1. Kingdom Protista
AP Biology – Ch. 28

2. Introduction to the Protists
Earliest Eukaryotes
Arose about 1 billion years before the first true plants, animals or fungi
Earliest protist fossils are around 2.1 billion years old
The first billion years of eukaryote evolution appears to have produced several very divergent lineages
For Example: some are animal-like, some plant-like and some fungus-like…

3. Protists are EXTREMELY DIVERSE
The ONLY thing that ALL protists share in common is that they are ALL EUKARYOTES
Protists are considered to be the simplest eukaryotic organisms, HOWEVER…
At the cellular level, many protists are extremely complex
Otherwise, diversity is the “rule”
Cellularity: most are unicellular, but some are colonial and some are multicellular
Animal-like, plant-like, fungus-like characteristics
60,000 different species!

4. dinoflagellates & ciliates
Great Diversity
dinoflagellates & ciliates
brown algae & diatoms
euglenoids
red algae
green algae
miscellaneous?

5. 3 Groupings of Protists
Keep in mind that these groupings have NO taxonomic significance…
This means that these groupings do not imply true evolutionary relationships, but are just a convenient way to talk about members of this incredibly diverse and poorly organized kingdom

6. 3 Groupings of Protists Animal-like Protists The Protozoans
Called animal-like because they ingest food (like animals)
Includes members like amoeba, paramecium, etc.

7. 3 Groupings of Protists Fungus-like Protists
These are organisms that obtain nutrition from “absortption” of nutrients from the environment…like fungi do.
Includes members like slime molds

8. 3 Groupings of Protists Plant-like Protists
Also called photosynthetic protists or ALGAE
Includes organisms like Volvox and Kelp.
All algae share the photosynthetic pigment chlorphyll a in common.
Differ in their accessory pigments

9. Movement in Protists Most protists (though NOT all) are motile
Most protists have either cilia or flagella at some point in their life cycle
Remember that eukaryotic and prokaryotic flagella are NOT homologous
Euk. – extensions of cytoplasm; bundles of microtubules (9+2) covered by cell membrane
Prok. – “crank” mechanism attached to cell surface

10. Reproduction in Protists
Reproduction is highly varied among protists
Mitosis does occur in most protists
Protists may be asexual or sexual reproducers
Protists may produce cysts
Resistant cells that can survive harsh conditions
Something like a bacterial endospore

11. Where Protists are Found
Anywhere there is water.
Maybe just moisture…

12. Some Important Protist Groups
Plankton
Communities of organisms that drift passively or swim weakly at the water’s surface
Basis of marine and freshwater food chains is phytoplankton
Phytoplankton account for ½ of all photosynthesis
Free living protists
Symbiotic protists
Implies mutualistic or beneficial relationships
Parasitic protists
Host is harmed

13. Origin of Eukaryotic Cells from Prokaryotes
Many structures are unique to eukaryotic cells
Membrane enclosed nucleus
Mitochondria
Chloroplasts ER
Cytoskeleton
9+2 flagella
Multiple linear chromosomes
Two processes are thought to have led to the origin of these structures in eukaryotes….

14. Origin of Eukaryotic Cells from Prokaryotes – 2 processes
Endomembrane System (ER) may have evolved from infoldings of the prokaryotic cell membrane
Endosymbiosis
Mitochondria and chloroplasts were once small prokaryotes
Became involved in a symbiotic relationship with larger cells

15. Origin of Eukaryotic Cells from Prokaryotes – Endosymbiosis
Ancestors of mitochondria – Aerobic heterotrophic prokaryotes
Ancestors of chloroplasts – photosynthetic prokaryotes (probably cyanobacteria)
May have entered larger cell as undigested prey or as internal parasites
Provided host with nourishment
Such endosymbiotic relationships are observed today

16. Origin of Eukaryotic Cells from Prokaryotes – Additional Evidence Supporting the Endosymbiotic Hypothesis
Chloroplasts and mitochondria are both the appropriate size to be descendents of bacteria
Inner membranes of chloroplasts and mitochondria have enzymes and transport systems similar to modern prokaryotes
Mitochondria and chloroplasts replicate by a process similar to binary fission
Both contain a circular DNA molecule that is not associated with histone proteins
Ribosomes in both are more like prokaryotes than eukaryotes

17. Origin of Eukaryotic Cells

18. Kingdom Protista is BAD Taxonomy/Systematics
Kingdom Protista has been a “dumping ground” for organisms that did not fit nicely into any of the other eukaryotic kingdom
Kingdom Protista is Paraphyletic = made up of organism groups that do NOT share a common ancestor
Kingdom Protista is now considered obsolete
Scientists are working on sorting out the members of Protista into 5 new “candidate kingdoms” that are all monophyletic
Remember: monophyletic – all members come from one common ancestor

19. Problems with Protist Classification
Too Diverse!
doesn’t reflect any evolutionary relationship amongst all kingdom members
paraphyletic
Euglenozoa
Animals
(includes land plants)
Streptophyta
Choanoflagellida
Fungi
Chlorophyta
Rhodophyta
Stramenopila
Alveolata
Archaea
Bacteria
Something’s not right here!

