1. Phylum
    2. 1. Classification of Animals
    2. Protozoa
    3. Porifera
    4. Coelenterata
    5. Platyhelminthes
    6. Nemathelminthes
    7. Annelida
    8. Earthworm
    9. Arthropoda
    10. Cockroach
    11. Mosquito
    12. Honey bee and Silk moth
    13. Mollusca
    14. Echinodermata
    15. Hemichordata
    16. Chordata
    17. Pisces
    18. Amphibia
    19. Frog
    20. Reptile
    21. Aves
    22. Mammalia
    23. Rabbit bone
  2. Animal Behaviour and Adaptation
    3. 24. Animal behaviour
    25. Animal adaptation
    26. Migration
  3. Developmental Biology
    4. 27. Development of Animals
    28. Development of Frog
  4. Human Biology
    5. 29. Tissues
    30. Sense organs
    31. Digestive system
    32. Circulatory system
    33. Respiratory system
    34. Nervous system
    35. Endocrine system
    36. Reproductive system
    37. Excretory system
    38. Skeletal system
    39. Basic concept of Immunology
    40. Human diseases
  5. Evolutionary Biology
    6. 41. Origin of Life
    42. Organic Evolution
    43. Theories of Evolution
    44. Evolution of Human beings
    45. Horse Evolution
Phylum
21. Aves
▢ Introduction:
❖ Ornithology: Study of birds
❖ Otology: Study of bird's eggs
❖ Phenology: Study of bird migration
❖ Origin: Birds originated towards the end of the Jurassic period of the Mesozoic era from aerial reptiles called 'Pterosaurs'.
❖ Archaeopteryx:
◉ Description: A primitive bird and a connecting link between reptiles and birds.
◉ Features:
  1. Wings, feathers, and bird-like head
  2. Each wing had three clawed digits
  3. Toothed beak
◉ Extinction: Extinct during Cretaceous period
◉ Fossil Location: Germany
▢ General Characters:
❖ Characteristics:
  1. Feathered bipeds
  2. Air-breathing vertebrates
  3. Truly flying (other than bats)
❖ Body Divisions:
  1. Head - Jaw bones prolonged into a toothless beak or bill
  2. Neck
  3. Trunk - Limbs, two pairs, forelimbs modified as wings for flying, hindlimbs large with clawed toes
  4. Tail
❖ Skin: Without glands, only Uropygial (Preen) gland at tail base
▢ Systems:
❖ Skeletal System:
◉ Exoskeleton:
◈ Components:
  1. Feathers
  2. Scales
  3. Claws
◈ Feathers:
■ Description: Made up of keratin, showing Reptilian ancestry
■ Types:
  1. Quill feathers
  2. Contour feathers
  3. Filoplume feathers
  4. Down feathers
■ Quill Feathers:
● Role: Helps in flying
● Location:
  1. Remiges - In wings
  2. Retrices - In tail
● Coverts: Feathers at the bases of wing-quills
◉ Endoskeleton:
◈ Bones: Pneumatic and hollow, no marrow
◈ Skull: Monocondylic, like reptiles
◈ Vertebrae: Heterocoelous or saddle-shaped
◈ Synsacrum: Fusion of posterior thoracic, lumbar, sacral, and anterior caudal vertebrae
◈ Pygostyle: Fusion of last tail vertebrae
◈ Keel: Sternum large, midventral keel for flight muscle attachment
◈ Uncinate Process: Ribs with posteriorly directed uncinate process
◈ Furcula: V-shaped bone formed by fusion of clavicles and interclavicle
❖ Digestive System:
◉ Oesophagus:
◈ Crop: Dilated part for feeding and storage, secretes 'pigeon milk' during breeding season
◉ Stomach:
◈ Proventriculus: Glandular part
◈ Gizzard: Muscular part
◉ Small Intestine: Has rectal caecae at the junction with the rectum
◉ Cloaca:
◈ Chambers:
  1. Anterior Coprodaeum
  2. Middle Urodaeum
  3. Posterior Proctodaeum
◉ Excretion: Uricotelic, no gall bladder in birds like pigeons
❖ Circulation:
◉ Heart: Four-chambered
◉ Systemic Arch: Only right aortic arch persists
◉ Erythrocytes: Minute, oval, nucleated
◉ Renal Portal System: Vestigial
❖ Respiration:
◉ Lungs: Compact, spongy, non-distensible, continuous with air sacs
◉ Syrinx: Sound box at junction of trachea and bronchi
❖ Reproduction:
◉ Sexes: Separate
◉ Dimorphism: Seen in some birds (e.g., Parrot, Peacock)
◉ Oviparous: Single functional ovary and oviduct (Mullerian duct)
◉ Eggs:
◈ Type:
  1. Cleidoic (calcareous shell)
  2. Macrolecithal (yolk-rich)
  3. Telolecithal (yolk distribution)
◈ Cleavage: Discoidal, Meroblastic
◈ Development: Direct
◈ Parental Care: Well marked
❖ Nervous System:
◉ Cranial Nerves: 12 pairs
◉ Eyes: Nictitating membrane, Pecten found near blindspot
