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Figure 19.18" Exoskeleton and jointed appendages.
Arthropods, such as a lobster, have various appendages attached to the head region of a cephalothorax and five pairs of walking legs attached to the thorax region.
Appendages called swimmerets, used in reproduction and swimming, are attached to the abdomen. The uropods and telson make up a fan-shaped tail.
Figure 19.19" Monarch butterfly metamorphosis.
a. A caterpillar (larva) eats and grows. b. After the larva goes through several molts, it builds a cocoon around itself and becomes a pupa. c. Inside the pupa, the larva
undergoes changes in organ structure to become an adult. d, e. The adult butterfly emerges from the cocoon and reproduces, and the cycle begins again.
Figure 19.23" Echinoderm diversity.
a. Anatomy of a sea star. b. Sea lilies are immobile, but feather stars can move about. They usually cling to coral or sponges where they feed on plankton. c. Sea
cucumbers have a long, leathery body that resembles a cucumber, except for the feeding tentacles about the mouth. d. Brittle stars have a central disk from which long,
flexible arms radiate. e. Sea urchins and sand dollars have spines for locomotion, defense, and burrowing.
Figure 19.22" Insect diversity.
Check Your Progress
Check Your Progress
1. What are unique features of echinoderms?
2.
List the four distinguishing features of chordates.
Answers:" 1. Echinoderms have radial symmetry as adults and a water vascular system with tube feet for locomotion." 2. Chordates have a notochord, dorsal tubular
nerve cord, pharyngeal pouches, and postanal tail.
Figure 19.26" Evolutionary tree of chordates.
Each of the numbered innovations is shared by the classes beyond that point.
Figure 19.24" The four chordate characteristics.
Figure 19.25" Invertebrate chordates.
a. Tunicates (sea squirts) have numerous gill slits, the only chordate characteristic that remains in the adult. b. Lancelets have all four chordate characteristics as adults.
Check Your Progress
1. Explain the evolutionary significance of the development of a jaw.
2.
Among amphibians, what features in particular are adaptations to life on land?
Answers:" 1. The jaw allowed vertebrates to become predators." 2. Amphibians have jointed limbs, eyelids for keeping their eyes moist, ears for picking up sound waves,
a voice-producing larynx, and usually lungs.
Figure 19.29" Evolution of amphibians.
a. A lobe-finned fish compared with an amphibian. A shift in the position of the bones in the forelimbs and hind limbs lifts and supports the body. b. Newt (shown here)
and frogs (see Fig. 19.1) are types of living amphibians.
Figure 19.27" Evolution of jaws.
Jaws evolved from the anterior gill arches of ancient jawless fishes.
Figure 19.28"
Diversity of fishes.
a. The lamprey is a jawless fish. Note the toothed oral disk. b. The shark is a cartilaginous fish. c. The soldierfish, a bony fish, has the typical appearance of a ray-finned
fish.
Figure 19.32" Bird flight.
Birds fly by flapping their wings. Bird flight requires an airstream and a powerful wing downstroke for lift, a force at right angles to the airstream.
Figure 19.33" Bird beaks.
a. A cardinal s beak allows it to crack tough seeds. b. A bald eagle s beak allows it to tear prey apart. c. A flamingo s beak strains food from the water with bristles that
fringe the mandibles.
Figure 19.30" Reptiles.
Snakes wave a forked tongue in the air to collect chemical mole-cules, which are then brought back into the mouth and delivered to an organ in the floor of the mouth.
Analyzed chemicals help the snake trail its prey, recognize a predator, or find a mate.
Figure 19.31" Reproduction on land.
a. A baby American crocodile hatching out of its shell. Note that the shell is leathery and flexible, not brittle like a bird s egg. b. Inside the egg, the embryo is surrounded
by extraembryonic membranes. The chorion aids gas exchange, the yolk sac provides nutrients, the allantois stores waste, and the amnion encloses a fluid that prevents
drying out and provides protection.
Figure 19.35" Placental mammals.
Placental mammals have adapted to various ways of life. a. Deer are herbivores that live in forests. b. Lions are carnivores on the African plain. c. Monkeys inhabit
tropical forests. d. Whales are sea-dwelling placental mammals.
Figure 19.34" Monotremes and marsupials.
a. The spiny anteater is a monotreme that lives in Australia. b. The opossum is the only marsupial in the United States. The Virginia opossum is found in a variety of
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