The Vertebrates

Chordate Evolution

The “Fish” Actually made up of 6 vertebrate classes Hagfish eel-like without jaws, paired fins or bone. No vertebrae either Lamprey like a hagfish but with a primate vertebral column of cartilage

Cartilaginous fish Shark, rays, skates and ratfish Have jaws, bones & paired fins. Skeleton made up of cartilage Unique scales on skin Lobed – fin fish Lungfish and coelacanth Mostly extinct Ancestors to amphibians Fins supported by main axis of bones

The “fish” you know and love Bony fish (Ray finned fish) Jaws, paired fins and a skeleton of bone Fins supported by rays of bone from central axis Lungs (in a few) or swim bladder (controls buoyancy). Gills in most Scales covered by mucus (reduces friction)

More fish characteristics Closed circulatory system w/ a series of blood vessels and a 2 chambered heart Ventricles – muscular chambers to pump blood Atrium – collecting chambers In fish, oxygen-rich and oxygen-poor blood mix then go to the gills for oxygenation (again). From the gills, blood goes to the body Ectothermic External control of body temperature

Reproduction in fish Separate sexes Sperm produced in testes, eggs in ovaries Basically external fertilization and development High mortality rate for eggs and young If all the cod eggs in the world were fertilized and made it to becoming adults, in 2 years, the oceans would be solid cod!

Amphibians Ectothermic Frogs, Toads, Salamanders and Mudpuppies and Newts Aquatic larvae but terrestrial adults Moist, thin skin w/o scales Feet are webbed w/o claws Use gills, lungs and skin for respiration Eggs lack multicellular membranes or shells Ectothermic

3 chambered heart 2 atria and 1 ventricle. Blood still mixes when it goes to the lungs and the body

Separate sexes External fertilization and development Metamorphosis in frogs Eggs hatch and develop into a tadpole Tadpoles are herbivorous Legs and arms develop as tail is absorbed Adults are carnivorous

Reptiles Snakes, crocodiles, alligators, turtles, lizards and caymans Body covered with dry scales Terrestrial Breathe through lungs with alveoli Ectotherm

3.5 chambered heart (crocs have a 4 chambered heart) 2 atria 1.5 ventricles with a septum partially dividing the sides Septum helps to separate the oxygen rich and oxygen poor blood Oxygen poor blood goes to the lungs to be oxygenated and then back to the heart to be pumped to the body

The Amniotic Egg A big moment in evolution!! Allowed for fetal development out of water

Three patterns of reproduction Oviparity - Female lays fertilized eggs Most reptiles, all birds & 3 species of mammals Ovoviviparity – Fertilized eggs remain in body for a short time. Pit vipers, some shark Viviparity – No shell forms & young retained in body until mature. Oxygen and nutrients are transferred across a placenta Placental mammals

Birds Feathers Wings Hollow boned skeleton Endothermic – can control their internal temperature Lungs Oviparity

The 4 chambered Heart A double pump 2 atria and 2 ventricles Septum separates 1 right and left ventricles Oxygen rich and oxygen poor blood never mix Right side pumps deoxygenated blood from the body to the lungs Left side receives oxygenated blood from the lungs and pumps it to the entire body

Parental care Birds are the first time we see extended parental care given to their young Young are born helpless and need long periods of care and development before they can leave the nest.

Mammals Endothermic Hair 4 chambered heart Double pump Mammary glands Extensive care given to young Lungs Specialized teeth (incisors, canines, premolars and molars)

The Human Heart

Three Subclasses Monotremes Duck-billed platypus, echidna Oviparous – thin, leathery shells Echidna incubate eggs in leathery pouch on belly Marsupials Kangaroo, koala, opossum, Tasmanian devil Embryo develop for short time in uterus then emerge & go into marsupian to complete development

3. Placental Mammals Viviparous – give birth to live young Embryo gets nourishment via a placenta through the umbilical cord After birth, young feed on milk via mammary glands Internal fertilization, internal development