11.11.2 Diversity of Vertebrate Species

Question 1

Diversity of Vertebrate Species

Answer 1

• Vertebrates are characterized by a neural crest, an internal skeleton, and a muscular digestive system.
• Vertebrates are divided into two superclasses: Agnatha or jawless vertebrates and Gnathostomata or jawed vertebrates.
• The cartilaginous fishes include sharks and rays and they have a skeleton composed of cartilage.
• The bones of bony fishes have calcium carbonate deposits; the jaws of bony fish are toothed and bony fish have an operculum over their gills and a swim bladder.

Question 2

note

Answer 2

• The monophyletic group, the Vertebrata, is placed at the subphylum level. All vertebrates are characterized by neural crest cells, which invaginate to form the dorsal nerve tube. These cells migrate throughout the vertebrate embryo and contribute to the formation of the axial skeleton and the appendicular skeleton. This skeleton creates support and the capacity for rapid movement.
• The vertebrates are divided into two superclasses: the
  Agnatha are the jawless vertebrates and the Gnathostoma are the jawed vertebrates.
• The Agnatha include hagfishes and lampreys.
• The Gnathostoma include cartilaginous fishes, bony fishes, lobe-finned fishes, lungfishes and tetrapods.
• Hagfish have no cerebrum or cerebellum. They produce voluminous amounts of slime, which causes them to sneeze when it clogs their gills.
• Most lampreys are parasitic on other fish species. The sea lamprey was introduced in the Great lakes and has caused much damage to fisheries in the region.
• The superclass Gnathostomata represents the jawed
  vertebrates. As shown in the illustration on the left, jaws
  probably developed from skeletal rods that supported the pharyngeal arches. At some point some of these arches migrated to the mouth and formed the beginnings of a jaw. Later more arches were incorporated, reinforcing the jaw and allowing for the growth of bony teeth.
• The placoderms are now extinct, but they were the first class of vertebrates to have true jaws. They were probably great predators in the Silurian and Devonian oceans.
• Sharks and rays are members of the class Chondrichthyes. Their skeleton is made of cartilage and they do not have true bony teeth.
• The class Osteichthyes includes the bony fish. They have toothed jaws with true teeth and a bony endoskeleton. The have an operculum, which is a protective covering over the gills. A swim bladder helps bony fish to maintain neutral buoyancy as pressure changes with depth.
• Lobed-finned fish have fins, which are attached to bones. This created the potential for “walking” on land. For many years, lobed-finned fish were thought to be extinct, but an ancient species, the coelacanth, was found in the deep sea off Madagascar.
• The lung fish are probably the ancestor of tetrapods. They have a primitive lung, which is connected to the pharynx of the digestive tract. They live in ponds and swamps in the Southern Hemisphere.
• Tetrapods include all animals that walk on land: amphibians, reptiles, birds and mammals.

Question 3

Which of the following is an example of a tetrapod?

Answer 3

• dog
• bird
• snake
• all of the above

Question 4

All of the following are differences between vertebrates and arthropods except:

Answer 4

• Vertebrates have a coelom, while arthropods do not.

Question 5

True or false?

The jaws of arthropods and the jaws of vertebrates are homologous.

Answer 5

• false

Question 6

What is unique about lobe-finned fish?

Answer 6

• the fins are attached to bone

Question 7

Which of the following groups has no living representatives on Earth?

Answer 7

• Placodermi

Question 8

Hagfishes and Lampreys belong to which superclass?

Answer 8

• Agnatha