20. New Protist Classification (from 6th ed.)
1 Kingdom
Split into
8 Kingdoms?

21. “Candidate Kingdom Archaezoa”
Uniting characteristic of these members:
All lack mitochondria
Called archaezoa to emphasize their ancient ancestry
The lineages of these protists go back to before the endosymbiotic creation of mitochondria

22. Candidate Kingdom Euglenozoa
Common characteristic of all Euglenozoans is flagella
Most members are autotrophic, but may also be heterotrophic (by absorption or ingestion)
Euglenoids and Kinetoplastids
Famous parasite in this group:
Trypanosoma
Causes African Sleeping Sickness
Two hosts required: TseTse Fly and Human

23. Euglena
Click HERE to see Euglena Movies

24. Trypanosome
Click HERE for more on Trypanosomes

25. Candidate Kingdom Alveolata
Common characteristic:
all possess small membrane bound cavities (alveoli) under their cell surfaces
Contains 3 large groups
Dinoflagellates
Photosynthetic flagellates
Apicomplexans
parasites
Ciliates
All members move by means of cilia

26. Dinoflagellates Found in phytoplankton at ocean’s surface
Responsible for Red Tides
Toxins produced by dinoflagellates cause massive fish kills and may harm humans also
Pfiesteria
Characteristics
Cellulose cell plates – “armor”
2 flagella perpendicular to each other
Results in spinning motion

27. Dinoflagellates

28. Apicomplexans ALL parasites Used to be called sporozoans Famous member
Plasmodium
Causes malaria
2 hosts required
Mosquito
Human
Liver and blood cells

30. Ciliates All have cilia Most live as solitary cells in fresh water
2 nuclei
Micronucleus
Required for sexual process
Not involved in maintenance, growth or other routine functions
Macronucleus
Controls everyday functioning of the cell

32. Reproduction in ciliates
Mostly binary fission
Macronucleus splits (NO mitosis)
Sometimes conjugation
Micronucleus is exchanged between individuals
No REPRODUCTION – no “babies - just exchange of genes
Meiosis and syngamy (fusion of genetic material) do occur in the micronucleus

33. Conjugation

34. Protists that Use Pseudopods Classification not certain according to your text
Amoebas etc. are in this group that does not have a “candidate kingdom” yet.
Pay attention to feeding and locomotor mechanisms

35. Pseudopods Extensions of cytoplasm Used for movement and feeding
Organisms that use pseudopods are generally heterotrophs. They eat:
Bacteria
Other protists
Detritus (decaying matter)
May also be PARASITES

36. Groups of Protists with Psueudopods
Rhizopods
The amoeba
Actinopods
“ray foot” – possess rays or extensions
Foraminiferans
Calcium carbonate shells

37. The Rhizopods Amoeba ALL unicellular Can move directionally (taxis)
Reproduce asexually only
Both freshwater and marine habitats
Some can be parasitic – amoebic dysentery spread by contaminated food, water, etc.
Click HERE to see an amoeba movie

39. The Actinopods
“ray foot” - Named for the slender pseupodia that radiate from them (axipodia)
Internal skeleton
Plankton
Microorganisms stick to the axipodia and are phagocytized.

40. The Actinopods Includes the heliozoans Includes the radiolarians
Freshwater
Silica (glassy) or chitin skeletons
Includes the radiolarians
Mostly marine
Silica skeletons
At death, skeletons of actinopods sink to the seafloor where the accumulate into “ooze” that is hundreds of meters thick in places.

