Characteristics of class Aves

Essay to memorize, to present, and also helpful for science students.

1. Birds

2. TABLE OF CONTENT Classification Distribution and habitat Special features of birds Characteristics of class A ves

3. CLASSIFICATION

4. DISTRIBUTION AND HABITAT With more than 9000 species distributed over the entire earth. Birds are found in deserts and forests. In mountains and prairies and on all ocean. Some birds live in darkness in caves, finding their way by echolocation , and other dive to depths greater than 45m to finding prey in aquatic life.

5. SPECIAL FEATURE OF BIRDS The unique feature of birds that distinguishes them from other animals is the feather . If an animal has feather, it is a bird and if it lacks feather, it is not a bird. No other group of vertebrate bears such easily recognizable identification tag.

6. In addition to feathers, all birds have forelimbs modified into wings (Althrough they may not be used for flight). All have hind limbs adapted for walking, swimming or perching. All have beak. All lay eggs.

7. CHARACTERISTICS OF CLASS AVES Body usually spindle shaped, with four division: head, neck, trunk, tail . Neck disproportionately long for balancing and food gathering. Limbs paired with the forelimbs usually modified for flying . Foot with four toes (2 or 3 toes in some). Epidermal covers with feathers and leg scales .

8. 5. Thin integuments are present on epidermis and dermis. 6. No sweet glands. 7. No oil gland at the base of the tail. 8. Pinna of ear rudimentary . 9. Fully ossified skeleton with air cavities. 10. Skull bone fused with one occipital condyle . 11. Tail nor elongate . 12. Sternum well developed with kneel or reduced with no kneel.

9. 13. Nervous system well developed with brain and 12 pairs of cranial nerves . 14. Circulatory system is also well developed with four chambered heart , with the right aortic arch persisting as the dorsal aorta . Reduced renal portal system. 15. Nucleated red blood cells. 16. Endothermic 17. Respiration by slightly expansible lungs , with thin air sac among the visceral organs and skeleton . 18. Syrinx (voice box) present near the junction of trachea and bronchi .

10. 19. Excretory system is developed with metanephric kidney ; ureters open into cloaca . Semisolid urine . 20. Main nitrogenous waste is uric acid . 21. No bladder . 22. Sexes separate; tests paired, with the vas deferens opening into the cloaca . Female with left ovary and oviduct only . 23. Copulatory organ is present in ducks, geese and a few others. 24. Fertilization is internal. 25. Amniotic egg (egg that contain an amnion) with much yolk and hard shell (calcareous shell). Incubation external .