Chapter 21

1. Chapter 21

2. Kingdom Protista • This kingdom is also called the protozoan group. • proto = first • zoan= animals

3. Characteristics of Protozoans • Unicellular • Mostly microscopic • All symmetries represented (oval, spherical, etc…) • No organs or tissues, but some specialized organelles; nucleus may be single or multiple • Free-living, commensalism, mutualism, parasitism all present

4. Binary Fission • Binary means “two” • Fission means “splitting” • So Protists that reproduce this way are literally splitting in two.

5. Characteristics of Protozoans • Locomotion by pseudopodia, flagella, cilia, and direct cell movements. • Simple endo- or exo- skeleton, but most are naked. • Nutrition of all kinds: autotrophic, heterotrophic, saprozoic (using nutrients dissolved in the surrounding medium • Aquatic (marine or freshwater) or terrestrial (in moist soil or leaf litter) • Reproduction asexually by budding, fission, or cysts, and sexually by conjugation or syngamy (union of male and female gametes to form a zygote.)

6. The First Eukaryotes • Protists are thought to be the first eukaryotes. • They evolved about 1.5 billion years ago. • Thought to have formed through the process of Endosymbiosis.

7. Endosymbiosis

8. Two important features of eukaryotes that formed first in protists: • Sexual reproduction • Multicellularity

9. What’s the unifying theme of protists? • They are all eukaryotic organisms that can’t be classified as plants, animals, or fungi. (all of the “leftover eukaryotes”) • They do not form embryos during early development.

10. Alternation of Generations: • As with some plants, some protists go through an alternation of generations. • This means that there is a diploid form (has two copies of each chromosome) and another form that is haploid (has only one copy of each chromosome).

11. Alternation of Generations: • The diploid, spore producing phase is called the sporophyte. • The haploid, gamete producing phase is called the gametophyte.

12. Alternation of Generations:

13. Sporophyte • The adult sporophyte produces reproductive cells called sporangia, which produces haploid spores by meiosis. • These spores grow into multicellular haploid gametophytes.

14. Sporangia

15. Gametophyte • The mature gametophytes produce haploid gametes that fuse and complete the life cycle by dividing through mitosis to form a new diploid sporophyte.

16. Conjugation • This is the temporary union of two protists to exchange nuclear material. Conjugation in paramecium

17. Ameobas Ameboid Movement: • Members of the phylum Rhizopoda move by using flexible cytoplasmic extensions called pseudopodia. • pseudo = false • podia = feet

18. Foraminifera • Typically live in sand or attach themselves to other organisms or on rocks. • Characterized by their porous shells, called tests. These shells are made of calcium carbonate. • Long, thin projections of cytoplasm extend through the pores of the tests, in order to catch prey and aid in swimming.

19. Foraminifera

20. Foraminifera

21. Algae • These protists are strict photoautotrophs. • Multicellular and unicellular forms • Major portion of marine plankton

22. Algae • Green – (Phylum Chlorophyta) Contain the same pigments found in the chloroplasts of plants. • Red – (Phylum Rhodophyta) Mostly multicellular. Have pigment that absorbs light waves that penetrate deep water. • Brown – (Phylum Phaeophyta) Mostly marine. Kelp is an example of this phylum.

23. Halosphaera-green algae

24. Red Algae

25. Brown Algae

26. Diatoms • Phylum Bacillariophyta • Photosynthetic • Unicellular • Double shelled • Move by secreting chemicals through holes in their shells, enabling them to glide • Sexual reproduction

28. Diatoms • Sexual reproduction involves separating the shell in halves, and each new diatom generates a new half. The shell becomes too small, after successive “halvings”. • Then the diatom slips out of its shell, grows to normal size, regenerates a new shell, and begins the cycle of reproduction again.

29. Flagellates • These are protists that move using flagella

30. Three kinds of Flagellates: • Dinoflagellates • Euglenoids • Kinetoplastids

31. Dinoflagellates • Freshwater and marine • Have an exterior coat made of cellulose • Various unusual shapes • Usually twin flagella, which beat within two grooves around the body at right angles to one another. • Responsible for “Red Tides” • Usually reproduce asexually • Can be heterotrophic or autotrophic, or both.

32. Dinoflagellates

33. Red Tide

34. Euglenoids • Freshwater protists with two flagella. • About one-third of these are photosynthetic • The other two-thirds are heterotrophic • Has a light sensitive organ called the “eyespot” • Has a flexible protein scaffold called a pellicle, which allows it to change shape • Reproduce by mitosis

35. Euglenoids

36. Kinetoplastids • Unicellular • Heterotrohpic • Have at least one flagella, but some have thousands • Most reproduce asexually, but some sexually • Example is the trypanosomes, like the one that causes African Sleeping Sickness

37. Kinetoplastids

38. Ciliates • Have large numbers of cilia (short hair like projections from the cell membrane, which provide movement for the organism) • Unicellular heterotrophs • Also have a pellicle • Micronuclei and macronuclei • Reproduce sexually and asexually • Paramecium is an example

39. A closer look at paramecium:

40. Protistan Molds: • These are heterotrophs with some mobility • Once thought to be fungi, because of their similar appearance • Contain different carbohydrates than fungal cell walls. • Carry out mitosis, unlike fungi

41. Cellular slime molds • Resemble amoebas • Move through the soil ingesting bacteria • During times of stress, they form aggregations called slugs • Then the aggregates form stalked structures which contain spores • These spores, when released, form new amoeba like organisms

42. Cellular slime molds

43. Plasmodial slime molds • These stream along as a mass of cytoplasm that looks like an oozing slime • They feed on bacteria • Contains many nuclei, but they are not separated by cell walls • Also creates spores in unfavorable conditions • Spores can grow into amoeboid cells or flagellated cells, which can fuse into diploid zygotes

44. Plasmodial slime molds

45. Plasmodial slime molds

46. Other molds • Oomycetes is a phylum of water molds, white rusts, and downy mildews • Often grow on dead animals in freshwater • All members of the group are parasitic or detritivores (feed on dead organisms) • Unusual because they have two flagella, with one facing forward and the other facing backward.

47. Water molds

48. Oomycetes • These organisms are responsible for the failure of potato crops in Ireland in 1845 – 1850 • This crop failure led to a famine that killed about 1 million people!

49. Sporozoans • Parasitic protists that form spores during their reproduction cycle • Nonmotile, unicellular • Malaria is a disease caused by sporozoans • Cryptosporidium is a sporozoan which causes disease, it infected water supplies in several cities in the US in 1980s and 1990s. It comes from pet feces.

50. Cryptosporidium