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Biology, 6/e
Author Dr. George B. Johnson, Washington University
Author Dr. Peter H. Raven, Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer, Carleton College
Contributor Dr. Jonathan Losos, Washington University


Answers to Review Questions

Chapter 35 (p. 718)

1. Three classes of biochemically distinct chloroplasts in algae and plants suggest origins from different photosynthetic bacteria. The pigments contained in red algae most resemble those of cyanobacteria. The pigments in green algae most resemble the photosynthetic bacterium, Prochloron. The pigments of brown algae and other photosynthetic protists appear to come from yet another source.

2. The Protista have been grouped together for convenience, rather than grouped together because of evolutionary relationships to one another.

3. Mitosis is unique in this group because it takes place solely within the nucleus, and chromosomes include very small amounts of histones. Red tides are population explosions of dinoflagellates, which produce toxins harmful to vertebrates but not to the shellfish that concentrate them. Zooxanthellae are a symbiotic form of dinoflagellate found in jellyfish, sea anemones, and mollusks.

4. A collection of individuals is truly multicellular if there is a division of labor among the cells so that certain of them perform very specialized functions.

5. The members of Ciliophora have cilia arranged in longitudinal rows or spirals around the body, unique among the protists. The two vacuoles are (1) a food vacuole, which digests food particles, and (2) a contractile vacuole, which regulates water balance.

6. Some species of trypanosomes have evolved mechanisms to change their glycoprotein coats, thus making development of a vaccine against specific antigens impossible.

7. Fungi have chitinous cell walls, whereas oomycetes have cellulose walls. They are saprobes or parasites and are distinguished from other protists because they have zoospores with unequal flagella. They are considered harmful because they cause disease in aquatic plants and animals and caused the potato blight responsible for the infamous Irish potato famine.