Birds
- Created by: Louis James
- Created on: 08-01-13 17:28
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Bilogical diversity - Birds
- subclass Vertebrata: clade Archosauria (Archosaurs+avian reptiles)
- birds grouped - reptiles. reptilian features = modified
- common - diapsid skull - single occipital condyle, 1 ear bone
- nucleated red blood cells
- reptile like scales - legs (homologous)
- evolution - birds - descendents, theropods
- many had feathers - not capable - flight - sexual signalling+insulation
- evolution - birds
- Deinonychus: feathered dinosaur = transitional form
- feathers - theropods - evidence, endothermy?
- maintain body temperature above ambient using metabolic heating
- animals more active hunters - higher metabolic demand - higher mitochondrial density - higher heat generated
- heat retained via insulation - maintain internaml temperature - enzyme activity
- advantages = maintenance - core internal processed - can be active - ectotherms can't+inhabit more extreme conditions
- disadvantages = energetically expensive = limiting - food scarce. higher consumption - equivalent sized ectotherms - match metabolism
- evolution - birds = Archaeopteryx = 145 mya oldest known bird
- reptilian features = teeth, long tails, clawed forelimbs
- avian features = feathers, foot structure, paired clavicle (furcula), avian pelvic girdle
- unlikely capable - powered flight. sternum+wrist articulation
- evolution - flight. hypothesis 1 = bottom up - wings - additional thrust = escaping predators/chasing prey
- hypothesis 2 = top down - flight - climbing therapods - modified insulatory feathers glide - canopy
- top down route - Archaeopteryx
- 65 mya (Cretaceous) fossilised skeletons - powered flight possible
- large, keeled sternum - Icthyornis (retained reptilian dentition - similar morphological features - modern birds)
- clade Archosauria: class Aves
- 55 mya = giant terrestrial flightless bird = Diatryma (2m)+Phorusrhacidae (3m)
- both thought - carnivores but Diatryma herbivore
- …
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