Convergences (independent evolution of traits) suggest that there are replays complex eyes - arthropods, mollusks, vertebrates brain - arthropods, mollusks, vertebrates swimming -- plesiosaurs, monosaurs, whales, penguins, auks, seals, otters, beavers, crocodiles, sea turtles, marine iguanas, sea snakes flight -- pterosaurs, birds, bats (insects) gliding - squirrels, phalangers, snakes, lizards, frogs limbs - ctenida, annelids, mollusks, arthropods, vertebrates, echinoderms, polychete worms (?). complex communication - fire flys, bees, crickets, ants, beetles, fogs, fish, birds, reptiles, mammals (including human speech). Warm blooded - mammals , bird/dinosaur, tuna   Major transitions among vertebrates Earliest chordates fishes -- enlarged brain, complex eyes, heart, efficient gills, suction feeding, lateral line, fins, swim bladder (lungs in lungfish), teeth, scales Amphibians -- evolution of legs from bony fins, evolution of a lung as main source for air, desiccation resistance, skin breathing Reptiles -- Amniote egg, waterproof integument, crop, internal fertilization, 3-chambered heart. Mammals -- legs under animal, jaw articulation allowing sideways movement and grinding teeth, milk, egg retention, vertical instead of lateral bending of the spine, hair, warm blooded, 4-chambered heart Birds/dinosaurs -- legs under body and bipedalism, flight, fore limbs used as wings, feathers, hollow bones, beak and loss of teeth, air sacs in bones, weight reduction, nest building, warm blooded, 4-chambered heart   Chordate Characteristics All chordates have notochords, dorsal nerve cords and pharyngeal gill slits at some time in their life. Notochord develops from mesoderm after gastrulation Notochords of many vertebrates disappear in adults   Jawless fishes (class Agnatha) 1. First vertebrates, lived during Silurian, 450 MYA 2. Extant lampreys and hagfish (slime eels)   Fish with jaws 1. Decline of Agnathans was followed by rise of three other fishes with jaws a. Placoderms - armored fish b. Chondrichthyes - sharks and rays i. replace bone with cartilage ii. possess gills, but lack swim bladders and lungs iii. have internal fertilization c. Osteichthyes - bony fishes (18,000 spp) i. Ancestral species (lobe-fins) possess gills and lungs ii. derived species (ray-fins) possess gills iii. fish were the dominant vertebrates during the Devonian, 350 MYA 2. Jaws developed from gill arches 3. Exhibit internal and external fertilization 4. Circulatory system has one pump, e.g. a 1-chambered heart Lungs in lobe-finned fish evolved from the swim bladder Amphibians &endash; Modern groups -salamanders, newts, frogs, toads 1. Evolved from lobe-finned fishes 2. Greatest diversity during Carboniferous 3. Many went extinct during Permian extinction 4. Circulatory system has 2-chambered heart, but not 2 separate systems 5. Much gas exchange occurs through skin - must live in moist environments 6. Eggs cannot survive dessication, lack outer membranes 7. Most go through larval tadpole stage and then metamorphose (lose external gills and take the adult form) into adults   Reptiles &endash; modern groups :turtles, lizards, snakes, alligators (paraphyletic) 1. First appeared in late Carboniferous 2. Diversified during Permian, dominant group, esp. dinosaurs, during Mesozoic 3. Internal fertilization, lay amniotic egg - tough membrane that protects embryo 4. Larval stage occurs inside egg, hatch as miniature adults 5. Heart has 3 to 4 separate chambers, lack skin breathing   Stem reptiles (cotylosaurs) gave rise to a. anapsids -- turtles d. diapsids - thecodonts, which gave rise to pterosaurs, crocodiles, dinosaurs, and birds e. therapsids, which gave rise to mammals Groupings are based on differences in skull openings (fenestra). For example, anapsids, turtles have none; diapsids have two (most reptiles including plesiosaurs & dinosaurs). 7. All dinosaurs went extinct at the end of the Cretaceous although there were important extinctions before then Birds (class Aves, 9,000 spp) Close relatives of dinosaurs and some consider them living dinosaurs. Early on some birds were flightless but this is likely derived. 1. Oldest fossil (Archeopteryx) from middle Jurassic, 150 MYA, a likely relative but not true bird &endash; teeth And feathers but not a large sternum 2. Endothermic (warm-blooded) and have 4-chambered heart (as do crocodiles) 3. Mammal-like lungs for gas exchange with air sacs in hollow bones 4. Designed for flight - hollow bones, feathers, reduced symmetry in internal organs, keel (enlarged sternum), large flight muscles 5. Internal fertilization and all species lay eggs and provide some parental care 6. Divided into 28 orders with passerines the largest (60%).   Mammals (4,100 spp) Three extant subclasses &endash; monotremes, marsupials, placentals 1. Oldest fossils are Triassic, but diversified after Cretaceous extinction event 2. Endothermic, four-chambered heart 3. Possess fur (whales possess fur in utero, then lose it) 4. Possess a diaphragm to increase breathing efficiency 5. Ancestral jaw bones now form bones of the middle ear, changes improve hearing and allow sideways movement of jaws for grinding 6. Eggs only laid by monotremes - platypus and echidna 7. Females provide nutrition as milk 8. Most speciose orders include rodents (1,500 spp) and bats (1,000 spp) 9. Bats have evolved flight and ecolocation 10. Twelve orders of placental (eutherian) mammals