Chapter 34

Subphylum Vertebrata

Vertebrates
Chordates with a backbone

Chordate features as well as:

Vertebral column
- Series of cartilaginous or bony elements
Cranium
Endoskeleton or cartilage or bone
Hox genes (lots of them)
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

Oviparous
- Egg laying outside of the body

Ovoviviparous
- live baring wuth retention of eggs
- No maternal connection

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

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