic matter

42. Figure 28.16 The life cycle of a water mold (Layer 3)

43. Figure 28.16x2 Water mold: Oogonium

44. Figure 28.x2 Powdery mildew

46. Rhizaria typically have long thin pseudopods
Include Cercozoans, Foraminiferans, and Radiolarians
Unicellular and mostly aquatic
Pseudopods allow for movement

47. Cercozoans Very diverse group with many forms and habitats

48. Foraminiferans Secrete external shells of calcium carbonate
Some live as plankton and others live on the seas floor
Form much of the world’s limestone

50. Figure Foraminiferan

51. Radiolarians
Have thin pseudopods which are structured with microtubules
Help them stay afloat in the ocean
Well know for when they shed their endoskeletons

52. http://micro. magnet. fsu. edu/micro/gallery/radiolarians/radiohead

53. Figure 28.27x Radiolarian skeleton

54. Figure 28.27 Actinopods: Heliozoan (left), radiolarian (right)

55. Amoebozoans use lobe-shaped pseudopods for locomotion
Three groups loboseans, plasmodial slime molds and cellular slime molds

56. Loboseans
Small Amoebozoans that feed by phagocytosis engulfing with the pseudopod
Live in the bottom of lakes and ponds
Most are predators, parasites, or scavengers

57. Figure 28.1a Too diverse for one kingdom: Amoeba proteus, a unicellular "protozoan"

58. Figure 28.26 Use of pseudopodia for feeding

59. Plasmodial (acellular) Slime Molds
Consist of a multinucleated mass, a plasmodium
Phagocytizes decaying plant material
Develops sporangia during unfavorable conditions
Coenocyte-many nuclei enclosed in a single plasma membrane

60. Figure 28.29x1 Plasmodial slime mold

61. Figure 28.1c Too diverse for one kingdom: a slime mold (Physarum polychalum)

62. Figure 28.29 The life cycle of a plasmodial slime mold, such as Physarum

63. Figure 28.29x2 Slime mold Sporangia

64. Cellular Slime Molds Consist of individual ameboid cells
During unfavorable conditions cells aggregate into pseudoplasmodium
Sporangium produces spores that release haploid ameboid cells

65. Figure 28.30 The life cycle of a cellular slime mold (Dictyostelium)

66. Figure 28.30x1 Dictyostelium life cycle

67. Slime Mold Video
The difference between Plasmodial or acellular slime molds and cellular slime molds is that cellular slime molds have separated nuclei. Plasmodial slime molds create a mass with multiple nuclei

68. 20.3 Protists reproduce sexually and asexually
Protists produce asexually by:
Binary fission-one cell into two
Multiple fission- one cell into multiple
Budding-outgrowth of a new cell from a previous one
Sporulation-formation of a spore that is able to grow into a new organism
Clonal lineages-Asexually reproduced groups of nearly identical organisms

69. Some protists reproduce without sexual reproduction
Parmecia go through the process of conjugation
This is when two individuals line up tightly against each other and fuse
Genetic material is exchanged creating a micronucleus
Meiosis and mitosis also take place
Not a form of reproduction just a sexual process of genetic recombination

70. Figure 28.15x Paramecium conjugating

71. Some protist life cycles feature alternation of generations
Alternation of generations-The succession of multicellular haploid and diploid phases in some sexually reproducing organisms
The haploid organism, the diploid organism, or both may also reproduce asexually

72. Morphology may or not different in alternation of generations
Heteromorphic-the two generations differ morphologically
Isomorphic-they do not differ

74. The gamete producing generation does not produce gametes by meiosis because it is haploid
Specialized cells of the diploid spore-producing organism, called sporocytes, divide meiotically to produce four haploid spores
Gametes can only produce new organisms by fusing with other gametes

76. 20.4 Protists Are Critical Components of Many Ecosystems

77. Phytoplankton are primary producers

78. Some microbial eukaryotes are deadly

79. Some microbial eukaryotes are endosymbionts

80. Coral Bleaching (Protists dying)

81. We rely on the remains of ancient marine protists