origins revised - Where did birds come from and why is it...

Info iconThis preview shows pages 1–9. Sign up to view the full content.

View Full Document Right Arrow Icon
Where did birds come from and why is it important? It’s important for two reasons Birds are a major class Understanding where they came from gives us insights into why they are the way they are. (Example: feathers. Are they adaptations for flight or simply inherited from ancestors?) We’ll focus on Archaeopteryx, the oldest fossil bird
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Birds obviously came from reptiles Many similarities between modern birds and reptiles Skulls hinge to vertebral column in similar ways (a single condyle) Both have a single sound-transmitting bone in the middle ear Ribs in most birds and some reptiles have uncinate processes Both have scales ( notice this in lab next week! ) Pleural (lung) cavity of birds is similar to that of crocodiles & some dinosaurs Avian air sacks resemble those of turtles and chameleons In birds and some reptiles, females have two different sex chromosomes (ZY) Eyes of birds and many reptiles contain “pectin” Birds and reptiles have nucleated red blood cells Birds and reptiles lay similar eggs; young often posses “egg teeth”
Background image of page 2
But there are important differences between birds and reptiles: Birds are endothermic; reptiles are not Birds have “double circulation” (4 chambered heart vs. 3-chambered hearts in reptiles) Birds have feathers; reptiles do not* * well, at least living reptiles do not have feathers….
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The evolutionary history of reptiles Cotylosauria (“Stem reptiles”) – about 300 million years ago Mammals, turtles, snakes, lizards branched off early For birds, Thecodonts are where the action is Archosauria (“ruling reptiles)
Background image of page 4
The debate "In fact, living birds are nothing less than small, feathered, short tailed theropod dinosaurs." K. Padian and L.M. Chiappe The Origin of Birds and Their Flight Scientific American (Feb. 1998), pg. 47 versus "Nowhere has the trap (of convergent evolution) been more successful than in luring paleontologists to the dinosaurian origin of birds." A. Feduccia preface to his book The Origin & Evolution of Birds (1996), pg. viii
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
The 5 orders of Archosaurs 1. Thecodonts . Why bipedalism (weight on two feet) is a big deal for evolution of birds. Thecodonts gave rise to the 4 other orders : 2. Pterosaurs 3. Crocodilia 4. Ornithischia (“bird hipped” dinosaurs ) 5. Saurischia (“reptile hipped” dinosaurs ) 2 groups: Sauropodomorpha Theropoda
Background image of page 6
The 5 orders of Archosaurs
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Archaeopteryx Lone feather discovered in 1861. (Asymmetrical) 1861 – a skeleton found (feathers present); not well articulated.
Background image of page 8
Image of page 9
This is the end of the preview. Sign up to access the rest of the document.

This document was uploaded on 08/24/2011.

Page1 / 31

origins revised - Where did birds come from and why is it...

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online