Written by Saturday, 01 July 2017 23:29
In the birds vertebral column compound structure is present. It is called Synsacrum. It is formed by the fusion of 14 to 16 vertebrae. Those vertebrae are one last thorasic vertebra, Six lumbar vertebrae, two sacral vertebrae and seven candal vertebrae. This structure supports llia of the pelvic girdle.

The lumbar vertebrae will show well developed transverse pro­cess. Their neural spines are fused to form a crest.

The centrum of the sacral vertebrae are fused together and their transverse processes are also united to form bony plates. It will give support to the llia.
The last part of the synsacrum is formed by the union of first seven caudal vertebrae. Thecentrum of these vertebrae are laterally compressed. Their transverse processes are divided into dorsal and ventral portions. The dorsal portions of these vertebrae will fuse to form bony plates. The ventral portion is rod like. It is considered as a rib.

All the vertebrae of Synsacrum are completely fused and it is difficult to identify them separately.


Written by Saturday, 01 July 2017 19:50
The body wall of birds has three regions, Skin, Muscles and Perito­neum.
  1. The skin is dry. It shows upper stratum corneum, which has flat cornified cells. The feathers cover the body. Dermis shows musculo-fibrous tissue. The muscles help to raise and lower the feathers. It is supplied with blood vessels and nerve fibres.
  2. Glands are absent in the skin of a bird except preen gland which is located on the upper surface of the tail. Its secretions keep the feathers water proof.
  3. Muscles: Below the skin Muscles are present. In birds skeletal muscles are well developed. The flight muscles are well developed which help to raise and lower the wing.
  4. Peritoneum: A thin epithelium called peritoneum will cover the inner surface of the muscles.
  5. In birds skin sweat glands are absent and hence bird cools itself in hot environment by panting.


Written by Saturday, 01 July 2017 17:28
Based on characters of  Aves Class is divided into 2 sub-classes.

Sub class: i) Archeornithes and Subclass ii) Neornithes
1. Sub class Archeornithes:
  1. In this subclass extinct birds are included. Those birds were alive in Mesozoic era.
  2. These show a long tail with 13 or more than 13 caudal vertebrae.
  3. Pygostyle is absent.
  4. Meta carpals are free. The free fingers of fore limb will end with claws.
  5. Thecodont teeth are seen.
Archeopteryxfossil thumb10
Eg: Archeopteryx, Archeormis
2. Sub class Neornithes:
  1. This subclass includes both extant and extinct birds.
  2. Tail ends in pygostyle. The rectrices are arranged r a semi circular around pygostyle.
  3. Teeth are absent in many forms.
  4. Sternum is well developed. It shows a keel to which flight muscles are attached.

This subclass is divided into 4 super orders.
  1. Odontognathae
  2. Palaeognathe
  3. Impennae
  4. Neognathae
1. Super Order: Palaeognathae:
  1. These are flightless birds.
  2. They are more in numbers.
  3. Wings are reduced or absent.
  4. Teeth are absent.
  5. Caudal vertebrae are free.

This super order is divisible into 7 orders.

1. Order: Struthioni:
Ex: Struthio camelus (Two toed African Ostrich (or) Ostrich)
  1. Large flight-less bird.
  2. Feathers are less.
  3. They show two toed hind limbs.
  4. Sternum is without keel.
  5. Neck is very long and flexible.
  6. Pygostyle is absent.
  7. These birds are good runners.
StruthioAfricanOstrich thumb10

2. Order: Rheiforms:
Rhea americana. (three toed (or) American ostrich).
  1. This includes flightless, terrestrial bird.
  2. They are good runners.
  3. Wings are better developed.
  4. The body shows more feathers.
  5. The hind limb bear three toes.
  6. Sternum is without keel.
Rheaamericanaostrich thumb15

3. Order: Casuariformes:
Ex: Casuarius (Casso waries), Dromaeus (Emu)
  1. These are flightless terrestrial birds.
  2. Head shows few feathers.
  3. Neck and body show more feathers.
  4. Wings are Rudimentus.
  5. The hind limb shows three toes.
Casuariusemu thumb11
4. Order: Aepyomithiformes:

