KEY CONCEPT All vertebrates share common characteristics.

1. KEY CONCEPT All vertebrates share common characteristics.

2. tail hollow nerve cord notochord pharyngeal slits The phylum Chordata contains all vertebrates and some invertebrates. • Chordates share four features at some stage of development. • notochord • hollow nerve cord • pharyngeal slits • tail

3. tail hollow nerve cord notochord pharyngeal slits • Most chordates lose some or all of these characteristics in adulthood.

4. All vertebrates share common features. • An endoskeleton allows vertebrates to grow to large sizes. • internal • made of bone or cartilage

5. An endoskeleton can be divided into four parts. • braincase (cranium) braincase • vertebrae • bones • gill arches (in fish and some amphibians) vertebrae bones

6. There are seven classes of vertebrates. • Agnatha are jawless fish. • Cartilaginous and bony fish are characterized by the presence of jaws. • Amphibians are characterized by the presence of four limbs. • Reptiles, birds, and mammals are characterized by the presence of an amnion. • Birds are characterized by the presence of feathers. • Mammals are characterized by the presence of hair.

7. Agnatha Chondrichthyes Osteichthyes Amphibia Mammalia Aves bony fish birds lamprey amphibians mammals cartilaginous fish FEATHERS Feathers insulate birds from the cold and allow for flight. FOUR LIMBS Four limbs let animals move from the water to life on land. JAWS Jaws helped vertebrates to become successful predators. HAIR Hair helps mammals to maintain constant body temperatures by roviding insulation from the cold. VERTEBRAE Vertebrates have a segmented backbone.

8. Fossil evidence sheds light on the origins of vertebrates. • Tunicates may be the closest relatives to vertebrates. • The first recognizable vertebrates were jawless fish. • Two groups of jawless fish still exist today. • lampreys • hagfish