|
Summary |
|
Questions |
|
Media
Resources |
|
48.1 Attaching muscles
to an internal framework greatly improves movement.
|
|
• The
chordates are characterized by a dorsal nerve cord and by the presence,
at least early in development, of a notochord, pharyngeal slits, and a
postanal tail. In vertebrates, a bony endoskeleton provides attachment
sites for skeletal muscle.
|
|
1. What are
the four primary characteristics of the chordates?
|
|
|
|
48.2 Nonvertebrate
chordates have a notochord but no backbone.
|
|
• Tunicates
and the lancelets seem to represent ancient evolutionary Chordate offshoots.
|
|
2. What are
the three subphyla of the chordates? Give an example of each.
|
|
|
|
48.3 The vertebrates
have an interior framework of bone.
|
|
• Vertebrates
differ from other chordates in that they possess a vertebral column, a
distinct and well-differentiated head, and a bony skeleton.
|
|
3. What is
the relationship between the notochord and the vertebral column in vertebrates?
|
|
|
|
48.4 The evolution
of vertebrates involves invasions of sea, land, and air.
|
|
• Members
of the group Agnatha differ from other vertebrates because they lack jaws.
• Jawed fishes are active swimmers and dominant in fresh
and salt water everywhere.
• The first land vertebrates were the amphibians. Amphibians
are dependent on water and lay their eggs in moist places.
• Reptiles were the first vertebrates fully adapted
to terrestrial habitats. Scales and amniotic eggs represented significant
adaptations to the dry conditions on land.
• Birds and mammals were derived from reptiles and are
now among the dominant groups of animals on land. The members of these
two classes have independently become endothermic, capable of regulating
their own body temperatures; all other living animals are ectothermic,
their temperatures set by external conditions.
• The living mammals are divided into three major groups:
(1) the monotremes, or egg-laying mammals, consisting only of the echidnas
and the duck-billed platypus; (2) the marsupials, in which the young are
born at a very early stage of development and complete their development
in a pouch; and (3) the placental mammals, which lack pouches and suckle
their young.
|
|
4. What is
one advantage of possessing jaws? From what existing structures did jaws
evolve?
5. What is the primary disadvantage of a bony skeleton compared
to one made of cartilage?
6. What is the lateral line system in fishes? How does it function?
7. The successful invasion of land by amphibians involved five
major innovations. What were they, and why was each important?
8. How does the embryo obtain nutrients and excrete wastes while
contained within the egg?
9. From what reptilian structure are feathers derived?
10. How do amphibian, reptile, and mammal legs differ?
11. Exactly how would you distinguish a cat from a dog? (be specific)
|
|
|
