flight adaptations
DESCRIPTION
Flight Adaptation in birdsTRANSCRIPT
FLIGHT ADAPTATIONS IN
BIRDS
UMESH BHARTI
ASSISTANT PROFESSOR
GOVT. COLLEGE FOR GIRLS
SECTOR-11, CHANDIGARH
A STRUCTURE THAT COMBINES
STRENGTH AND LIGHT WEIGHT
The evolution of flight has endowedbirds with many physical features
Wings and feathers.
Fusion and elimination of somebones
“Pneumatization" (hollowing) of theremaining ones.
Some of the vertebrae and somebones of the pelvic girdle of birdsare fused into a single structure, asare some finger and leg bones.
Hollow bones are connected to therespiratory system.
To keep the cylindrical walls of abird's major wing bones frombuckling, the bones have internalstrut-like reinforcements
BASIC MECHANICS OF BIRD FLIGHT
The fundamentals ofbird flight are similar tothose of aircraft.
Lift force is produced bythe action of air flow onthe wing, which is anairfoil.
The lift force occursbecause the air has alower pressure just abovethe wing and higherpressure below.
EVOLUTION HAS CREATED IN THE AVIAN
SKELETON A MODEL OF PARSIMONY,
LIGHTENING WHERE POSSIBLE
The bird skeleton is highly
adapted for flight. It is extremely
lightweight but strong enough to
withstand the stresses of taking
off, flying, and landing.
One key adaptation is the fusing
of bones into single ossifications,
such as the pygostyle.
The bird have a deep, solid
breastbone (sternum) to which the
wing muscles can be anchored.
PRESENCE OF SUPPORTING BARS AND
AIRSPACES IN BONES OF BIRDS
Photo by: Umesh Bharti
LIGHTWEIGHT BEAKS
Birds also lack teeth or
even a true jaw, instead
having evolved a beak,
which is far more
lightweight.
The beaks of many baby
birds have a projection
called an egg tooth, which
facilitates their exit from
the amniotic egg.
EFFICIENT RESPIRATORY SYSTEM
A bird's respiratory system isproportionately larger andmuch more efficient.
An average bird devotes aboutone-fifth of its body volume toits respiratory system.
The lungs of birds are lessflexible, and relatively small,but they are interconnectedwith a system of large, thin-walled air sacs in the front(anterior) and back (posterior)portions of the body.
Air sacs are connected with theair spaces in the bones.
BIRDS LUNGS OBTAIN FRESH AIR DURING
BOTH EXHALATION AND INHALATION
Birds' lungs are anatomically very complex (theirstructure and function are only barely outlinedhere), but they create a "crosscurrentcirculation" of air and blood that provides agreater capacity for the exchange of oxygen andcarbon dioxide across the thin interveningmembranes.
A breath of inhaled air passes first into theposterior air sacs and then, on exhalation, intothe lungs. volume.
Air passes through the lungs in both exhalationand inspiration, with the air sacs functioning asa reservoir for the next breath of air.
Avian lungs do not have alveoli, but insteadcontain millions of tiny passages known asparabronchi, connected at either ends by theand .
Air flows through the honeycombed walls of theparabronchi into air vesicles, called atria, whichproject radially from the parabronchi.
These atria give rise to air capillaries, whereoxygen and carbon dioxide are traded withcross-flowing blood capillaries by diffusion.
BIRD'S CIRCULATORY SYSTEM, WELL
EQUIPPED TO HANDLE THE RIGORS OF
FLIGHT.
A bird's heart is large, powerful
It is a four-chambered structureof two pumps operating side byside.
One two-chambered pumpreceives oxygen-rich blood fromthe lungs and pumps it out to thewaiting tissues.
The other pump receives oxygen-poor blood from the tissues andpumps it into the lungs.
This segregation of the two kindsof blood makes a bird'scirculatory system, like itsrespiratory system, well equippedto handle the rigors of flight.
MUSCLE POWER
The flight muscles of most birds are red in color ("dark meat")because of the presence of many fibers containing red oxygen-carrying compounds, myoglobin and cytochrome.
They are also richly supplied with blood and are designed forsustained flight.
LOSS OF RIGHT OVARY TO REDUCE WEIGHT
FOR FLIGHT
The male have two testeswhich become hundreds oftimes larger during thebreeding season to producesperm
The female's ovaries becomelarger, although only the leftovary usually functions.However, if the left ovary isdamaged by infection orother problems, the rightovary will try to function.