41. Foraminiferans All marine Named for porous shells
Made of calcium carbonate
Strands of cytoplasm extend through pores in shell

42. Candidate Kingdom Myceteozoa (actually a newly added 6th candidate kingdom)
The Slime Molds
Plasmodial Slime Molds
Cellular Slime Molds
Basic Characteristics
Resemble fungi
Appearances ONLY due to CONVERGENT evolution – NOT homologies
Closest relatives of the slime molds are probably the amoebas

43. Plasmodial Slime Molds
Brightly pigmented
Orange and yellow
Heterotrophic
Two body forms
One for obtaining food
The other for reproductioin

44. Plasmodial Slime Molds
Plasmodium – the amoeboid mass that acts as the feeding stage of the slime mold
Can get several cm large
Actually unicellular!
Cytoplasmic streaming helps distribute nutrients and oxygen throughout the slime mold.
Engulfs food via phagocytosis

45. Plasmodial Slime Molds
If food source is gone or conditions become poor for the plasmodium…
It ceases growth
Differentiates into a stage that functions in sexual reproduction

46. Cellular Slime Molds
Feeding stage composed of solitary cells that function individually
When food is depleted, the cells for an aggregate the functions as a unit.
The cells always maintain their individual identity which is different from the plasmodial slime mold
Haploid cells dominate (only zygote is diploid)
Fruiting bodies function in asexual reproduction

47. Cellular Slime Molds – life cycle

48. Cellular Slime Mold - Stages

49. Candidate Kingdom Stramenopila
Includes photosynthetic autotrophs and some heterotrophs
Common characteristic is fine hair-like projections on flagella
Evidence suggests that the photosynthetic members of this kingdom did NOT get their c-plasts from the cyanobacteria like all other photoautotrophs
Instead theirs are descended from red algae

50. Photosynthetic Members of Kingdom Stramenopila
Diatoms
Yellow/brown
Walls are made of silica and an organic matrix
Shoebox and lid
Shells make sediments called diatomaceous earth
Filtering medium; abrasive (toothpaste!)

51. Diatom Photos

52. Photosynthetic Members of Kingdom Stramenopila
Golden Algae
2 flagella attached at one end of the cell
Can absorb or ingest food particles
mixotrophic
Some colonial species

53. Photosynthetic Members of Kingdom Stramenopila
Brown Algae
Multicellular
Marine
Kelp
Called Seaweeds
This title is also used to refer to green and red algae

54. Photosynthetic Members of Kingdom Stramenopila
More on seaweeds / kelp
Inhabit intertidal zones – very challenging
60 meters long
Cell walls gelatinous to help cushion against waves
Food source and…
Thickeners for pudding, salad dressing, ice cream
Also lubricants
Complex structures are ANALOGOUS to plants
Thallus – plant-like seaweed body
Holdfast – root like structure; anchors plant
Stipe – stem-like structure
Blades – leaf-like structure
Air-filled floats – hold blades up toward light

55. Kelp

56. Kelp Life Cycle

57. Hetertrophic Members of Kingdom Stramenopila
Oomycota
Water molds – most are decomposers (often seen on dead aquarium fish)
White rusts – plant parasite
Downy mildew – plant parasite
All heterotrophic
Filaments/hyphae are analogous to fungi, cell walls are made of cellulose (NOT chitin)
Diploid is dominant form – haploid is dominant in fungi
Have flagellated cells – fungi don’t
Large egg fertilized by a small sperm

58. Water Mold Life Cycle
Water mold on
Dead fish

59. Candidate Kingdom Rodophyta – Red Algae
No flagella – but did not evolve before flagella existed
DNA analysis suggests that red algae are not that ancient. Flagella were lost during evolution
Accessory pigment (phycobillins) make the red
Red absorbs short waves of light most efficiently
These are the only waves that make it to deep water
Red algae will appear very dark at great depths but be almost green in shallower water
The deeper the algae the redder its color

60. Red Algae

61. Red Algae

62. Candidate Kingdom Chlorophyta?
Green Algae
Classification is still in question
Separate from plants or with plants?
Certainly the plants and the green algae share a common ancestor
Chloroplasts are very similar

63. Green Algae 7000 species Most are freshwater
Some even enter into a mutualistic relationship with fungi to form a lichen
May be unicellular, colonial or multicellular
Complex life histories (repro cycles)
Most reproduce by way of biflagellated gametes
Some even use amoeboid gametes

64. Examples of Green Algae
Chlamydomonas
Primitive species
All life stages haploid except zygote

65. Chlamydomonas Life Cycle

66. Reproductive Modes Observed in Green Algae
Isogamy
Fusion of gametes of similar size
Anisogamy
Fusion of gametes of different size
Oogamy is one type
Egg is large and non motile; sperm flagellated

67. Multicellularity Arose Many Times
More variations are possible for complex structures than simpler ones
Evolution of eukaryotes broke one barrier to diversification – Multicellularity broke another
The link between unicellular and multicellular organisms is colonial organisms
Division of Labor
Different cells take on different jobs and become very proficient at those jobs
Example: loss of flagella in some cells combined with more efficient performance of other cell functions