ASIM'S WEBWORLD View: Main School Main AP Biology Chapter Guides RELATED LINKS Chapter Outline		AP BIOLOGY: Chapter Forty-Two Review Answers 1. The three primary characteristics are a single, hollow dorsal nerve cord; a dorsal notochord; and pharyngeal gill slits. The three subphyla are Urochordata (tunicates), Cephalochordata (lancelets), and Vertebrata (vertebrates). 2. In the vertebrates, bony vertebrae replace the notochord. The nerve cord is protected within a U-shaped groove in the vertebrae. 3. The seven classes of vertebrates are as follows: Agnatha (lampreys, hagfishes), Chondrichthyes (sharks, rays, skates), Osteichthyes (bony fish), Amphibia (frogs, toads, salamanders), Reptilia (reptiles), Aves (birds), Mammalia (mammals). 4. An advantage to possessing jaws is that it encourages active predation; it also improves the ability to collect food over sucking or filtering it. Jaws are a modification of one or more gill arches. Teeth are modified from skin. 5. The bony skeleton weighs more so that fish tend to sink with it. An air bladder provides buoyancy to counter the sinking. This bladder developed from a lunglike outpocketing of the pharynx. 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 are 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 dessication. 8. Modern amphibians are characterized by the presence of legs, cutaneous respiration, lungs, pulmonary veins, and a partially-divided heart. Salamanders and newts have tails; frogs and toads lack tails as adults; and caecilians lack legs. 9. Modern reptiles are characterized by the presence of amniotic eggs, dry skin (covered with scales), and thoracic breathing. Reptiles also have internal fertilization, a partially divided ventricle in the heart, and are cold-blooded. The four living orders of reptiles are the Chelonia (turtles and tortoises), the Rhynchocephalia (tuataras), the Squamata (lizards and snakes), and the Crocodilia (crocodiles and alligators). 10. The egg is an amniotic egg, which protects the embryo from drying out, nourishes it, and enables the development of the embryo independent of free water. Nutrients are in the yolk, and wastes are excreted into the allantois and stored until hatching. Respiration is through the shell and membranes, which are permeable to oxygen and carbon dioxide. 11. Birds differ in that their forelegs have evolved into wings and their bodies are covered with feathers. They have light, hollow bones; and they have highly efficient lungs. Feathers are derived from scales. 12. Amphibian legs jut out from the sides of the body, reptilian legs are straightened and tentlike, and mammalian legs are located directly beneath the body. The mammalian arrangement of legs facilitates running. 13. Mammals are distinguished from the other vertebrates by the presence of hair or fur and milk-producing glands for the purposes of nourishing the young. Mammals are also endothermic, providing for the ability of continuous activity through day and night and alternating seasons. (1) Mammals are also characterized by a placenta, an organ that provides nourishment and removes wastes from the internally-developing live embryo. (2) Mammalian teeth are retained through life (i.e., are not continuously replaced, the way a shark's are) and are typically highly modified to fit the feeding ecology of the animal. (3) Herbivorous mammals have modified digestive tracts, permitting them to make full use of cellulose as a diet. (4) Other mammals have modified keratinous structures such as horns and hooves, providing important adaptation for climbing, fighting, and protection. (5) Some mammals (bats) have evolved the ability to fly, allowing mammals to exploit a niche typically unavailable to other mammals. 14. Monotremes are mammals such as the duck-billed platypus that lay eggs. Marsupial mammals such as kangaroos give birth to immature young, which complete development in a special external pouch on the surface of the mother. Placental mammals complete the fetal development of the young completely within the mother, facilitated by the placenta. Placental animals are born alive.