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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 48 (p. 980)

1. The four primary characteristics are a single, hollow dorsal nerve cord, a dorsal notochord, pharyngeal gill slits, and a postanal tail.

2. The three subphyla are Urochordata (tunicates), Cephalochordata (lancelets), and Vertebrata (vertebrates).

3. In the vertebrates, bony vertebrae replace the notochord.

4. An advantage to possessing jaws is that it encourages active predation; it also improves the ability to collect food compared to sucking or filtering it. Jaws are a modification of one or more gill arches.

5. The bony skeleton weighs more so that fish tend to sink with it.

6. The lateral line system is the ability to detect changes in the pressure of water and sense movements of objects. Pressure waves created by objects moving in the surrounding water deflect cilia on hair cells that send positional information to the brain.

7. The five major innovations were as follows: (1) Legs were necessary to support the body’s weight. (2) Lungs were necessary because the delicate structure of fish gills requires the buoyancy of water to support it. (3) The heart had to deliver greater amounts of oxygen required by walking muscles. (4) Reproduction had to be carried out in water, until ways could be found to prevent the eggs from drying out. (5) Techniques had to be developed to prevent the body from desiccation.

8. Nutrients are in the yolk and wastes are excreted into the allantois and stored until hatching.

9. Feathers are derived from scales.

10. Amphibian legs jut out from the sides of the body, reptilian legs are straightened and tent-like, and mammalian legs are located directly beneath the body.

11. There are a number of characteristics that distinguish dogs and cats. Some are behavioral. Others are variable and exceptions easily come to mind. A definitive difference that can be determined, even if the animal is dead, is the number of teeth. Dogs have 42 teeth, including 4 canine teeth. Cats have only 30 teeth, including 4 canine teeth.