1. AP Biology
Lecture #47
Protists

2. Protist Systematics & Phylogeny, I
1- Groups lacking mitochondria; early eukaryotic link; Giardia (human intestinal parasite; severe diarrhea); Trichomonas (human vaginal infection)
2- Euglenoids; autotrophic & heterotrophic flagellates; Trypanosoma (African sleeping sickness; tsetse fly)

3. Protozoans Phylum Flagellates
Flagellates have a small number of long flagella, long whiplike hairs that beats to propel the cell.
Trypanosoma, Giardia, etc.
Some nasty parasites are flagellates, including Giardia lamblia, which causes diarrhea and which is found in most of the surface waters of the US. Another is Trypanosoma brucei, which causes sleeping sickness in Africa. Also Trichmonas vaginalis, a sexually transmitted disease.

4. Protist Systematics & Phylogeny, II
Alveolata: membrane-bound cavities (alveoli) under cell surfaces; dinoflagellates (phytoplankton); Plasmodium (malaria); ciliates (Paramecium)

5. Protozoans Phylum Ciliates Cell covered by 1000s of tiny cilia
Swim by waving cilia. The cilia beat in a synchronized pattern to cause movement.
Genetics: the DNA used for sexual reproduction is stored in the small micronucleus. A copy of this information is used to run the cell: the copy is kept in the much larger macronucleus.
Paramecium is a typical ciliate. It has a gullet to swallow food, and a contractile vacuole to get rid of excess water.

6. Protist Systematics & Phylogeny, III
Stamenophila: water molds/mildews and heterokont (2 types of flagella) algae; numerous hair-like projections on the flagella; most molds are decomposers and mildews are parasites; algae include diatoms, golden, and brown forms

7. Protist Systematics & Phylogeny, IV
Rhodophyta: red algae; no flagellated stages; phycobilin (red) pigment
Chlorophyta: green algae; chloroplasts; gave rise to land plants; volvox, ulva

8. The second unicellular algae, Bacillariophyta, are photosynthetic autotrophs.
They have shells of silica.
They make up a large portion of the world’s phytoplankton which is Earth’s largest provider of oxygen.

9. Algae: Phylum Diatoms Other photosynthetic pigments
Cells walls of silica (silicon dioxide), finely ornamented
Variety of shapes

10. The third unicellular algae, Dinoflagellata, are a major component of marine phytoplankton.
These algae have at least two flagella set at right angles to each other and thick cell walls made of cellulose plates.
Blooms of dinoflagellates cause “Red Tide.”

11. Multicellular Algae
The multicellular algae are commonly called seaweed. They can be classified into red, brown, and green algae. All have chloroplasts, but the pigments in the chloroplasts vary, giving the different colors.
Some, like kelp, are very large and contain several different types of cells and tissues to do specialized work. These include leaves for photosynthesis, gas-filled bladders for buoyancy, the root-like holdfast, and tubes to transport nutrients throughout the body.
Algae contain the polysaccharide “agar”, which is tasteless and is used to thicken foods such as soft ice cream.

12. Phylum Phaeophyta is made up of the brown algae.
They are found in cool saltwater along rocky coasts.
Giant Kelp are the largest and most complex brown algae. They have hold fasts and air bladders.

13. Protist Systematics & Phylogeny, V
Affinity uncertain:
Rhizopods: unicellular with pseudopodia; amoebas
Actinopods: ‘ray foot’ (slender pseudopodia; heliozoans, radiolarians

14. Protozoans Phylum Amoeboids calcium carbonate shells
Movement by cytoplasmic streaming (Move by extensions of the cell membrane and cytoplasm called pseudopods or “False Feet”).
Usually no fixed shape
Amoeba,
Foraminferans
calcium carbonate shells

15. Protist Systematics & Phylogeny, VI
Mycetozoa: slime molds (not true fungi); use pseudopodia for locomotion and feeding; plasmodial and cellular slime molds

16. Slime Molds Slime molds have traits like both fungi and animals
Slime Molds Slime molds have traits like both fungi and animals. During good times, they live as independent, amoeba-like cells, dining on fungi and bacteria. But if conditions become uncomfortable—not enough food available, the temperature isn't right, etc.—individual cells begin gathering together to form a single structure. The new communal structure produces a slimy covering and is called a slug because it so closely resembles the animal you sometimes see gliding across sidewalks. The slug oozes toward light. When the communal cells sense that they've come across more food or better conditions, the slug stops

17. Slime molds
Slime molds obtain food through decomposition of organic material
This is a slime mold--> commonly found on grass. It’s called the dog vomit slime mold – eewww, gross!

18. Water molds from the Phylum Oomycota are classified as protists because they have flagellated reproductive cells.
Downy mildews parasitize plants and are decomposers in freshwater ecosystems.

20. “cloning” – plants identical to each other
Isogamy = male and female gamete identical in size
Sexual reproduction- create variation

24. Protist Diversity Parasitic & pathogenic Protists malaria Giardia
trypanosomes
Plasmodium
African Sleeping Sickness and South American Chagas Disease
Giardia
Trypanosoma

25. Protozoans Phylum Apicomplexans Plasmodium causes malaria
Sporozoans are animal-like protists that have part of their life cycle inside the cells of their hosts. Non-motile
Parasites that feed on the cells and fluids of a host animal.
They reproduce and spread by spores.
Obligate parasites
Plasmodium causes malaria
Toxoplasma in cats

26. Protist Diversity Beneficial & necessary Protists phytoplankton
small algae + diatoms
much of the world’s photosynthesis
produces ~90% of atmospheric oxygen
zooplankton
heterotrophic protists + animals
key ecological role at base of marine food web
Mmmmmm! Sounds like breakfast!