Birds Evolution PDF

1 OUTLINE Subphylum Vertebrata – Aves (Birds) 1. Introduction 3. Evolution 5. Skeleton 2. Dinosaurs/Birds 4. Feathers 6. Flight Muscles 7. Gas Exchange 2 Aves (Birds) INTRODUCTION Subphylum: Vertebrata; Class: O...

1 OUTLINE Subphylum Vertebrata – Aves (Birds) 1. Introduction 3. Evolution 5. Skeleton 2. Dinosaurs/Birds 4. Feathers 6. Flight Muscles 7. Gas Exchange 2 Aves (Birds) INTRODUCTION Subphylum: Vertebrata; Class: Osteichthyes Subclass Archaeornithes Neornithes (Archaeoptyrex) (contains all living birds) Superorder Paleognathae Neognathae (flightless birds) (all other birds) 3 DINOSAUR and BIRD RESEMBLANCE Theropods (carnivorous) Sauropods Birds Birds arose from the same group that gave rise to Theropods 4 DINOSAUR and BIRD RESEMBLANCE Sinosauropteryx - Theropod Dinosaur: intermediate to Dromeosaurs - Still lacked “twisting” wrist which birds have and use in flight. - Had Filaments (not really feathers but something intermediate?) 145 mya Permian 5 DINOSAUR and BIRD RESEMBLANCE Theropod Dinosaur Dromeosaur 71 mya (Velociraptor) Dromeosaurs: - wrist structure that permits "hand" turning - shoulder joints that allow arm flapping - feathers? 6 DINOSAUR and BIRD RESEMBLANCE Protarchaeopteryx Theropod Dinosaur - Close Descendent of same 125 mya lineage as Dromeosaurs - Had true Feathers. 7 DINOSAUR and BIRD RESEMBLANCE Archaeopteryx “Primitive” Bird Similarities with Birds: - contour feathers covering body and differentiated "flight feathers" - wings and reduced fingers Differences with Birds: - relatively flat sternum - forelimb bones not fused - long tail 8 EVOLUTION Archaeopteryx “Primitive” Bird Two hypotheses: 1. Arboreal theory (trees down) - tree climbers that jumped between trees - selective pressures favoured increased distance and accuracy 2. Terrestrial theory (ground up) - wings evolved as traps to catch prey - further refinements assisted in horizontal jumping & balanced landing 9 EVOLUTION Caudipteryx Early “True” Bird OR Dinosaur?? Hypothesized to be descendent of same lineage that gave rise to archeopteryx. - Sternum not as flat: keel? - Short tail 10 EVOLUTION Late Cretaceous Protarchaeopteryx Caudipteryx Neognathae (all other birds) Early Triassic Paleognathae (flightless birds)  Modern Day Birds - Feathers and Flight - Skeleton and Muscles adapted for Flight - Lungs/Respiration adapted for Flight 11 FEATHERS (3 types) 1. Contour Feathers (typical body & flight feathers) - lightweight but very strong, covering and streamlining body surface - composed of: 1. hollow quill emerging from a skin follicle 2. shaft, continuation of quill that supports barbs 3. barbs arranged in parallel, spread diagonally from shaft to form vanes 4. barbules, linking adjacent barbs by overlapping hooks If barbules detach, can be easily re-hooked by preening (running beak parallel to axis of barb) 12 FEATHERS Contour Feathers and Flight: (Wing-tip slots) Alula (3 feathers on leading edge of wing) (Mid-wing slots) Primaries (on hand bones) Secondaries (on ulna/radius) Scapular (on humerus) Let’s see purpose of the Alula and Wing-tip slots 13 Shape of bird’s wing, concave lower surface. - Creates lower air pressure on top - Air wants to move high to low Fast flight, low angle of attack pressure, generating lift. Higher angle of attack = generate more lift BUT can stall because of turbulence on trailing edge of wing. Slow flight, higher angle of attack Slow flight, higher angle of attack + Alula. Alula: forces higher speed air over top of wing even if flying slow. Prevents Stalling Wing tip vortex = Resistive drag Drag higher at speed. Bird’s solution: gaps between primaries OR narrow wing tips – Reduce drag 14 Types of Bird Wings Adapted for slow flight Adapted for speed Adapted for - alula - narrow wing tip Soaring/Gliding - wing tip slots - swept back wing - Maximize secondaries - broad wing - Longer ulna/radius 15 15 FEATHERS 2. Down Feathers (insulation) - soft tufts hidden beneath contour feathers - soft because barbules lack hooks - abundance: life-style/-stage dependent - numerous on breast & abdomen of water birds - cover entire body of some juvenile birds Substance Conductivity* Copper 0.99 Glass 0.0025 Water 0.0014 Sheep wool 0.00025 Down feathers 0.00016 *unit: g cal cm-2cm-1sec-1°C-1 Still air 0.00006 16 FEATHERS 3. Filoplumes (sensory) - fine hair-like feathers with a few short barbs at end - usually not exposed above contour feathers (exceptions, see below) - numerous nerve endings at base - communicate information about position and movement of contour feathers Example of Filoplume feathers exposed above contour feathers  Modern Day Birds - Feathers and Flight - Skeleton and Muscles adapted for Flight - Lungs/Respiration adapted for Flight 17 SKELETON - bird skeletons are light but very strong - bones are pneumatized - no tissue fills the marrow cavity of long bones (e.g. wing) -spaces in bones connect with extensions of air sacs - bone walls are thinned - thin cross-struts stiffen the bone and prevent buckling 18 SKELETON Synsacrum Pelvic Girdle - many vertebrae (except in neck) fused providing rigidity (e.g. synsacrum which together with pelvic girdle supports legs) 19 SKELETON Uncinate process Trunk ribs Sternum with keel - ribs braced against each other by uncinate processes - sternum, with large keel for muscle attachment 20 FLIGHT MUSCLES - flight muscles are large to meet demands of flight - attached to keel and humerus Supracoracoideus - positioned under pectoralis and attached by tendon to upper side of humerus - contraction raises the wing Pectoralis - largest flight muscle, upon contraction pulls wing down  Modern Day Birds - Feathers and Flight - Skeleton and Muscles adapted for Flight - Lungs/Respiration adapted for Flight 21 GAS EXCHANGE - adapted to meet high metabolic demands of flight. - composed of paired lungs and interconnected air sacs - air sacs generally arranged in pairs in thorax (ant.) and abdomen (post.) - tubes from air sacs may also extend into bones (e.g. wings, pelvic girdle) - Only one side of gas exchange system shown - air sacs have no blood vessels (avascular) (1 lung with air sacs) - air sacs facilitate unidirectional air flow through lungs. 22 GAS EXCHANGE - Internal architecture of bird lung arranged into tubular network, parabronchi through which air flows in one direction, continuously. - air flow through parabronchi is undirectional - in typical lungs, air flow is bidirectional (tidal) 23 GAS EXCHANGE - turnover of air in respiratory system requires two breaths - provides a nearly continuous unidirectional flow of air Lung Anterior air sacs Posterior air sacs 24 GAS EXCHANGE First Breath Inhalation # 1 Exhalation # 1 - inhaled air passes into posterior - exhaled air from posterior air sacs air sacs and entrance to lung. passes through parabronchi of lung. 25 GAS EXCHANGE Second Breath Exhalation # 2 Inhalation # 2 - second exhalation moves posterior air - second inhalation, air passes into sac air from second inhalation posterior air sacs and entrance to lungs. through parabronchi - again, air passing through - air entering parabronchi forces some parabronchi displaces existing air air from lungs into anterior air sacs into anterior air sacs - air in anterior air sac (from first inhalation) is now released