Chapter 34

Subphylum Vertebrata

• Vertebrates
• Chordates with a backbone

Chordate features as well as:

1. Vertebral column
   • Series of cartilaginous or bony elements
2. Cranium
3. Endoskeleton or cartilage or bone
4. Hox genes (lots of them)
5. Neural crest

Cyclostomes

• Jawless Fishes

Class Myxini

• Hagfishes
• lack jaws, eyes, fins vertebrae
• skeleton comprised of notochord and cartilaginous skull
• covered in slime

Class Cephalospidomorphi

• Lampreys
• Has notochord, and cartilaginous vertebral column
• lacks jaws and appendages (fins)
• Oldest fossil records 510 mybp

Class Chondrichthyes

• Cartilaginous fishes
• Sharks, skates, rays
• Cartilaginous skeleton and notochord as adults
• jawed fishes
• paired appendages (fins)
• < 900 species

Class Osteichthyes

• Bony fishes
• Most diverse vertebrate group with  < 26,000 species
• Bony skeleton (most do have this)
• Jawed
• paired appendages (fins)

Tertapod: Gnathastomes

• Four limbs with jawed mouth
• Transition to land involved adaptions for locomotion, reproduction, desiccation (drying out) prevention, and gas exchange
• Sturdy lobe-finned fishes became animals with four limbs
• Vertebral column strengthened, ship and shoulder bones braced against backbone
• relatively simple changes in gene expression, especially Hox genes

Class Amphibia

• >4000 species
• Amphibios
  • greek - "living double life"
  • split their life between aquatic and terrestrial stages
• Successfully invaded land but reproduce in water
• Lunges are and adaption to semi-terrestrial lifestyle
• Three chambered heart
  • Fishes only have a two chambered heart
• External Fertilization
• Larval stages are aquatic
  • Undergo metamorphosis
• Not completely separated from water

Order Anura

• Frogs and toads
• Nearly 90% of amphibians
• Carnivorous adults
  • Herbivorous tadpoles

Order Apoda

• Caecilians
• Nearly blind tropical burrowers
• Secondarily legless

Order Urodela

• Salamanders
• Often have colorful skin patterns
• Most have four limbs

Amniotes

• Tetrapods with a desiccation resistant egg
• Critical innovation
  • Development of a shelled egg
• Amniotic egg
  • Broke the tie to water
  • Three internal membranes
• Shell is permeable to Oxygen and CO2
  • Birds
    • Hard and Calcareous
  • Reptiles
    • Soft and Leathery
  • Most Mammals
    • Embryo embeds in uterine wall
    • Only three species lay eggs
      • These eggs are soft and leathery

Other Key Innovations of the Amniotes

• Desiccation resistant skin
  • contains keratin
• Thoracic breathing
  • Negative pressure sucks air in 
• Water conserving Kidneys
  • Concentrate waste prior to elimination
• Internal fertilization

Class Reptilia

• >8000 living species
• turtles, crocodilians, lizards, snakes
• Can live away from water
• thicker skin and scales
• larger brain
• larger limbs with muscles
• enhanced kidneys
• Amniotic egg
  • "indoor pond"

Vertebrate Reproductive Modes

1. Oviparous
   • Egg laying outside of the body
2. Ovoviviparous
   • live baring wuth retention of eggs
   • No maternal connection
3. Viviparous
   • live bearing with egg retained
   • Maternal connection

Class Aves

• Birds
• Evolved form small dinosaurs
• Fossils 150mybp
• Adaptions for flight
  • Feathers
  • Modified front limbs
  • Lightweight skeleton
  • Organ reduction
  • Lungs and air sacs
    • more gas exchange
• Oviparous
  • all leg layers
• Bill beak
  • Encloses mouth and nasal cavity
  • Adapted for environment

Endothermic

• "Internal temperature"
• Body temperature is primarily controlled by trapped metabolic heat.
• Birds and mammals

Ectothermic

• "External temperature"
• Body temperature is primarily related to external temperature
• Metabolic heat is generated but difficult to capture/maintain the heat
• Fishes, amphibious, reptiles

Class Mammalia

• Milk producing Amniotes
• Evolved from amniote ancestors (reptiles) earlier than birds
• >6000 species
• Appeared ~ 225mybp
  • Evolved from small mammal-like reptiles
• After dinosaur extinction, mammals flourished
• Range of sizes, body forms, and complexity unmatched

• Fish-like mammals
  • Marine mammals
• Bird-like mammals
  • Bats
• Reptile-like mammals
  • Three egg layers

Distinguishing Characteristics

• Mammary Glands
  • Secrete milk
• All have hair
  • In varying amounts
• Only vertebrate with multiple dentitions
  • Heterodont
    • Different types of teeth 
    • incisors, canines, molars, premolars
  • Thecodont
    • Teeth with long roots embedded in sockets of jawbone
  • Diphyodont
    • Milk teeth that are mostly replaced by "adult" teeth later in life
• Pinna
  • Flap of cartilage and lose connective tissue to channel and funnel sound
  • The "outer ear"
• Three middle ear ossicles (bones)
• Enlarged Skull
  • Brain enlarged in large skull
  • Larger Cerebrum
  • Single lower Jawbone (Dentary)
• Anucleate red blood cells

Order Primates

• Primarily tree dwelling species
• grasping hands with  opposable thumbs
• Large brain
• Some digits with flat nails
  • Not claws
• Binocular vision
• Complex social behavior and well-developed parental care 
• Enhanced sense of touch

Taxonomy of Humans

• Kingdom Animalia
  • Phylum Chordata
    • Subphylum Vertebrata
      • Class Mammalia
        • Order Primates
          • Suborder Anthropoidea
            • Superfamily Hominoidae
              • Family Hominidae
                • Subfamily Homininae
                  • Tribe Hominini
                    • Genus Homo
                      • Species Homo sapiens