1. Biology, 9th ed, Sylvia Mader
Chapter 22
Chapter 22
The Protists
The Protists

2. Protist Diversity, cont.
Outline
Protist Biology
Protist Evolution
Protist Diversity
Green Algae
Red Algae
Brown Algae
Diatoms
Dinoflagellates
Protist Diversity, cont.
Euglenoids
Zooflagellates
Pseudopods
Ciliates
Sporozoans
Slime Molds
Water Molds

3. General Biology of the Protists
Classified into the Domain Eukarya & the Kingdom Protista
Morphology:
Most unicellular
Many with amazingly high level of strucrural and functional complexity
Life cycles:
Asexual reproduction common
Sexual reproduction may occur when conditions deteriorate
Some life cycles simple, many extremely complex

4. Origin of the Eukaryotic Cell

5. Ecology of Protists Protists are of enormous eco-logical importance
Photoautotrophic forms:
Produce oxygen
Function as producers in both freshwater and saltwater ecosystems
Major component of plankton
Organisms that are suspended in the water
Serve as food for heterotrophic protists and animals
Many protists are symbionts
Ranges from strict parasitism to mutualism
Coral reefs greatly aided by symbiotic photoautotrophic protists in tissues of corals

6. Complexity and diversity of protists makes them difficult to classify
Evolution of Protists
Complexity and diversity of protists makes them difficult to classify
Many classification schemes proposed
None has broad support
Cannot be classified as plants, animals, or fungi
Could be split into as many as a dozen kingdoms
The scheme chosen for this discussion is based on modes of nutrition

7. Protist Diversity

8. Diversity of Protists: Green Algae – The Chlorophyta
Phylum Chlorophyta
Approximately 7,500 species
Inhabit a variety of environments including oceans, freshwater, snowbanks, tree bark, and turtles backs
Many are symbionts with fungi, plants, or animals
Morphology varied
Majority unicellular, but many are filamentous or colonial
Some are multicellular and resemble leaves of lettuce
Plants thought to be derived from Chlorophyta because both groups:
Have a cell wall that contains cellulose
Possess chlorophylls a and b, and
Store excess food as starch

9. Green Algae: Chlamydomonas
A minute (<25 μ m), actively moving flagellate
Inhabits still, freshwater pools
Fossil ancestors date back over a billion years
Anatomy:
Definite cell wall
Single, large, cup-shaped chloroplast
Chloroplast with a pyrenoid where starch is synthesized
Many with a bright red eyespot, or stigma on chloroplast
Two long, whip-like flagella
Project from the anterior end
Operate with a breaststroke motion

10. Electron Micrograph of Chlamydomonas

11. Green Algae: Chlamydomonas
Most often reproduces asexually
As many as 16 daughter cells within parent cell
Escape by digesting the parent cell
Occasionally reproduces sexually
Gametes fuse to form a zygote
Becomes a heavy-walled, resistant zygospore
Goes into a period of dormancy
Upon germination produces four zoospores by meiosis
“Spore” - a reproductive cell that develops into a new organism without fusing with another cell
“Zoospore” - flagellated spores, typical of aquatic species

12. Reproduction in Chlamydomonas

13. Green Algae: Spirogyra
Filamentous green algae
Found in green masses on the surfaces of ponds and streams
Has ribbon-like, spiraled chloroplasts
Sexual reproduction by conjugation:
A temporary union during which the cells exchange genetic material
Two filaments line up parallel to each other
Cell contents of one filament move into the cells of the other filament
Forms diploid zygospores
In spring, undergo meiosis to produce new haploid filaments

14. Spirogyra

15. Green Algae: Multicellular Forms
Ulva
Multicellular green alga
Commonly called sea lettuce
Thallus (body) is two cells thick
Can be as much as a meter long
Sexual cycle involves alternation of generations
Similar to higher plants, except
Both generations look exactly alike, and
The gametes all look the same

16. Multicellular Green Algae

17. Green Algae: Colonial Forms
Volvox
A colony is a loose association of independent cells
A Volvox colony:
A hollow sphere
Thousands of cells arranged in a single layer surrounding a watery interior
Each cell of colony resembles a Chlamydomonas cell
Flagella beat in a coordinated fashion
Some cells are specialized for reproduction
Each can divide asexually to form a new daughter colony within the parental colony
Leaves parental colony by releasing an enzyme that dissolves away a portion of the parental colony

18. Volvox

19. Diversity of Protists: Red Algae – The Rhodophyta
Multicellular
About 5,000 species
Live mostly in warmer seawater, some as deep as 200 m
Economic Importance
Agar - capsules; dental impressions; cosmetics; culture medium; electrophoresis; food prep.
Carrageen - an emulsifying agent used in chocolate, low-fat foods, & cosmetics
The reddish-black wrappings around sushi rolls consist of processed Porphyra blades

20. Red Algae

21. Diversity of Protists: Brown Algae – The Phaeophyta
About 1,500 species
Most live in colder ocean waters along rocky coasts
No unicellular or colonial brown forms
Morphology:
Some small forms with simple filaments
Others large multicellular forms that may exceed 200 m in length
Pigments:
Chlorophylls a and c
Fucoxanthin (a type of carotinoid pigment) gives them their color
Excess food stored as a carbohydrate called laminarin

22. Brown Algae

23. Multicellular forms of green, red, and brown algae are called seaweeds
The Phaeophyta
Multicellular forms of green, red, and brown algae are called seaweeds
Laminaria (a kelp), and Fucus, (rockweed), are common intertidal seaweeds
Nereocystis and Macrocystis often form forest-like thickets in deeper waters
Sargassum forms floating masses where other organisms find shelter
Harvested for food and fertilizer
Macrocystis is source of algin, a thickener for foods

