Class – Aves NEET Special

Class – Aves

Birds are originated at the end of Jurassic period  of Mesozoa era & modernisation in cretaceaous

Study of birds is known as "Ornithology"

Dr. Salim Ali was the great ornithologist of India and known as "Birdman of India"

Study of bird's egg is known as Oology.

Study of bird's Nest is known as Nidology.

Birds are glorified reptiles stated by Huxley.

Arrangement of wings on the body of bird is known as Pterylosis.



Main Characters

All types of birds are included in this class.

Body is boat shaped: It is divided into head, neck, trunk and tail. Neck is long and flexible.

A cover of soft feathers (derivative of stratum corneum) is present all over the body of all the birds, that is called "plumage"

Scales are found only on hind limbs.

Skin is dry and without glands. But oil glands or Preen glands are found on tail or Urophygium. These glands secrete oil, which softens and makes greasy to the feathers.

Two pairs of limbs are present.

Forelimbs (with three digits) are modified into wings, which help in flying and in conserving heat.

Four clawed digits are found on hind limbs.

A three chambered cloaca is present in the birds.

Teeth are absent in jaws. Jaws are modified into horny beak. Beak is toothless. An epidermal horny sheath is present on beak, which is called Ramphotheca.

Spongy lungs are present for respiration. Air sacs are also found, these help in flying.

Sound producing organ at the junction of trachea and bronchi of birds is called syrinx.

Heart is four chambered.Hepatic portal system is well developed in birds, but renal portal system is ill developed. Sinus venosus is absent. Only right aortic arch persist.

R.B.Cs are nucleated.Endoskeleton is bony. These bones are hollow, in which air is filled; these bones are called pneumatic bones. These make the body light in weight and help in flying.

A single occipital condyl is found in skull i.e. birds are monocondylic.Centrum of the vertebra is heterocoelous.

Last four caudal vertebrae fuse to form pygostyle.

Sternum is large. Swollen basal-part of sternum is called "Keel" This keel offers a joint plane for flight muscles.

Keel 18 highly developed in flying birds.

Ribs of birds are bifid and uncinate processes are present in ribs.Exoskeleton is in the form of soft feathers all over the body (except hind limbs). Foramen of triosseus is found in their pectoral girdle.Two bones, clavicle and interclavicle fuse to form 'V-shaped furcula.Furcula is also known as Wish bone or Merry thought bone, which act as a spring between two girdles.Furcula is absent in flight less birds.

Kidneys metanephric (Trilobed). Ureters open into cloaca.Members of class Aves are always uricotelic,

Uric acid is a semisolid substance. Excreta of marine birds is known as guano.Most of the birds do not have urinary bladder and copula toy organ.

Brain is large, smooth, highly developed.Cerebellum is well developed for aerial mode of life.Cranial nerves are 12-pairs.

The skin around the nostrils in birds, is called "Cere".Eyes are large and well developed which are surrounded by rings made 'up of bony plates known as selerotic ossicles.Eyes are large and nictitating membrane is present in eye. Vision is unilocular.

A specific comb like structure pecten is found in the eyes of all birds execept kiwi's eyes. Pecten helps in accomodation of eye and provides nutrition to eye balls. It also controls the pressure of liquid present in eye vision and telescopic vision of birds is due to pecten.   

External ears are present but ear pinnae are absent.

Columella bone (Stapes) (one ossicle) is found in middle ear. Cochlea (not coiled) is present in internal ear.

Olfactory organs are less - developed.Birds are monodelphic i.e. only left ovary and left oviduct is functional in females. Birds are oviparous vertebrates.Birds are unisexual. Sexual dimorphism is well marked. Copulatory organ is absent in males.

Fertilization is internal.They are egg laying i.e. oviparous.Eggs are large, megalecithal, telolecithal and cteidoic. Shell is perforated. Cleavage is discoidal meroblastic.Embryonic development is direct. Embryonic membranes are present, so birds are included under group amniota.All the birds form nests. Parental care is well marked. Young one without feather is known as Nidiculous and with feather is known as Nidifugous.

Birds are warm blooded or homeothermic or endothermic animals i.e. Body temperature remains almost constant, what ever may be the temperature of atmosphere around these birds.

Class Aves is divided into 2 subclasses – Subclass

(a)    Archaeornithes, Subclass

(b)    Neornithes

Subclass - Archaeornithes


Primitive "Lizard like birds:' are included in this subclass, which belong to Jurassic period. All the members have become extinct.

Wings are ill developed, i.e. capacity of flying was very less.

Pygostyle was absent.

Keel on sternum was absent.

There were present 3 - 3 clawed digits of forelimb at the free edges of wings.

Uncinate processes on ribs were absent.

Teeth were present in the jaws of skull.

All the members of this subclass are the connecting links between reptiles and birds.

E.g.

Archaeopteryx - Lizard bird. (Extinct in Cretaceous period) Its fossil was discovered by Andreas wagner in 1861 from Bavaria (Germany).



Sub class - Neornithes

This subclass includes mostly live animals and extinct animals of post jurassic period.

