Aves Bio 2. Class Aves Feathers No teeth Flexible long neck – One occipital condyle Scales on legs...
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Transcript of Aves Bio 2. Class Aves Feathers No teeth Flexible long neck – One occipital condyle Scales on legs...
Class Aves
• Feathers• No teeth• Flexible long neck– One occipital condyle
• Scales on legs• Bones with air spaces• Endothermic• Four chambered heart
Evolution and Classification
• Birds are Vertebrates of the Class Aves
• The evolution of warm-blooded, has enabled birds to survive in virtually every known environment
Origin and Early Evolution
• Evidence from fossils and from studies of comparative anatomy indicates that birds evolved from reptiles
• Their features and their fragile hollow bones do not preserve well.
Caudipteryx
• Feathered dinosaur• Flightless• Transitional fossil– Dinosaur arms– Dinosaur teeth
• Only front of upper jaw
– Bird feathers
Archeopteryx
• Reptile characteristics– Teeth– Boney tail– Fingers with claws
• Bird characteristics– feathers
Classification
• Most taxonomist classify the nearly 9,000 species of Class Aves into 27 orders
• To classify birds into orders and families taxonomists most often use morphological evidence from beaks, feet, plumage, bone structure, and musculature.
Endothermic
• Warm blooded
• Ability to generate heat & maintain a constant body temperature
• Can live in hot or cold climates
• Requires more food
• Requires faster body processes to generate heat
Feathers
• Uses– Flight– Insulation– Water proofing
• Homologous to scales of reptiles• Colors from– Pigments associated with epidermal cells– Striations in barbs
• Shed continuously (except Penguins)• Accelerate at different times of year (molting)
Contour Feathers
• Hollow quill• Rachis subdivided into barbs • Barbs connected by barbules• When used in flight, called
flight feathers
Powder Down
• Similar to down feathers– Tips disintegrate– Produce talc-like powder– Waterproofs animal
FeathersUsed in many ways• Flight
• Regulation of body temperature (thermoregulation)
• Protection of the body
• Attraction of mates
• Identification of species
Types of Feathers• Contour feathers
cover the body of a bird and have a strong, hollow shaft and network of hooks.
• Down feathers are small and are located under the contour feathers to insulate the bird from the cold.
Feather Anatomy
• Rachis – stiff “backbone” of feather
• Barb – branch off of rachis
• Barbule – connect barbs
• Calamus =Quill the hollow horny barrel of a birds feather.
Contour Feathers
• Flight feathers - remiges • Tail feathers - rectrices
• Act as brakes and a rudder
• Most birds have 12 tail feathers
Preening
• A bird spends part of each day making minor repairs to tears in its feathers
• Feathers are re-zipped
Down Feathers
• Soft & fluffy
• Cover the body of nestlings
• Provide an undercoat insulating adult bird
Wing Types• Elliptical– Low aspect ration (ratio of length to average width) – Greater maneuverability
• High speed– High aspect ratio– Stay aloft at low speeds
Wing Types• Dynamic soaring– High aspect ratio
• High lift– Heavy, large bodies– High lift at low speed
Skeleton• Strong yet light bones• Pneumatized space with cross
struts• Spaces extend to air sacs of
respiratory system• Birds not any lighter than other
mammals of same size– Distribution of weight over legs
provide lower center of gravity– Aerodynamic stability
Skeleton
• The sternum supports the large breast muscles
• The humerus, ulna, and radius, along with the pectoral girdle and the sternum, support the wing.
• The pygostyle, the terminal vertebra of the spine, support the tail feathers, which also play an important role.
Skeleton• Several parts fused to
increase rigidity
• Ribs brace each other in addition to attachment to vertebrae & sternum (braces are called uncinate processes)
• Clavicles fused to a furcula (pulley bone in chickens) which flexes during flight
Muscles• Pectoralis largest– Downward beat of flight
• Surpacoracoideus raises wings
• Pectoralis connects to humerus with keeled sternum.
• Surpacoracoideus connect to coracoid bone with keeled sternum
Beaks and feet
• Hawks and eagles have powerful break and clawed talons that help them capture and then rip their prey.
• Swifts have a tiny breaks that opens wide like a catcher’s mitt to share insects in midair.