24. Laminaria shows tissue differentiation
The Phaeophyta
Laminaria shows tissue differentiation
Transport organic nutrients in a tissue resembling phloem
Life cycle
Most brown algae have alternation of generations
In some species of Fucus
Meiosis produces gametes instead of spores
The adult is always diploid, as in animals

25. Diversity of Protists: Yellow-green Algae – The Chrysophyta
Diatoms (formerly Bacillariophyta) are the most numerous unicellular algae in the oceans
Significant portion of phytoplankton
Cell wall
Two valves, with the larger valve acting as a lid (like a mint tin)
Contains silica
Diatomaceous earth used as
Filtering agents
Sound-proofing materials
Polishing abrasives

26. Diversity of Protists: Dinoflagellates – The Pyrrophyta
About 4,000 species of unicellular aquatic and marine organisms
Morphology:
Cell is usually bounded by protective cellulose plates impregnated with silicates
Typically with two flagella
One in a longitudinal groove with its distal end free
The other lies in a transverse groove that encircles the organism
Symbiotic dinoflagellates in corals called zooxanthellae
Dinoflagellates provide their host with organic nutrients
Corals provide wastes that fertilize the algae
Some lack chloroplasts and are parasitic
Gymnodinium brevis may cause “red tide”
Produce a powerful neurotoxin that has caused massive fish kills
Consume shellfish during outbreak can cause respiratory paralysis

27. Diatoms and Dinoflagellates

28. Fish Kill and Dinoflagellate Bloom

29. Diversity of Protists: The Euglenoids – Phylum Euglenophyta
Small freshwater unicellular organisms
Difficult to classify
Have two flagella and an eyespot (shades a photoreceptor)
One flagellum much longer than the other
Projects out of an anterior, vase-shaped invagination
Called a tinsel flagellum because of hair-like projections
Cell bounded by flexible pellicle
Chloroplasts:
Surrounded by three rather than two membranes
With a pyrenoid which produces an unusual type of carbohydrate called paramylon

30. Euglena

31. Diversity of Protists: Zooflagellates – Phylum Zoomastigophora
Colorless heterotrophs
Most symbiotic and many parasitic
Well known for causing various diseases in humans
Trypanosoma
African sleeping sickness - Tsetse fly
Chagas disease – Kissing bug
Giardia lamblia
Most common flagellate in human digestive tract
Causes severe diarrhea
Cysts are transmitted in contaminated water
Beavers are important reservoir hosts
Trichomonas vaginalis
Sexually transmitted protist,
Infects urogenital organs; a common cause of vaginitis

32. Zooflagellates

33. Giardia lamblia

34. Diversity of Protists: Protists with Pseudopods
Pseudopods form when cytoplasm streams forward in a particular direction
Amoeboids (phylum Rhizopoda) are protists that move and ingest their food with pseudopods
Phagocytize food
Entamoeba histolytica - a parasite of the human colon;
Causes amoebic dysentery
Can be fatal
Foraminiferans (phylum Foraminifera) and radiolarians (phlyum Actinopoda)
Both have a skeleton (test) of either calcite or silica

35. Protists with Pseudopods

36. Diversity of Protists: The Ciliates – Phylum Ciliophora
Ciliates (phylum Ciliophora) are among the most complex of the protozoans
Hundreds of cilia beat in coordinated rhythm
Most are holozoic, swallowing food whole
Divide by transverse binary fission during asexual reproduction
Two nuclei of differing types
Micronucleus – Heredity
Macronucleus – Metabolism

37. Ciliates

38. Diversity of Protists: The Sporozoans – Phylum Apicomplexa
Nonmotile obligate parasites
Most serious parasitic disease of human is malaria
Plasmodium spp
Kills 3,000,000 people each year
Transmitted by mosquito
Toxoplasma
Humans get from cats
Causes birth defects and mental retardation when pregnant mom exposed

39. Life Cycle of Plasmodium vivax

40. Diversity of Protists: Slime Molds
Plasmodial Slime Molds - Phylum Myxomycota
Body in the form of a plasmodium
Diploid, multinucleated, cytoplasmic mass
Enveloped by a slimy sheath
Eventually produces sporangium which in turn produces spores
Cellular Slime Mold - Phylum Acrasiomycota
Body in the form of individual amoeboid cells
Later aggregate into pseudoplasmodium which then forms sporangium & spores

41. Plasmodial Slime Molds

42. Diversity of Protists: Water Molds - Phylum Oomycota
Most live in the water
Phylum name refers to the enlarged tips (called oogonia) where eggs are produced
Body filamentous, appearing like true Fungi
Cell walls largely of cellulose rather than chitin
The organism is diploid (not haploid as in the fungi)
Phytophthora infestans caused the 1840’s potato famine in Ireland
Saprolegnia is often seen as a white, cotton-like coating on dead aquarium fish

43. Water Mold

44. Protist Diversity, cont.
Review
Protist Biology
Protist Evolution
Protist Diversity
Green Algae
Red Algae
Brown Algae
Diatoms
Dinoflagellates
Protist Diversity, cont.
Euglenoids
Zooflagellates
Pseudopods
Ciliates
Sporozoans
Slime Molds
Water Molds

45. Biology, 9th ed, Sylvia Mader
Chapter 22
Ending Slide Chapter 22
The Protists
The Protists