THE VERTEBRATES

THE VERTEBRATES

1. CHORDATES WITH A BACKBONE

   • Vertebrates have several Characteristics
     • Vertebral column, cranium, endoskeleton of cartilage or bone, neural crest, and internal organs
   • early-diverging vertebrates
     • Lacked Jaws
       • Only jawless vertebrates are hagfish and lampreys

2. JAWED VERTEBRATES

   • Critical innovations
     • Hinged Jaw
       • First Developed in fishes, Gnathostjomes
   • Chondrichthyans
     • have skeleton composed of flexible cartilage and powerful appendages called fins
     • Acute senses and were among the earliest to develop teeth
   • Bony Fish
     • Actinopterygii (ray finned fishes)
       • fins are supported by thin flexible rays and moved by muscles inside the body
     • Actinistia (coelacanths)
     • Dipnoi (LungFish)
   • Lobed-finned
     • Actinistia and Dipnoi and the tetrapods
     • fins are supported by extensions of the pectoral and pelvic areas and are moved by their own muscles

3. TETRAPODS: GNATHOSTOMES WITH FOUR LIMBS

   • Amphibians
     • Live on land but return to the water to reproduce
     • The larval stage undergoes metamorphosis, losing gills and tail for lungs and limbs

4. AMNIOTES: TETRAPODS WITH A DESICCATION RESISTANT EGG

   • Amniotic egg
     • Permitted animals to become fully terrestrial
     • Desiccation resistant skin, thoracic breathing, water conserving kidneys and internal fertilization
     • Key characteristics of Birds
       • feathers
       • lightweight skeleton
       • Air sacs
       • reduces organs

5. MAMMALS: MILK PRODUCING AMNIOTES

   • Distinguishing Characteristics
     • Mammary Glands, Hair, Specialized Teeth, Enlarged Skull
     • Ability to digest plants and horns or antlers
   • SUBCLASSES
     • Prototherian (monotremes)
     • Theria (the live-bearing Mammals
       • Megatheria (Marsupials)
       • Eutheria (Placentral Mammals)
         • Divided into four different clades
   • Characteristics of Primates
     • Grasping hands, large brains, nails instead of claws, and binocular vision
   • Out Of Africa
     • the migration of hominins from afirca happened atlast three times
       • Homo Sapiens gradually replacing other hominid species
   • Multi regional Hypothesis
     • proposes that human groups evolved in number of different parts of the world
   • Data from human mitochondrial DNA suggest all humans derive from a "mitochondrial Eve" that originated in eEast Africa