Vertebrates Phylum Chordata 4 basic characteristics 1 2

Vertebrates

Phylum Chordata 4 basic characteristics: 1. 2. 3. 4. Notochord – supporting rod dorsally located, below the nerve cord, replaced by vertebral column in most chordates Nerve cord – anterior portion becomes brain, rest spinal cord Pharyngeal pouches – only seen during embryonic development, gills in aquatic vertebrates. In humans, 1 st pair = auditory tubes, 2 nd = tonsils, 3 and 4 th pair = thyroid and parathyroid Postanal tail – in embryo if not in adult

Nonvertebrate chordates o o Notochord persists in adults Lancelets n n o marine, few centimeters long retain 4 chordate characteristics as adult Sea squirts (tunicates) n n n live on ocean floor squirt water in defense Retain gills as adult

Vertebrates o o o At some stage in life history, have all four chordate characteristics Living endoskeleton with vertebral column Closed circulatory system Paired appendages Efficient respiration and excretory High degree of cephalization

Fishes o Evolution n n Jawless – agnathans, lamprey jaws o o Cartilaginous – sharks, stingrays Bony n n Lobe finned – coelacanths, thought to give rise to amphibians Ray finned – soldier fish, lionfish, seahorse, swordfish

Fish Characteristics o o o o Aquatic ectotherms – depend on environment to regulate body temp Skin covered with scales Fins for swimming Single loop cardiovascular pathway, 2 chambered heart Breath with gills Lay eggs Swim bladder seen in bony fish, buoyancy

Amphibians o o Live on both land water 3 main groups n n n Salamanders and newts –elongated bodies, long tails Frogs and toads - tailless Caecilians – legless, sometimes sightless, worm shaped

Amphibian characteristics o o o o Usually tetrapod – 4 legged Usually lungs in adults Metamorphosis Smooth and moist skin 3 chambered heart Ectothermy Most lay eggs in water

Reptiles o Amniotic egg evolves n o Extraembryonic membranes – protect the embryo, remove nitrogenous wastes and provide the embryo with oxygen, food and water Crocodiles and alligators, turtles, lizards, snakes, amphisbaenians (worm lizards) and tuataras

Reptile characteristics o o o Usually tetrapods Lungs with expandable rib cage Leathery-sheled amniotic egg – allows for movement to land Dry, scaly skin that is impermeable to water Ectotherms – can lay in sun to maintain a warm body temperature

Birds - Aves o o o Some fly, some do not Usually classified according to beak and foot type Efficient nervous, respiratory, and circulatory systems.

Bird characteristics o o o Feathers Hard shelled amniotic egg 4 chambered heart Usually wings for flying Air sac endothermy

Mammals - development o Monotremes – mammals have a cloaca and lay hard shelled amniote eggs n o Marsupials – begin development inside the female body and born in a very immature condition, move to pouch and attach to nipple n o Duckbill platypus and spiny anteater Kangaroo, koala, wombat Placental mammals – Eutherians - dependent on the placenta (organ of exchange between maternal blood and fetal blood) n Long dependency on the parents

Mammal characteristics o o o o Body hair Differentiated teeth Well-developed brain Usually live births and newborn dependency Mammary glands Endothermy Internal development