Wings are well developed which are used in flying (except some birds)

Last few vertebrae fuse to form pygostyle.

Sternum is bigger and with keel.

Digits of forelimbs are fused and claws absent.

Thoracic ribs are having uncinate processes.

Except some species (which are extinct) rest all the birds are toothless.

In live members of this subclass, vertebrae are heterocoelous:

This subclass is classified under four super orders.

(i)     Super order - Odontognathac:

These extinct animals were having teeth

Pygostyle was absent.

Keel in sternum is absent e.g. Hesperornis

(ii)    Super order - Impennae

All the members of this super order are aquatic birds

Forelimbs are modified into flippers * Limbs are webbed.

Teeth are absent

Sternum without keel.

e.g.Spheniscus - Penguine - It is also called "sea bird of Antarctica".



(iii)  Super order - palaeognathae or Ratitae

 It includes large and massive birds, which are flightless in nature.These are able to run fast. Wings are reduced, rudimentary, vestigeal or absent.

Caudal vertebrae are free and pygostyle is absent.

Sternum is raft like which lacks keel.

Uncinate processes on ribs are absent.

Oil glands or preen glands absent.

Sound producing organ syrinx is absent. e.g.

Struthio - African ostrich or Camel-bird - It is the largest living bird of modern period. It is almost 8 feet in height. Polygamous, male incubate the eggs (Largest egg). In this bird urinary bladder and penis is present.



Rhea - American ostrich - It also has urinary bladder and penis.

Apteryx - Kiwi - It is National bird of New zealand. It has hair like feathers all, over its body. It is smallest' flightless bird.

Dromaeus- Emu-It is a monogamous bird in which only males look after their young ones and eggs.

Aepyornis - Elephant bird

Casuarius - Cassowary (found in new Guina)/Austrails

(iv)   Super order - Neognathae or Carinatae

This super order includes small sized flight birds of modem era. Wings are well developed.Pygostyle is presentKeel in sternum is highly developed - Its crop glands secrete pigeon milk.Uncinate processes at ribs are well marked.Oil glands or preen glands are found.Beak is toothlessSound producing syring is present.

e.g.

Pavo-cristatus - Peacock - It is the national bird of India.



Psittacula krameri - India parrot (uper jaw movable - Psittaciformes)

Columba livia - Blue rock region. Its crop gands secrete pigeon milk (columbiformes)

Streptopelia - Dove

Passer domestieus - Sparrow - It shows commensalism with man.

Corvus splendens – Crow



Molpaster - Bulbul



Cygnus - Swan - Aquatic bird having webbed limbs

Dobo bobo - Bubo or owl or III of omon"

Cuckoo - It lays it eggs in the nest of other birds

(Crow)

Anas - Duck



Phoenicopterus - Flemingo



Alcedo - King fisher



Ardea - Grey heron

Dinopium - Wood peeker - Kathphorva

Albatross - Diomedea - Marine bird with largest wings in flying birds.

Milvus - Kite (Predatory birds)

Falco - Falcon (Predatory birds)

Neophron - Vulture (Scavenger bird)     

Choriotis-nigriceps- Great Indian bustard. It is also called Gondavan. It is the state bird of Rajasthan.

Helena - Humming bird - It is also called sunbird. It feeds on nectar of flowers. It is the smallest bird. It is found in Cuba. It can fly in forward and backward both the directions. It can fly like helicoptor. Its size is about 3 to 4 cm.

Ploceous - Weaver bird (Baya)

Micropodus - Pitohiudicthous/pathua - It is the only one poisonous bird, which is found in New guinea.

Swift spine tailed - Fastest flying bird, it is found in Japan.

Poor bill - Bird which shows sleeping stage and undergoes hibernation.

Migratory birds:

Pluvianlis dominica - It is an american bird which migrates from south to north and from north south.

Scolopax eusticola - It migrates from hill area planes.

Himidyan partiges - It can fly over 6000 miles

Sterna parasisaea - Champion bird - Arctic to Antarctic and back.

Bird Sanctuary

Keveladev Ghana bird Sanctuary (largest) Bharatpur (Rajasthan)

Sultanpur (Lake) bird Sanctuary - Gurgao (Haryana)

Govind Sagar bird Sancturary - Bilaspur (Haryana Chilka lake bird Sancturary - Balagaon (Orris a)

Feathers:

There are different types of feather namely (1) Quill (flight feather) consists of (a) Remiges - feather of wings (b) Retrices - feather of tail (2) Coverts – small just like quill for filling gap on wings & tail.

(3) Contours - small feather to cover the body

(4) Filoplums - Beneath the contours (5) Down feather - Cover the body of newly hatched bird.

Review

Aves (birds): Thin dry skin convered with feathers that conserve body heat/ forelimbs modified into wings, fingers without claws, toes aimed with claws, spongy little elastic lungs have air - sacs opening into them, voice box, called syrinx, is at the bifurcation of trachea into bronchi, heart is 4- chambered, eggs amniotic, fertilization internal, no larval stage, endothermic, generate body heat by rapid metabolism, nest building, parental care/ migratory behaviour