Vertebrates l Jawless fishes to Mammals l Gills

Vertebrates l Jawless fishes to Mammals l Gills to Lungs l Fish – one way circulation l Amphibians – circulation loop l Reptiles – partial septum - little mixing of blood l Mammals and Birds – completely divided

Fish Classes • Agnatha – Jawless fish, evolved about 540 MYA. Ex. Lamprey • Chondrichthyes – cartilaginous fishes. Ex. Sharks and rays • Osteichthyes – bony fish • Gills for respiration

Agantha - Lamprey

Jaw evolution

Sharks l Fast, powerful predators, l Lateral line system – sensory organs running down the side of the body for detecting vibrations in the water

Chondricthyes

Bony Fish l Hard skeleton with scales l Protective operculum over the gills l Swim bladder for buoyancy l Ray finned fish – most bony fish like the tuna, bass, perch l Lobed finned fish – ancestor to the amphibians

Osteicthyes

Perch anatomy

Lobed finned fish

Fish circulation

Amphibians l Living a double life – part water/part land l Gas exchange through diffusion l Complete metamorphosis l Partially divided heart l Ex. Salamander, frogs

Amphibians

Amphibian circulation

Reptiles Watertight skin and eggs Internal fertilization – no water needed Ectothermic Scales made of keratin Lungs Dinosaurs were numerous during the Mesozoic era l By about 65 MYA, the dinosaurs were gone, with only the birds left. l Turtles, crocodiles, lizards and snakes l l l

Reptile Heart

Reptiles

Archaeopteryx

Birds l Class Aves l Evolved during the mesozoic era l Honeycombed bones for lighter weight l Wings for flight, feathers made of keratin l Endothermic – warmed by own metabolism l No teeth, grind food with gizzard

Birds

Mammals l Became diverse after the downfall of the dinosaurs l Hair and mammary glands l Endotermic l Monotremes – duck-billed platypus and echidna, egg-laying mammals l Marsupials – pouched mammals l Eutherians – placental mammals

Mammal Heart

Echidna

Marsupials and Eutherian

Evolution of Primates l Evolved in late Cretaceous period l Arboreal – tree dwelling l Limber shoulder joints allows to brachiate – swing from limb to limb l Prosimians – lemurs, tarsiers l Anthropoids – Monkeys, humans, apes