Chapter Summary

1. There is evidence that all living organisms were confined to the ocean less than 1 billion years ago. It is believed that green algae began making the transition from water to land about 400 million years ago and gave rise to land plants.

2. Kingdom Protista includes many diverse organisms that all have eukaryotic cells. Members may be unicellular or multicellular and occur as either colonies or filaments. Modes of nutrition include photosynthesis, ingestion of food, a combination of both, or absorption of food in solution. Some members are nonmotile, but most are motile.

3. Green algae (Chlorophyta) have cells with the same pigments and reserve food (starch) as those of higher plants. The chloroplasts of Chlamydomonas have pyrenoids; the cells have two or more vacuoles and often a red eyespot. Asexual reproduction is by mitosis; sexual reproduction is isogamous.

4. Ulothrix is a filamentous green alga that may be attached to objects by means of a holdfast; each cell contains a curved plate chloroplast around the periphery. Asexual reproduction is by zoospores; sexual reproduction is isogamous.

5. Spirogyra is a floating, filamentous green alga with spiral, ribbonlike chloroplasts. Asexual reproduction is by fragmentation. Sexual reproduction is by conjugation.

6. Oedogonium is an epiphytic, filamentous green alga; it has cylindrical, netted chloroplasts. In asexual reproduction, zoospores are produced. Sexual reproduction is oogamous.

7. Other green algae include Chlorella, desmids, Acetabularia,Volvox,Ulva, and Cladophora.

8. The several classes of Chromophyta include the yellow-green algae, the true golden-brown algae, the diatoms, and the brown algae. Some members produce statospores.

9. Diatoms are very abundant; they have a glassy shell that consists of two "halves" that fit together like a box with a lid.

10. Fucoxanthin gives a golden-brown color to most chromophytes. Some diatoms move by contact of the cytoplasm with a surface as it protrudes through the pores.

11. Diatoms reproduce asexually by mitosis and sexually through the fusion of gametes that form an auxospore (zygote).

12. Many brown algae (Phaeophyceae) are large seaweeds; their thalli often may be differentiated into a stipe, flattened blades, and a holdfast.

13. The color of brown algae is largely due to fucoxanthin; the main carbohydrate food reserve is laminarin. Some brown algae produce algin, a useful gelatinous substance. The reproductive cells have lateral flagella. The common rockweed, Fucus, produces eggs and sperms that form zygotes in the water.

14. Most red algae (Rhodophyta), represented by Polysiphonia, are seaweeds with life cycles that involve three different types of thalli and nonmotile gametes.

15. Red and blue phycobilins are partially responsible for the colors of red algae; chlorophyll d may be present in the chloroplasts. The main carbohydrate food reserve is floridean starch. Some red algae produce agar, an economically important gelatinous substance.

16. Euglenoids (Euglenophyta) have no rigid cell wall, one functional flagellum, a gullet, and paramylon as a carbohydrate food reserve. Reproduction is by cell division. Sexual reproduction has not been confirmed.

17. Dinoflagellates (Dinophyta) are unicellular organisms with two flagella inserted at right angles to each other. Some cause red tides that can kill fish and poison humans. Dinoflagellates in tropical waters exhibit bioluminescence (emission of light) when disturbed.

18. The cryptomonads (Cryptophyta) are biflagellated, unicellular algae with two chloroplasts and an extra vesti-gial nucleus (nucleomorph).

19. Haptophytes (Prymnesiophyta) have biflagellated cells with a flagellumlike haptonema that aids in the capture of food.

20. Stoneworts (Charophyta) are branched green organisms that superficially resemble horsetails.

21. Algae are ecologically and economically important. Diatomaceous earth is used for filtering, polishes, insulation, and reflectorized paint. Chlorella is a potential food and oxygen source. Algin is used as a stabilizer and thickening agent in hundreds of products.

22. Some brown algae are a source of fertilizer, iodine, and food. Red algae are a source of agar and food and have potential medicinal value.

23. The plasmodial slime molds, which are animal-like in their vegetative state, consist of a multinucleate mass of protoplasm called a plasmodium that flows over damp surfaces, ingesting food particles.

24. Slime molds form stationary sporangia that contain spores from which myxamoebae or swarm spores emerge upon germination. Myxamoebae or swarm spores function as gametes, with new plasmodia developing from the zygotes.

25. Cellular slime molds produce a pseudoplasmodium that crawls like a slug and can convert to a stationary, sporangium-like mass of spores.

26. Water molds have coenocytic mycelia and include organisms that cause diseases of fish and other aquatic organisms. Asexual reproduction involves zoospores; gametes are produced in oogonia and antheridia.