Chapter 21 Birds Class Aves Birds members of
Chapter 21 -Birds
Class Aves • Birds members of class Aves • Major characteristics of this group: – Adaptations for flight: • • • Wings Feathers Endothermy High metabolic rate Vertebral column modified for flight – Other adaptations: • Horny bill • Lack teeth
Class Aves • Striking similarities between reptiles & birds, such as: – – Single occipital condyle on the skull Single ear ossicle Low jaw structure Behavioral characteristics: nesting & care for young – – Characteristic behaviors Songs Anatomical differences Ecological niches • Birds are thought to share lineage w/ dinosaurs & crocodilians • Distinguishing btwn Orders of birds is based on:
Evolution of Flight • Oldest Birds: – Archaeopteryx-Jurassic period-150 mya • Has well developed wishbone structure • Glider capable of flapping flight over short distances – Sinornis-135 mya • Characteristics similar to modern birds: – – Shortened body & tail Sternum w/ lrg surface area for flight muscles Claws reduced Modified wings to fold while @ rest – Eoalulavis-115 mya • Had alula-wing structure
External Structure & Locomotion • Feathers provide (2) essential fxns for flight: • • Feathers also imp in courtship, incubations & waterproofing 3 types of feathers: • Why birds maintain plumage: • How birds maintain plumage: • Feather pigments deposited during feather formation produce most colors in bird’s plumage Know why birds go through the molting process • – Form flight surfaces that provide lift & aid in steering – Prevent excessive heat loss – Contour feathers-cover tail, wing, & body – Down feathers-insulating feathers – Filoplume feathers-sensory function – To rid skin & feathers of parasites – Preening – Secretion from oil glands – Anting
The Skeleton • Bird bones are lightweight yet strong • Some bones have air spaces & internal strutting to increase strength
- Slides: 7