❖ Muscular System:
◉ Flight Muscles:
  1. Pectoralis major
  2. Pectoralis minor
  3. Coraco-brachialis longus
  4. Coraco-brachialis brevis
  5. Tensor muscles
▢ Flightless Birds:
❖ Characteristics:
  1. Well-developed powerful legs
  2. Small head
  3. Rudimentary wings
  4. Absence of oil glands, keel, pygostyle, and syrinx
  5. Solid leg bones
❖ Examples:
◉ Ostrich:
  1. Largest living bird
  2. Polygamous (one male attends several females)
  3. Egg weighs nearly 1.5 kg, the largest egg among animals
  4. Male incubates the eggs
  5. Easily domesticated
◉ Penguin:
    ◉ Kiwi:
    1. Found in New Zealand
    2. Smallest living flightless bird
    3. Head and neck are feathered, not naked like ostriches
    4. Nostrils located near the apex of the beak
    5. Nocturnal and burrowing habits
    6. Possesses a good sense of smell unlike other birds
    7. In proportion to its size, lays the largest eggs of any animal
    8. Oil glands present (absent in all other flightless birds)
    ◉ Rhea:
    1. Inhabits the plains or pampas of South America
    2. Head and neck are feathered, not naked like African ostriches
    ◉ Tinamus:
    1. Endemic genus of flightless birds found in the Neotropical region (South America)
    2. Located in 'Bird continent'
    ◉ Emu:
      ▢ BirdMigration:
      ❖ Instinct:
      ◉ Definition: An innate, typically fixed pattern of behaviour in animals in response to certain stimuli.
      ◉ Pronunciation: /ˈɪnstɪŋ(k)t/
      ❖ Details:
      1. Power of young birds to return to the original ground of their parents shows instinct.
      2. Migration is initiated by photoperiod, i.e., the daylight affecting the endocrine glands.
      3. During migration, birds determine compass direction using celestial bodies (sun during the day and stars at night).
      ▢ Quotes:
        ◉ Author: Huxley
        ◉ Quote: Birds are glorified reptiles.
        ◉ Author: Young
        ◉ Quote: Birds are masters of the air.
      ▢ Some birds:
      ❖ Crow:
      1. The most familiar bird of Indian towns and villages.
      2. The Koel commonly lays its eggs in nests of crows.
      ❖ Sparrow/ House sparrow:
      1. The most common bird, freely moving and nesting in the houses.
      2. Beak is conical and eyes small.
      3. Sparrows are omnivorous.
      ❖ Parrot/ Indian parrot/ Tota:
      1. Body is covered by grass green Plumage.
      2. The beak is short but stout, sharp edged, upper mandible is movable.
      3. Parrot shows sexual dimorphism. Male with rose pink collar and black throat.
      ❖ Peacock/ Peafowl/ 'Mor' or 'Mayur':
        ❖ Cuckoo/ Koel:
        1. Cuckoo is the bird which lays eggs in the nest of other birds.
        ❖ Bengal Vulture:
        1. A scavenger bird eating on carrion (dead animals); other scavenger birds are Hawks, Eagles, Crows, etc.
        ❖ Dodo:
        1. Dodo is a recently extinct bird from Mauritius. It became extinct during 17th century.
        ❖ Albatross:
        1. Albatross is a marine bird.
        2. It is the largest flying bird.
        ❖ Humming bird/ Sunbird:
        1. Humming bird is the smallest bird found in Cuba.
        2. Length = 3 cm and Weight = 2 g.
        3. Humming bird is a bird which can fly backwards.
        4. Humming bird is famous for sucking nectar.
        5. Beaks of humming bird are thin and pointed, adapted for sucking nectar.
        ❖ Swift:
        1. Swift is the fastest flying bird, speed 60 kmph. It is found in Japan.
        ❖ Wagtail:
        1. Wagtail is a famous migratory bird of India.
        2. It comes to India from Siberia.
        3. So builds nest outside India.
        ❖ Arctic tern:
        1. Arctic tern is a champion long distance migrant, travels a distance of 11,000 miles to reach Antarctica in winter.
        2. The longest annual migration is undertaken by Arctic tern.
        ❖ Siberian Crane:
        1. Migratory bird
        ❖ Golden plover:
        1. Migratory bird
        ❖ Hoopoe:
        1. Hoopoe on its head bears a conspicuous fan-shaped crest.
        ❖ Flamingo:
        1. Large bird with long neck and legs.
        ❖ Great Indian Bustard:
        1. An elongated bird