Ex: Aepyornis.
  1. These are extinct elephant birds.
  2. Wings are vestigeal.
  3. Legs are powerful.
  4. Hind limbs show 4 toes.
  5. Sternum is broad.
  6. Keel is absent.
  7. Eggs are very big.
5. Order: Dinomithiformes:
Ex: Dinornis (Extinct Moas)
  1. These are gaint flightless extinct birds.
  2. Wings are absent.
  3. Eggs are massive.
  4. Sternum is reduced without keel.
  5. Pectoral girdle is absent.
6. Order: Apternygiformes:
Ex: Apteryx (Kiwi), Newzealand bird
  1. These are flightless, terrestrial birds.
  2. Wings are rudimentary.
  3. Eyes are small.
  4. Neck and legs ve small.
  5. Hind limbs bear 4 toes.
  6. These are Nocturnal. They feed on insects.
  7. Eggs are largest relatively.
  8. These are present only in Newzeland and Australia.
7. Order: Tinamiformes:

Ex: Tinamus.
  1. These are small, terrestrial with little power of flight.
  2. Wings are short and round.
  3. Pygostyle is reduced.
  4. Eggs are big.
  5. They eat plant products.
2. Super Order: Impennae:

This super order includes flightless aquatic birds.
  1. Their foreKmbs are modified into paddles.
This super order includes only one order.
1. Order: Sphenisci formes (SPHENISCI FORMES):
Ex: Aptenodyts (Penguin)
  1. These are flightless aquatic birds.
  2. Feathers are small scale like. They cover the. entire body.
  3. Forelimbs are modified into paddles. They are useful for swimming
  4. Limbs are 4 toes.
  5. Below the skin thick layer of fat will be present.
AptenodytsPenguin thumb17

3. Super Order: Neognathae:
  1. This sub order includes modern flying birds.
  2. Teeth are absent.
  3. Wings are well developed.
  4. Sternum shows keel.
  5. Flight muscles are well devebped.
  6. Pygostyle is present.
This super order is divisible into the following orders.
1. Order: Gaviformea

Ex: Gavia immer (Common loon)
  1. These birds show powerful fight
  2. Toes are webbed.
2. Order: Podlcipit formes:
Ex: Podiceps.
  1. These are fresh water birds.
  2. Feet are lobed.

3. Order: Procellariiformes:

Ex: Puffinus (Petrels, Diomedia ) ( Wandering albatross)
  1. Skull shows large nasal gland.
  2. Feathers are compact.
  3. Wings are long and narrow.
4. Order: Pelecaniformee:

Ex: Pelecanus (Pelecan)
  1. Aquatic fish eating birds.
  2. Four toes are webbed.
5. Order: Clconiformee:

Ex: Ardea (great blue heron)
  1. Neck is long and Legs are long
  2. Web is absent.
6. Order: Ariseriformea:
Ex: Anser domesticus (Duck), Cygnus (swan)
  1. Beak is broad.
  2. Tongue is fleshy.
  3. Legs are short.
  4. Feet are webbed.
7. Order: Faiconl forme:
Ex: Mihms migrans (Kite). Pseudogyps (Vulture)
  1. Beak is short and curved.
  2. Feet show curved daws.
  3. They are strong fleers.
kite thumb19
8. Order: Galliforroea:
Ex: GaOus (Jungle Fowl), Pavo cristatus (Peacock)
  1. Beak is short.
  2. Terrestrial birds.
  3. They will fly.
9. Order: Gruiformes:
Ex: Grus (crane)
  1. They are small or medium large-size birds.
  2. They may be weak or strong fliers.
  3. Legs are long.
10. Order: Diatrymiformee:
  1. These are extinct birds.

