1. 1 Unit 9.2 Class Aves

2. Class Aves Feathers No teeth Flexible long neck Scales on legs Bones with air spaces Endothermic Four chambered heart Amniotic egg Highly sexually dimorphic 2

3. Class Aves Sexual selection –Birds have evolved disadvantageous traits in terms of natural selection –Instead, these traits are solely for enhancing sexual attraction in potential mates The only dinosaur clade to have survived the KT extinction 3

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6. Archaeopteryx 6 Transitional animal 147 mya Reptile characteristics –Teeth –Boney tail –Fingers with claws Bird characteristics –Feathers –Enlarged sternum

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8. Adaptations for Flight Bones Air cavities reduce the weight of the bone without sacrificing strength along the axis of the bone The bone is much more susceptible to pressure from the side 8

9. Adaptations for Flight Skeletal structure Enlarged sternum –Flight muscle attachment (breast) Long neck –Counter-balance against the beating of wings during flight Elongated carpals & metacarpals –Lengthens wing span 9

10. Adaptations for Flight Wing The wing shape is known in engineering as an airfoil design Air moving above the wing moves faster causing the molecules spread out more than the air below This creates pressure below the wing and the result is aerodynamic lift 10

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12. Adaptations for Flight Feathers Light weight & strong Branches coming off the central shaft are called barbs Barbs are connected across the feather by smaller branches called barbules which hook into one another Birds have different feathers for different functions 12

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15. 15 Tail & Flight – Support during flight Semiplume – Provides shape & color Filoplume – Connected to nerve endings Bristle – Around the eyes & mouth Downy - Insulation

16. 16 Adaptations for Flight Body weight is further reduced by reducing or losing certain structures and organs –No teeth –No urinary bladder –No penis –Only one ovary –Reduced large intestines

17. Adaptations for Flight Highly efficient lungs able to remove 31% of oxygen from each breath vs. 24% in humans Needed to sustain muscles during flight Anterior & posterior air sacks store air during each breath During inhalation and exhalation, fresh air is passed across the lungs 17

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22. 22 Digestive System Crop –Storage Proventriculus –Enzymes Gizzard –Grind food Cloaca –Waste –Reproduction

23. 23 Vision Up to 8 times keener than human vision Each eye moves indendtantly

24. 24 Chicks Altricial –No feathers –Cannot walk or see –Cannot feed themselves Precocial –Down feathers –Can walk and see –Can feed themselves