Biology 80 - Vertebrates

Cyclostomes

• Hagfishes, lampreys

• Jawless fishes

Gnathostomes

• Jawed vertebrates

• Are hypothesized to have evolved by modification of skeletal rods that supported the pharyngeal (gill) slits

Chondrichthyes

• Sharks, rays, skates, and relatives

• Skeleton primarily composed of cartilage

  1. Evolved secondarily from an ancestral mineralized skeleton

• Ampulla a of Lorenzini

  1. Sensory organs that allow detection of electrical fields

• Constantly swimming to move water across gills

  1. Ram ventilation

Osteichthyes

• Bony endoskeleton with a hard matrix of calcium phosphate

Actinopterygii

• Ray-finned fishes

• Includes majority of osteichthyes

• Fins supported by long and flexible bony-rays

  1. Modified for maneuvering, defense, and other functions

Sarcopterygii

• Muscle in pectoral and pelvic fin 

  1. Use to swim and “walk” underwater across the substrate in brackish water and coastal wetlands

Actinistia

• Coelacanths

• One of surviving living lobe-fin lineages

Dipnoi

• Lungfish

• One of surviving living lobe-fin lineages

Tetrapods

• Four limbs and feet with digits

• A neck

  1. Separate movement of the head

• Fusion of pelvic girdle to the backbone

• Absence of gills (except some aquatic species)

• Ears for detecting airborne sounds

Amphibia

• Salamanders, frogs, toads, caecilians

• Means “both ways of life”

  1. Referring to the metamorphosis of an aquatic larva into a terrestrial adult

• Fertilization is external in most species, and the eggs require a moist environment

• Most have moist skin that complements the lungs in gas exchange

• Augmenting cutaneous respiration

  1. Gills

  2. Buccal

  3. Lungs

Amniotes

1. Tetrapods with terrestrially adapted eggs

2. Amniotic egg

   1. Contains membranes that protect the embryo

      1. Amnion, chorion, yolk sac, and allantois

Reptilia

• Birds, lizards, snakes, turtles, crocodilians, scale covering

• Amniotic egg

• Thoracic breathing

• Includes dinosaurs, plesiosaurs, ichthyosaurs, pterosaurs

• Archosaurs (birds)

  1. Adaptations that facilitate flight

     1. Keratin feathers

     2. Lack of urinary bladder, females with 1 ovary/testie, no teeth

  2. Ratites

     1. An order of unique flightless birds

Mammalia

• Milk production by mammary glands

• Hair

• Warmblooded (endothermics)

  1. High metabolic rate

• Larger brain than other vertebrates of equivalent size

• Differentiated teeth

Monotremes

• Egg-laying mammals

• Echidnas and the platypus

Marsupials

• Pouch mammals

• Embryo develops within a placenta in the mother’s uterus

• Born very early

• Continues embryonic development while nursing in a maternal pouch (marsupium)

Eutherians

• Placental mammals

• More complex placenta

• Embryonic development completed in the uterus, joined to the mother by the placenta

Primata-Hominidae

• Great Apes

• Large brain and short jaws

• Forward-looking eyes close together on the face, providing depth perception

• Complex social behavior and parental care

• fully opposable thumbs

Homo sapiens

• Upright and bipedal locomotion

• Larger brains

• Language 

• Symbolic thought

• The manufacture and use of complex tools

• Shortened jaw

• Shorter digestive tract