• The feet of flightless birds, on the other hand are modified for walking and running
Feet
• Mostly bone, scales and skin
• Keeps bird from feeling cold and heat at foot
• Perching due to special tendons
Circulatory System
• 4 chambered heart• Closed system• Separation of respiratory and systemic circulations• Right aortic arch leads to dorsal aorta (left in
humans)• Larger the bird, slower the heartbeat
Circulatory System
• 4 chambered heart• Right and left sides completely separated• Right side receives deoxygenated blood from the
body and pumps it to the lungs• Left side receives oxygenated blood from the lungs
and pumps it to the rest of the body• Has a single aortic arch• Most birds have a rapid heart beat compared to
other vertebrates-Hummingbird-600 times a minute
Respiratory System
• Nine air sacs– Connect to lungs and
centers of bones– Cools the bird
• Fresh air always moving– No dead ends as in
mammals• Each wing beat moves
air– Never run out of air
Respiratory System
• 9 interconnecting air sacs paired in thorax and abdomen– Divide into extensions to bones
• Branches of bronchi don’t end in alveoli as in humans– Form parabronchi – Then into air sacs
Respiratory System
• When bird exhales the carbon dioxide-rich air from the lungs, oxygen rich air is forced out of the posterior air sacs into lungs via small air tubes
Feeding & Digestion• Diet
– Euryphagous (omnivores)– Stenophagous (select diet)
• Large appetites due to high metabolic requirements• No teeth• Gizzard for grinding (keratinized plates)• Proventriculus adds gastric juices• Crop stores food• Caeca – where small intestine joins cloaca
– Hold bacteria in herbivorous birds• Young birds have bursa of Fabricius
– Process B cells of immune system
Digestive System
• Crop– Storage
• Proventriculus– Enzymes
• Gizzard– Grind food
• Cloaca– Waste– Reproduction
Excretory System
• The avion excretory system is also efficient and light weight
• The two kidneys filter a nitrogenous waste called uric acid from the blood
• highly concentrated uric acid travels by ducts called ureters to the cloaca, where along with undigested matter from the intestines, it is excreted in a semisolid, usually white mass
Nervous System
• Birds have a large brains, relative to their size
• Cerebellum coordinates movement
• Cerebrum controls complex behavior patterns such as navigation, mating, and nest building
• Optic lobe receives and interpret visual stimuli
• Have good color vision
Nervous system• Birds large eyes are located near the sides of its head, giving a
bird a wide field of vision
• Birds with eyes near the front of the head have better binocular vision
• Hearing important to nocturnal species
• Birds lack internal ears-ear canal leads to a tympanic membrane, called an eardrum
• Sense of smell is poorly
Migration & Navigation
• Most have established routes• ½ of all species migrate– Most from north to south in fall and south to north in
spring• Parameters of migration– Use of different routes in fall and spring– Time to complete route– Night vs day migration (or both)– Distance of migration– Use of landmarks
Direction Finding
• Factors– Use of topographical landmarks– Flock behavior by following experienced birds– Innate sense of time– Use of earth’s magnetic field– Celestial clues (both stars and sun)• Sun-azimuth orientation (use of sun and innate sense
of time)
Migration• When temperatures drop and the
food supply dwindles, these birds migrate to warmer climates.
• Some species monitor the position of the stars or the sun.
• Others rely on topographical landmarks, such as mountains.
• Magnetic cues, changes in air pressure, and low –frequency sounds may also provide information to migrating birds.
Migration
• Sissor-tailed flycatchar• Migates to Central and
South America in October
• Returns in April
Reproduction
• Males with paired testes• Females often have only left
ovary and oviduct• Males typically have no penis
(waterfowl do)• Egg captured by oviduct
(infundibulum)• Yolk added, then shell• Sperm remains viable in some
species 5-6 days
Incubation and Development• A female bird usually lays eggs in
the nest. One or both parents will incubate or warm the eggs by sitting on them.
• The cover them with a thick, featherless patch of skin on their abdomen called a brood patch.
• In penguins the male emperor heats the egg by placing it on his webbed feet and enfolding it with his warm abdomen.
Territoriality and Courtship• During the breeding season many
male birds establish an area that they defend against other males of their species, a behavior called territoriality.
• The male then attempts to attract a female to share this territory.
Nest Building• Nests hold eggs, conceal young
birds from predators, provide shelter from the elements, and sometimes even serve to attract a mate.
Benefits of Birds to Man
• Eat insects, rodents and weeds
• Spread seeds for flowers and trees
• Food • Sport• Pets
Order Passeriformes
• Perching foot• Songbirds• 5000 species• Mocking bird• Thrushes• Swallows• Magpie • Crow• Starling• Jays
Hummingbirds
• Fly up, down, left, right, backwards and upside down
• Wings beat 50 -200 times per second
• Heart rate =600 bpm• Eat 2/3 body weight
each day• Nectar, pollen & insects
Order Psittaciformes
• Thick tongue• Hinged and movable
upper beak• Bright colors• Parrots• Parakeets