11. Order: Chardriiforrae:
Ex: Larus (Gull)
  1. Shore dwelling aquatic birds.
  2. Toes are webbed.
12. Order: Columbiformes:

Ex: 1. Columba livia (Pigeon), 2. Sterptopelia (Dove)
  1. Skin thick and soft.
  2. Beak is usually short and slender.
  3. Crop produces pigeon milk to feed the young ones.
ColumbaliviaPigeon thumb11
13. Order: Cuculiformee:

Ex: 1. Cuculus (cuckoo), 2. Eudynamis (Koel)
  1. Many Cuckoos are parasites.
  2. The females lay their eggs in the nests of other birds.
  3. The toes are four in number.
  4. Tail is long.
14. Order: Paitiaciforme:

Ex: Psittacula eupatra (Parra keet)
  1. Feathers are green, blue, yellow.
  2. Beak is short and curved.
  3. Frugivorus forms.
15. Order: Strlgiformes:

Ex: Bubo bubo (green horned owl)
  1. Head is large and narrow.
  2. Retina contains many rods. Hence it can see in the night time.
  3. They are nocturnal predators.
16. Order: Caprimulgiformee:
Ex: Caprinulgus (Night jar)
  1. Legs are weak.
  2. Beak is small.

17. Order: Apodiformes:
Ex: Swift (Humming bird)
  1. These are small birds.
  2. They are powerful fliers.
18. Order: Coliifbrmee:
Ex: Cobus (Mouse bird)
  1. Small birds.
  2. Tail is long.
19. Order: Coraci formes:
Ex : Akedo king fisher and hornbill
  1. Beak is strong. It is useful to catch fishes.
  2. Third and Fourth toes are fused at the base.
20. Order: Piciforme:

Ex: Brachypternus (Wood pecker), Dinopium (Wood pecker)
  1. Tail feathers are pointed.
  2. Beak is stout.
21. Order: Passed formes:
Ex: 1 Passer domesticus (Sparrow), Corvus (Crow), Acridotherus (Myna)


Written by Saturday, 01 July 2017 16:57
Birds (AVES) are highly evolved vertebrates. In the Jurassic period of Mesozoic era the Birds first appeared. They evolved from Ornithischian dinosaurs of Reptilian group. In the cretaceous period the birds became modernized.
Birds are bipedal vertebrates. Their fore limbs are modified into wings. Their body is covered by feathers. Hind limbs are strong and they are useful to walk on land. All these characters taking into the consideration in classification of birds.
Birds are adopted for aerial mode of life. Hence the body shows many modifications for aerial mode of life:
The science which deals with birds is called Ornithology. (Also read Branches of Biology)
Birds and reptiles are grouped together in “sauropsida” group.

In the present day world 8590 species of birds are living.


Aves belongs to
  • Phylum: Chordate
  • Sub Phylum: Vertebrate
  • Group: Gnathostomata
  • Class: Aves
Birds arose in the Jurassic period of mesozoic era. Reptiles and Birds are combindly called “Sauropsida”. Birds have become highly, modified due to aerial life and show many differences from Reptiles. The present day living birds are represented by 8,590 species. They are aerial, terrestrial and aquatic.
birds aves types thumb24
  1. Birds are warm blooded, bipedal, feather clawed vertebrates.
  2. Birds body is divisible into head, neck, Trunk and Tail.
  3. In Birds Forelimbs are modified into wings (forelimb bears three cIaw less digits wings bear feathers. They are useful for flying.
  4. In Birds Hind limbs are strong and are useful to walk. They show 4 toes (Neognathae).
  5. In Birds the wings have no glands, except preen glands or oil gland present at the base tail. It secrets of the oily substance which keeps the feather waterproof.
  6. In Birds Skull is monocondylic.
  7. In Birds the lower jaw is made by 5 to 6 bones.
  8. The modern birds have no teeth.
  9. In Birds bones are spongy and pneumatic. They are light In weight end strong. They are use full for flying.
  10. In Birds Posterior caudal vertebrae will united arm a pygostyle. It acts as a rudder. During the flying it helps to change the direction of movement.
  11. Sternum is broad. It shows a keel. This keel is useful for the attachment of muscles.
  12. The clavicle and inter clavicle unite to form V shaped furcula. This will keep the wings away.
  13. In the forelimbs carpals and metacrpals are united to form carpo-metacarpus. Like that — hind limbs tarsal and metatatarsals, united to form Tarso metatarsus.
  14. The birds digestive system is well developed crop chamber is present. It stores food. Stomach is divided into glandular proventriculus and muscular gizzard
  15. In birds Anus is absent. Cloaca present. This cloaca is 3 chambered.
  16. In birds Respiratory system is well developed. The lungs are spongy.
    They are non distensible sacs around the lungs. Nine air sacs are present. They are usefull for make body light.
    a) lnterr cavicular air sac (1)
    b) 1 pair of cervical (2)
    c) 1 pair of anterior thoracic air sacs (2)
    d) pair of posterior thoracic air sect (2)
    e) 1 pair of abdominal air sacs. (2)
    They are useful or double respiration. They are also use Make to the body light.
  17. At the base of tracheae a syrinx is present. I has no vocal cords
  18. Birds or Aves Heart is four chambered..Right arotic arch is present.
  19. R.B.C. are oval, nucleate and biconcave.
  20. In birds (aves) Renal parallel system is reduced, or vestigial.
  21. Birds Kidneys are meta nephrlc. Each kidney is Three lobed. Ureters open into cloaca. Urinary bladder is absent.
  22. Birds Eyes are well developed. Monocular vision. In the eye comb plate or pecten is present. It protects the retina from sunlight. It also increases the vision.
  23. Birds Brain is well developed. Cerebral hemispheres and cerebellum are,12 pairs of cranial nerves are present.
  24. Sexes are separate - Sexual dimorphism is clearly exhibited.
  25. In the female left ovary and left oviduct are
  26. Fertilizing is internal.
  27. Birds are oviparous. They lay big sized eggs.
  28. During Embryo development extra embryonic membranes
  29. 13 vertebrae in pelvic region unite to form synsacrum.


