Kingdom protista

1. Name means “the very first” (Greek) Is a “catch all” kingdom for eukaryotes that are not plants, animals or fungi Divided into categories based on the way they obtain food --- Plantlike (autotrophs), animal-like (internal digestion), fungus-like (external digestion) Does not reflect evolutionary relationships. May one day be separated into >1 kingdom Kingdom protista

2. PROTISTs • Eukaryotic - most unicellular. There are a few multicellular forms. • Unlike bacteria, protists have a very complicated internal structure. • Protists can be divided into • plant-like: algae (including seaweed), diatoms • animal-like (protozoa) • Flagellated (Giardia), Euglena has characteristics of plant & animal • Ciliated (Paramecia, Euplotes) • Ameboid (amoeba species) – use pseudopods or “false feet” • fungus-like (slime molds, etc.) • includes many common plant pathogens such as Phythophthora, cause of the Irish Potato famine

3. Animal-like Protists • Most are free-living. These are classified according to how they move: amoeba-like, ciliated, or flagellated. • Others are parasitic ; phylum Sporozoa includes Plasmodium which causes malaria. See life cycle page 503. • Amoeba-like protists move by extending cytoplasm into pseudopods, then pulling the rest of the cell along behind. They can surround and engulf their food this way = phagocytosis • Some amoeba-like protists have hard shells. The foraminiferans are covered in calcium carbonate—chalk, which we use on chalk boards.

4. Amoebas in Action

6. Plant-like protists • Autotrophs. Most of the oxygen we breathe came from algal photosynthesis. • Very important commerical uses. • Thickener (algin) • Most are single-celled, but a few form large multicellular seaweed species. Some used in food preparation (sushi, etc.) • Some, such as the diatoms, have calcium carbonate (chalk) or silica shells. • Important applications for gardeners

7. Green Algae • Proposed ancestors of modern plants. • Some algae species are unicellular (such as Chlamydomonas), some form simple colonies (such as Volvox), and some are relatively complex multicellular organisms (such as Acetabularia). • Green algae are haploid most of their live cycle, with only a very short diploid phase.

8. Algal Blooms • sudden growth of a large population of single celled algae • occurs near coastlines, where the algae feed on fertilizer runoff and sewage • Algae blooms deplete the oxygen in the water, killing fish and other organisms. • Some of the algae also secrete toxins. Red tide and Pfiesteria are examples.

9. Multicellular Algae • commonly called seaweed • can be classified as 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 tissue. 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.

10. Plant-like protist: euglena • Has features of a plant … chloroplasts • Allows it to make its own food • Has features of an animal … • “eyespot” to detect light vs dark • “flagellum” allows it to move

11. Day 1 summary • Protista is a catch-all category for eukaryotes that don’t fit anywhere else in the classification system. • They are classified first by how they feed: • Plant-like (autotrophs) • Animal-like (internal digestion) • Fungi-like (external digestion) • Animal-like are further divided by how they move. • Plant-like (algae) are classified by the color of their pigments. • x

12. Fungus-like Protists • Include some of the worst plant diseases. • Phytphthora infestans causes rot in plants. In the 1840’s, Phytophthora caused the potato blight in Ireland. • Caused crop failures over several years, resulting in much death and emigration.

13. Fungus-like Protists • Water molds and slime molds • Heterotrophic; many are decomposers of dead organisms. • Unlike fungi, the fungus-like protists produce motile (moving) cells during part of their life cycle. Also, these protists surround and engulf bacteria as food. • Slime molds live as separate cells most of their lives, feeding on bacteria. When conditions get harsh, they aggregate into a multicellular slug, which migrates to a new location. The slug then forms a fruiting body that generates spores. The spores from the fruiting body are very hardy.

14. Animal-like protists: Ciliated • Cilia beat in a synchronized pattern to cause movement. • Example: Paramecium • Paramecium is a typical ciliate. It has a gullet to swallow food, and a contractile vacuole to get rid of excess water. • Genetics: the DNA used for sexual reproduction is stored in the small micronucleus. A copy of this information is used to run the cell.

16. Animal-like Protists: Flagellated • Flagellates have a small number of long flagella, long whiplike hairs that beats to propel the cell. • Some nasty parasites are flagellates, including Giardialamblia, which causes diarrhea and which is found in most of the surface waters of the US. Another is Trypanosomabrucei, which causes sleeping sickness in Africa. Also Trichmonasvaginalis, a sexually transmitted disease.

17. Animal-like Protists: parasites • Sporozoans are animal-like protists that have part of their life cycle inside the cells of their hosts. • Ex: Plasmodium causes malaria which kills 1-2 million people each year. • Mosquitoes are the vector. • Plasmodium reproduces sexually in mosquito gut and asexually inside the human red blood cells, destroying them as they leave.