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Download Birds - Cowan Science
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BIRDS BIRD TAXONOMY Kingdom: Animalia Phylum: Chordata Subphylum: Craniata Infraphylum: Vertebrata Class: Aves Ornithology- study of birds CHARACTERISTICS OF BIRDS Adaptations for flight Appendages modified as wings Feathers Endothermic- ability to maintain constant body temperature High metabolic rate Vertebral column modified for flight Bones lightened by numerous air sacs Lay amniotic eggs Breathe with lungs Legs are covered in scales BIRDS & THEIR RELATIVES Birds are classified as “avian reptiles”…or informally called “glorified reptiles” Differences from reptiles: Have a horny bill Lack teeth Similarities with reptiles: Single occipital condyle on the skull (where the skull meets the vertebrae) Single ear ossicle Lower jaw structure Nucleated red blood cells Liver & kidney function Formation of nests for eggs BIRD & REPTILE RELATIONSHIP Birds descended from ancient archosaurs (same ancestor as dinosaurs & crocodiles) Closely related to the theropod dinosaur lineage (also shared with the Tyrannosaurus Rex and the Velociraptor) Several ancient theropods had feathers EVOLUTION OF FLIGHT Archaeopteryx- first fossil of an ancient bird Long reptilian tail and claws Short, rounded wings Feathers on the tail Lived during the Jurassic period (150 mya) Early winged reptiles used wings to either bat flying insects or trap prey against the ground Wings developed to help stabilize dinosaurs during horizontal jumps Over time, the wings evolved to allow for flight (larger flight muscles developed) DIVERSITY OF MODERN BIRDS 9,100 species 27 orders of birds Species differ based on…… 1. 2. 3. 4. Behaviors Songs Anatomical differences Ecological niches (role in the environment) EXTERNAL STRUCTURES- THE FEATHERS Plumage- covering of feathers 2 Functions of Feathers in Flight… Form the flight surfaces that provide lift and aid steering Prevent excessive heat loss Function in courtship, incubation, & waterproofing Birds of Paradise FEATHERS Feathers are modified reptilian scales that develop from tiny pits, called follicles, in the skin. Just as snakes and lizards replace their skin by molting, birds molt and replace their feathers. However, few birds shed all of their feathers at one time. FEATHERS Birds have two main types of feathers: contour feathers and down feathers. Contour feathers cover the bird’s body and give adult birds their shape. Specialized contour feathers, called flight feathers, are found on a bird’s wings and tail. These feathers help provide lift for flight. FEATHERS A contour feather has many branches called barbs. Each barb has many projections, called barbules that are equipped with microscopic hooks. These hooks link the barbs to one another, giving the feather a continuous surface and a sturdy flexible shape. FEATHERS With use, the connections of the hooks and barbs become undone. When you see a bird pulling its feathers through its beak, it is relinking these connections. This process is called preening. Most birds have a gland called a preen gland which secretes oil. When a bird preens, it spreads the oil over its feathers, cleaning and waterproofing them. FEATHERS Down feathers cover the body of young birds and are found beneath the contour feathers of adults. Their soft, fluffy structure provides good insulation for the bird, helping the bird conserve body heat. FEATHERS There are other reasons that feathers are important to birds. Their coloration may be protective (as camouflage) or may be important in the selection of a mate. The feathers of some birds allow them to blend in with their surroundings. In some species, the males develop special plumage during the breeding season. AVIAN SKELETON The bones of birds are thin and hollow. Many of the bones are fused, making a bird’s skeleton more rigid than a reptile’s. The fused sections form a sturdy frame that anchors muscles during flight. AVIAN SKELETON AND MUSCLES The power for flight (or for swimming underwater, like penguins) comes from large breast muscles that can make up to 30% of a birds body weight. These muscles stretch from the wings to the breastbone. The breastbone is greatly enlarged and bears a prominent keel for muscle attachment. Muscles also attach to the fused collarbones (wishbone). No other living vertebrates have a keeled breastbone or fused collarbones. ENDOTHERMIC METABOLISM Birds are endotherms; they generate enough heat through metabolism to maintain a high body temperature. Birds maintain body temperatures ranging from 40°C to 42°C (104°F to 108°F), which is higher than the body temperature of most mammals. These high temperatures are due to a high rate of metabolism, which satisfies the increased energy requirements of flight. AVIAN HEART STRUCTURE The ventricle of birds is completely divided by a septum. Oxygen-rich and oxygen-poor blood is kept separate, meaning that oxygen is delivered to the body cells more efficiently. The sinus venosus, which is a prominent part of the fish heart, is not a separate chamber of the heart in birds (or mammals). However, a small amount of tissue from it remains in the wall of the right atrium. This tissue is the point of origin of the heartbeat and is known as the heart’s pacemaker. AVIAN HEART STRUCTURE AVIAN LUNGS Birds use a considerable amount of energy when they fly. Since birds often fly for long periods of time, their cellular demand for energy exceeds that of even the most active mammals. To increase the efficiency of lungs, birds have air pass over the respiratory surface in one direction only. One-way air flow is possible in birds because they have air sacs connected to their lungs. There is no gas exchange in the air sacs, they act as holding tanks. AVIAN LUNGS There are two important advantages to one-way air flow. First, the lungs are exposed only to air that is almost fully oxygenated, increasing the amount of oxygen transported to the body cells. Second, the flow of blood in the lungs runs in a different direction than the flow of air does. The difference in direction increases oxygen absorption. AVIAN RESPIRATION AVIAN DIGESTIVE SYSTEM Large meals are temporarily stored in the crop, the expandable lower portion of the esophagus. The food then passes into a two-chamber stomach. In the first chamber, stomach acids begin breaking down the food. The partially digested food is then passed to the second chamber, the gizzard, where it is ground and crushed. Undigested material is eliminated through the cloaca. AVIAN EXCRETORY SYSTEM The excretory system is efficient and lightweight. It does not store waste liquids in a bladder. Instead, birds convert nitrogenous waste to uric acid, which is concentrated into a harmless white paste. The uric acid travels to the cloaca and is eliminated. EXTERNAL AVIAN STRUCTURES ADAPTATIONS OF BIRDS Type of Bird Songbirds (cardinal, robin) Beak adaptations Foot Adaptations Seed-cracking: short, thick strong beak Perching: Toes can cling to branches; one toe points backward Insect-catching: Long, slender beak for probing Hummingbirds Probing: Thin, slightly curved beak for inserting into flowers to sip nectar Hovering: Legs so small the bird cannot walk on the ground; tiny feet Woodpeckers Drilling: Strong, chisel-like beak Grasping: Feet with two toes pointing forward and two pointing backward ADAPTATIONS OF BIRDS Type of Bird Beak adaptations Foot Adaptations Parrots Cracking, Tearing: Short, stout, hooked beak used to crack seeds and nuts and to tear vegetation Climbing/Grasping: Strong toes two pointing forward, two pointing backward, adapted for perching, climbing, and holding food Birds of Prey Tearing: Curved, pointed beak Grasping: Powerful, for pulling apart prey curved talons for seizing and gripping prey