Written by Saturday, 01 July 2017 01:40
In Reptiles the “organs of Jacobson” are well developed sac like chambers. They lie below the nasal cavity and above the buccal cavity. Each organ is a blind pocket. It is lined with olfactory epithelium. Each sac opens into the buccal cavity through narrow duct.
The Jacobsons organs will develop as an outgrowth from the nasal cavity. The Jacobson’s organ get nerves from the oactory nerve and a branch from the trigeminal nerve. These organs test the smell of the food when it is taken into the buccal cavity.


Written by Saturday, 01 July 2017 01:22
The trunk of chelonia is enclosed by Shell which has two parts, a dorsal carapace and a flat ventral plastron, joined on the sides. This is called tortoise shell.
It includes a median serieiof 8 small neural plates. On their right and left lateral sides 8 costal plates are present. On the margins of small 1.1 marginal plates are present. The neural plates are fused with the neural spines of 2nd to 9th trunk vertebrae. The costal plates are fused with ribs of the 2nd to 9th trunk vertebrae. At the anterior end a nuchal plate present and at the hind end a pygal plate is present.
It includes median entoplastron which êorresponds to the interclavicle and a four paired plates known as 1) epiplastra which lie in front of the entoplastron 2) hypoplastron 3) hyoplastra and 4) xiphiplasfronananged below the endoplastron serially.
This shell covers and protects the body of a chelonian. When the animal is disturbed the entire animal withdraws into the shell.


Written by Saturday, 01 July 2017 00:18
Snakes consisting Poison Apparatus by the contraction of digastric muscles in Poison Apparatus in snake the mouth is opened. Then the lower jaw moves forward. The sphenopterygoid muscles contract which results in the forward movement of pterygoid which brings rotation of maxilla, results the fang is raised and becomes directed forward.
poison apparatus snakes thumb20
The contraction of the digastric muscle will squeeze of poison gland. This makes the poison to come out of the poison gland and flows into the enemies body.


Written by Friday, 30 June 2017 23:55
It has a pair of poison glands, or ducts and a pair of fangs. The poison glands are present on the upper jaw. The poison glands are the superior labial glands. Each poison gland is sac like. It gives a duct. The duct passes along the side of the upper jaw. It opens into the groove of the fang. Fangs are of two types.

1) Open type (Ex: Cobra), 2) Closed type (Ex: Viper)

In open type the poison groove is present in cased type the Poison groove forms a canal with two openings at both ends.
poison apparatus snakes thumb20
Muscles associated with poison apparatus:
Three types of muscles are present.
  1. Digastric,
  2. Spheno-pterygoid,
  3. anterior and posterior temporalis.
snake poisonous appartus muscles thumb26
Digastric muscle is attached to the squamosal of the skull and articulates with the lower jaw. Sphenopterygoid is attached to the sphenoidal region and to the dorsal surface of the pterygoid. Anterior and posterior temporalis muscles are attached to the side walls of the cranium and the lower jaw.


