Birds

  • Created by: rosieevie
  • Created on: 17-01-17 16:02

Flight

Independently evolved 5/6 times:

  • Insects
  • Terasaurs
  • Birds
  • Bats
  • Hatchet fish (NOT FLYING FISH!!)
  • Humans?
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Bird Origins

Dinosauria - Ornithischians, Saurischians, Theropods

ARCHAEOPTERYX - extinct genus             

  • Typical theropod skeleton
  • Feathers on arms and tail
  • Asymmetric feathers - capable of flight but weak (small sternum, no flight muscles)
  • Probably not closs bird ancestors
  • Combo of gliding/flying

Extinct feathered dinosaurs - Sinornithosaurus, Microraptor, Anchiornis, Caudipteryx

Dinosauria taxon never went extinct - taking birds out of the taxon makes it paraphyletic (not valid) as oppsed to monophyletic 

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Feathers and Flight

Feathers evolved from scales - first as insulation then as flight

'Trees down' theory - jumping from tree to tree evolution

Properties:

  • Aerofoil (feather shape) - teardop asymmetric = bent airflow = negative pressure for flight
  • Light body - little material inside bird bones
  • High energy - endothermic
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Dinosaur Endothermy and Bird Bills

Orginally considered 'cold-blooded' but increasing endothermic evidence - larger species relying on 'bulk endothermy' (high thermal capacity)

Bird bills:

  • Filter feeding - long,flat with fringed sides sometimes with bottom half turned downwards
  • Drinking nectar - long, slender with slight downward curve
  • Eating flesh - sharp, hooked beaks 
  • Eating insects - thin, sleder beaks, woodpecks have chisel strong beaks
  • Eating fish - long, spearlike, sometimes tooth-like structures
  • Eating seeds - short, thick conical
  • Omnivores/opportunists - multi-purpose, large and curved

Bird phylogeny constant state of flux - large variation as a result of convergent evolution causing adaptive radiation (fill different ecological niches)

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