Week 11: non-avian and avianreptiles

Reptilia characteristics

ectothermic, dry, scaly skin, amniotic egg, internal fertilization, terrestrial

reptilia

non-native reptiles (paraphyletic) - becomes monophyletic when you include birds

reptilia includes

tuataras, turtles, snakes, lizards, and crocodilians

reptilia land adaptations

tough protective skin, shelled eggs with amnion, internal fertilization, advanced respiratory mechanisms

reptile skin

tough scales (scutes) made from keratin, prevents dehydration and provides protection, ecdysis

reptile reproduction

internal fertilization, eggs laid on landa

amnion

fluid-filled sac surrounding the reptile embryo and often has leathery shell

reptile respiration

negative-pressure breathing, carrier’s constraint

carrier’s constraint

legs are to the side of the body-sideways flexing while walking - can’t fully expand ribcage while walking - leads to difficulty breathing and walking at the same time

ectothermy benefits

requires less energy, can survive in low-resource environments, resilient to temperature fluctuations

reptile circulation

reptiles and amphibians both have a 3-chambered heart

crocodilia

4 chambered heart, lung muscles attached to liver - as liver pulls down, lungs expand which allows for locomotion and respiration at the same time

anapsid amniotic skull

no temporal openings (turtles)

synapsid amniotic skull

one temporal opening (mammals)

diaosid amniotic skull

two temporal openings (crocodiles, birds, lizards)

diapsid skull advantages

decreases skull weight, increased surface for muscle attachment, and increase space for jaw muscles when mouth is closed

turtles (testudines)

very different from other reptile groups (have anapsid skull and shell) - sister group of archosaurs

plastron (turtles)

bottom of shell

carapace (turtles)

top of shell

clade aves

birds descended from dinosaur ancestor av

aves characteristics

keratinous feathers, are endothermic, 4-chambered heart, no urinary bladder

bird evolution

descended from theropod dinosaurs, remnants from reptile ancestry

remnants from reptile ancestry

amniotic egg with hard shell, skeleton similar to other dinosaurs (diapsid skull), 4- chambered heart

evolution of feathers

initially evolved in non-avian dinosaurs due to thermoregulation with insulation, courtship displays, and species recognition - DID NOT INITIALLY EVOLVE FOR FLIGHT

flight adaptation

forelimbs modified into wings, large flight muscles, hollow, ridged bones, efficient respiratory system, high metabolic rate helps maintain constant body temp (endothermic), no urinary bladder

hollow bird bones

lighten skeleton

keel

attachment of pectoral muscles and lowers center of gravity

furcular

fused clavicles that strengthen thoracic cavity

bird respiration

air sacs are connected to longs, unidirectional air flow over lungs allows for efficient gas exchange

no bladder for birds

all nitrogenous wastes released as uric acid - only store as much as can fit in the ureters