SHARP EYES & LARGER BRAIN
Birds have found many ways to streamline,lighten, or totally eliminate unnecessaryparts (like urinary bladders)
Birds have brains that are proportionatelymuch larger than those of lizards andcomparable, in fact, with those of rodents.
The brain is connected to sharp eyes, andhas ample processing centers forcoordinating the information receivedfrom them.
A bird's nerves can rapidly transmitcommands of the brain to the musclesoperating the wings.
SYNSACRUM FORMS A RIGID STRUCTURE
WHICH CARRIES THE WEIGHT OF THE HIND
END OF THE ANIMAL
The synsacrum is a skeletalstructure in which the sacrumis extended by incorporationof additional fused orpartially-fused caudal orlumbar vertebrae.
The ilium of the pelvis isattached to the synsacrum.
In birds, posterior to thesynsacrum there are usuallyonly a few free caudalvertebrae, on the end ofwhich lies the pygostyle.
Photo by: Umesh Bharti
The furcula ("little fork" in Latin) is a
forked bone found in birds, formed by
the fusion of the two clavicles.
Its function is the strengthening of the
thoracic skeleton to withstand the rigors
of flight.
A keel is an extension of the sternum
(breastbone) which runs axially along the midline
of the sternum and extends outward,
perpendicular to the plane of the ribs.
The keel provides an anchor to which a bird's
wing muscles attach, thereby providing adequate
leverage for flight.
UNCINATE PROCESSES OF THE RIBS
The uncinate processes of theribs are extensions of bone thatin birds project caudally fromthe vertical segment of each rib.
These processes help tostrengthen the rib cage of birdsby overlapping with the ribbehind them
They are also shown to have arole in respiration by increasingthe effectiveness of musclesinvolved in inspiration includingthe appendicocostal muscles
Photo by: Umesh Bharti
FEATHER
Bird feathers consist of a shaft with rows offine filaments (barbs) on each side.
The barbs themselves have finer filaments(barbules) branching from them.
THREE SETS OF FEATHERS
The bird's forelimbs, the wings, are the key to bird flight. Each wing has a central vane to hit the wind,
composed of three limb bones, the humerus, ulna and radius.
The hand, or manus, which ancestrally was composed of five digits, is reduced to three digits which
serves as an anchor for the primaries, responsible for the wing's airfoil shape.
The other set of flight feathers, behind the carpal joint on the ulna, are called the secondaries.
The remaining feathers on the wing are known as coverts, of which there are three sets.
AIR PASSES BETWEEN VANES AIR
RESISTANCE CLOSES VANES
The flight feathers overlap
in a way that lets air pass
between them during the
upstroke, so reducing air
resistance.
During the downstroke
the gap is closed so
offering maximum air
resistance and giving lift.
ASSOCIATION BETWEEN MUSCLE &BONE
FRONT VIEW OF SKELETON AND WING
MUSCLES TO EXPLAIN FLAPPING FLIGHT
4 Upthrust transmitted
from wing to coracoid5 Whole body
lifted
tendon of minor pectoral
muscle
2 Wing pulled down
keel
sternum
major pectoral muscle (depresses wing)
minor pectoral muscle (raises wing)
coracoid
3 Air resistance gives
upthrust on wing
1 Major pectoral
muscle contracts
EXERCISE TO SHOW THAT BONES OF BIRDS
ARE LIGHTER
Mammalian skull Avian skull
QUICK RECAP
WHAT IS THE ROLE OF:
Keel
Pectoral muscles
Wish bone
Pecten of eye
Feathers
Synsacrum
Pneumatic bones
MOST FREQUENTLY ASKED QUESTIONS
How is a bird's body adapted for flight?
Explain morphological adaptations of flight in
birds?
Give an account of physiological adaptations for
flight shown by birds?
Write a note on flight adaptations of birds?
REFERENCES
1.Adaptations for Flight.[Internet]cited 2006-May-09, Available from: http://www.stanford.edu/group/stanfordbirds/text/essays/Adaptations.htm
2. Hasting L.Your guide to animal/wild life, Birds. [Internet] cited 2006-May-09 Available from: http://animals.about.com/od/birdsastudyguide/a/introtobirds.htm
3. Bird flight.2006-May-10[Internet]cited 2006-May-09.Available from: http://en.wikipedia.org/wiki/Bird_flight