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Wednesday, September 30, 2020

Class Aves - NEET-Biology

 Class Aves

Fig: Pigeon (Columba livia domestica)

Aves is the name of the class to which birds belong in taxonomy.

Important characteristics:

  • Skin is dry without glands except the oil or preen gland at the base of the tail.
  • Many of the characters of the birds are adaptations that facilitate flight.
  • A bird's most obvious adaptations for flight are its wings & feathers.
  • The forelimbs are modified into wings. Epidermis covered with feathers.
  • The presence of feathers is the most characteristics feature of aves.
  • Fully ossified endoskeleton & the long bones are hollow with air cavities (pneumatic).
  • They are warm-blooded animals, i.e. they are able to maintain constant body temperature.
  • The excretory system included metanephric kidneys; ureters open into cloaca; no urinary bladder; uric acid main nitrogenous waste.
  • Sexes separate; females have left ovary & oviduct only; copulatory organ (penis) only in ducks, geese, paleognaths & a few others.
  • Sexes are separate. Fertilization is internal.
  • They are oviparous & development is direct. Amniotic eggs with much yolk & hard, calcareous shells; embryonic membranes are present in the egg during development.
  • Example: Corvus (crow), Columba (pigeon), Psittacula (Parrot), Struthio (Ostrich), Pavo (Peacock), Neophron (Vulture).
  • Flightless birds: Struthio camelus (African ostrich), Rhea americana (South America ostrich), Dromaius novaehollandiae (Australian emu).
Fig: Dromaius novaehollandiae 



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