ADAPTATION OF BIRDS FOR AERIAL LIFE

STRUCTURAL & FUNCTIONAL ADAPTATION OF BIRDS FOR AERIAL LIFE

1. STRUCTURAL AND FUNCTIONAL MODIFICATION OF AERIAL LIFE AMRUTHA K H I MSc ZOOLOGY UC COLLEGE

2. Avian fauna is described “master of air” by Young. Well a adapted to live in air Internal as well as external is modified for aerial life.

3. MORPHOLOGICAL VOLANT ADAPATAION COMPACT BODY BODY-COVERING OF FEATHERS FORELIMBS MODIFIED INTO WINGS SHORT TAIL BEAK MOBILE NECK AND HEAD BIPEDAL LOCOMOTION INTEGUMENT

4. 1.COMPACT BODY Strong dorsally and heavier ventrally ,Helps to maintain balance in the air Wings-high on the thorax Lungs, air sacs-low position Heavy muscles,sternum,digestive organs-central position

5. 2.BODY-COVERING OF FEATHERS Feathers are smooth, backwardly directed, makes the body streamlined and reduce friction Feather covering makes the body light, protects from environmental hazards and prevents loss of heat Large quill feathers on the wing and tail-used for flight Tail with a spreading fan of feathers-effective steering organ

6. 3.FORELIMBS MODIFIED INTO WINGS Forelimbs are modified into unique and powerful organ-wings These organs consist of framework of bones, muscles etc Surface area of wing is increased by development of elongated flight feathers- remiges Flight feather forms broad surface Shape of wing-thick strong edge, convex upper and concave lower surface reduces air pressure

7. 4.SHORT TAIL Tails bears a series of long, strong but light feathers or rectrices arranged in a fan-like manner Serves as a rudder for steering during flight Helps in counterbalance in perching

8. 5.BEAK Conversion of forelimb to wing is compensated by presence of bill or beak Mouth is drawn into a horny beak-used as forceps in picking-up things Also used to build nest, which in other animals is done by forelimbs.

9. 6.MOBILE NECK AND HEAD Neck is long and flexible. Birds bill is used for feeding,preening,nest building, offense and defense-mobility of neck and freedom for movement of head is very important

10. 7.BIPEDAL LOCOMOTION Hind limbs occupy anterior position on the trunk-for arboreal life Muscles are well developed and suited for perching When birds sit on the branch –toe close automatically A bird can go to sleep in this position without the fear of falling.

11. Loose skin is modified for flight It is responsible for extensive movement of skeletal musculature. 8.INTEGUMENT

12. ANATOMICAL VOLANT ADAPATAION LARGE MUSCLES OF FLIGHT PERCHING ENDOSKELTON DIGESTIVE SYSTEM AIR SACS & RESPIRATION WARM-BLOODEDNESS CIRCULATORY SYSTEM EXCRETORY SYSTEM BRAIN &SENSE ORGANS REPRODUCTIVE SYSTEM ENDOCRINE SYSTEM

13. 1.LARGE MUSCLES OF FLIGHT Control the action of wings-muscles of back is reduced ( a)Pectoralis major -largest muscle, arises from sternum & clavicle, inserted to head of the humerus.Contraction of this muscle causes downward stroke of wings-bird moves up ( b) Pectoralis minor - thinner than major,longer,contraction of this muscle causes upward stroke of the wings. (c) Coracobrachialis :small muscle that arises from sternum and coracoid,inserted on the humerus,helps to pull wing downward in flight.

14. 2.PERCHING Hind limb re suited for arboreal life. Muscles are well developed and helps in perching. Birds settles down on the tree, bend the legs and exerts a pull on flexor tendons which make them automatically to flex and grip the perch

15. 3.ENDOSKELTON Skeletal framework is stout. Bones are pnuematic,filled with air spaces, spongy Teeth are lacking, replaced by much lighter beak Vertebrae except at the neck region is fused Rigidity of dorsal part-due to fusion of vertebrae Heterocoelus vertebrae provided great flexibility and birds can freely move their neck Caudal vertebrae-formation of pygostyle-by the fusion of last 4 or more tail vertebrae

16. Presence of single occipital condoyle -head can turn freely from side to side Sternum with well developed keel serves for the attachment of flight muscles Clavicle fuse to form V shaped furcula -acts as a spring and keeps the wings well apart

17. 4. DIGESTIVE SYSTEM Rate of metabolism is high, food requirement is great, rapid digestion Selected food has high calorific value, largely utilized, minimum indigestible waste Digestive system is compact & effective Rapid elimination of undigested food-short rectum –never stores undigested food

18. 5.AIR SACS & RESPIRATION Inelastic lungs-supplemented by remarkable system of air sacs Air sacs –perfect aeration of lungs, helps in internal perspiration, thus regulate body temperature Avian lungs are completely emptied with each breath While flying movement of wings contribute to respiration-compressing &dilating the air sacs, hence birds breath more easily during flight than at other times

19. 6.WARM-BLOODEDNESS Perfect aeration of blood at high temperature(40-46),does not change with change in environment( homeothermy ) High &constant body temperature allows birds to fly at high altitudes Also facilitates activeness in every season

20. 7.CIRCULATORY SYSTEM Rapid metabolism-large oxygen supply to tissues Avian heart is 4 chambered, large sized, powerful and efficient Double circulation-oxygenated and deoxygenated blood remains separated. Hb content of avian erythrocytes is very high-responsible fro blood’s quick and perfect oxygenation.

21. 8.EXCRETORY SYSTEM Uriniferous tubules are provide with henel’s loop-efficient water absorption Coprodaeum of cloaca –efficient in water absorption Urinary bladder is absent Semi-solid waste is immediately excreted out Nitrogenous waste are excreted as uric acid crystals-important physiological volant adaptation

22. 9.BRAIN & SENSE ORGANS Brain is highly developed center for equillibrium,muscular co-ordination &instinct Cerebrum &cerebellum are highly developed Eye is remarkable for development-adapted to see very small animals from great heights Peculiar vision is due to a curious structure, comb-like pecten

23. 10.REPRODUCTIVE SYSTEM In female birds, the ovary &oviduct is of one side(left side) of the body alone . This reduces the weight of the body.

24. 11.ENDOCRINE SYSTEM Well developed endocrine system Glands such as, thyroid-neck, pitutary -brain- Iselts of langerhnas-pancreas, adrenal-kidney and endocrinal tissues are well represented Song and coloration is controlled by hormones from gonads