Written by Friday, 30 June 2017 21:58
Based on characters Reptiles is divided into Four sub class
1. Sub-class: Anapsida:
  1. The skull of Reptiles are made by solid roof.
  2. In these Reptiles temporal vacuities are absent in the skull.
  3. In these Reptiles the quadrate is articulated with Otic bone.
  4. Limbs are strong.
  • Carapace and plastron will form the body covering.
This subclass is divided into two orders.
  1. Cotylosauria
  2. Chelonia
Order: Cotylosauria:
  1. These Reptiles are extinct.
  2. They show complete cranial roof.
  3. Pelvic girdle is flat.
  4. In these Reptiles Jaws and teeth are poorly developed.
These Reptiles resemble with Labyrinthodont Amphibians.

They became extinct in the triassic period of Mesozoic era.
Ex: Seymauria and Lepidosaurus.
Seymauria Lepidosaurus thumb12
Order: Chelonia:
This order includes Turtles and Tortoises.
Chelone turtle thumb13
  1. These are Terrestrial or aquatic.
  2. Body is covered by shell containing dorsal carapace and ventral plastron.
  3. Neck, limbs and tail are covered with scales.
  4. They show 4 limbs. pentadactyle are, modified into paddles in aquatic forms.
  5. Jaws without teeth.
  6. Jaws show horny sheaths.
  7. Quadrate is immovably articulate.
  8. Nasal opening is single.
  9. Unpaired copulatory organs are present.
  10. Cloacal opening is longitudinal.
  11. These are Oviparous.

Ex: Thonyx (Soft river terrapin), Testudo (Land tortoise). Chelone (Turtle).
2. Sub-class: Parapsida:
  1. This group includes extinct forms.
  2. Those forms lived from Triasslac period to cretaceous period.
  3. Their skull shows one pair of temporal vacuities. They are supratemporal fossae.
Ex: lchthyosaurus, plesiosaurus.
3. Sub-class: Diapsida:
  1. In these Reptiles skull shows two temporal vacuities.
  2. Modification of typical diapsid condition is common among these members.
This subclass is divided into two super orders Lëpidosauria and Archosauria.
Super Order: Lepldoauiia:
  1. These are primitive reptiles.
  2. Teeth are present on the palate jaw margins. They are not present in Sockets.

This super order includes two living orders.

1) Rhynchocephalia 2) Squamata.
Order: Rhinchocephaiia:
  1. Teeth are acrodont.
  2. The skull shows two vacuities.
  3. Quadrate bone is immovable.
  4. An epipterygoid bone is present
  5. Vertebrae are Amphicoelous.
  6. Copulatory organs are absent in this order.
Ex: Sphenodon (Newzealand)
reptiles2 thumb9
Order: Squamata:
This includes Snakes & Lizards.
  1. Their body is covered by epidermal scales.
  2. Single supra temporaI vacuity is seen in lizards and temporal vacuity Is absent In snakes.
  3. Teeth are pleurodont.
  4. Usually procoelous vertebrae are present.
  5. Transverse cloacal opening is piesent.
  6. Male shows a pair of eversible copulatory organs, useful for copulation.
This is divided into two suborders.
Sub Order: Lacertilia:
  1. These are terrestrial, arboreal or burrowing forms.
  2. Limbs &re pentadactyl and are usually present.
  3. Sternum is present.
  4. Eyelids are movable.
  5. Tympanum is present.
Ex: Calotes, Chamaeleon, Draco, Varanus, Gecko.
Sub Order: Ophidia:
This sub order includes snakes.
  1. They are terrestrial or aquatic, or arboreal or burrowing forms.
  2. Temporal vacuities are absent.
  3. Limbs and limb girdles are absent.
  4. Sternum is absent.
  5. Eyelids are absent.
  6. Tympanum is absent.
  7. Tongue is bifid.
Ex: Python , Lycodon, Naja naja, Hydrophis, Viper.
chameleon reptiles thumb17
Super Order: Archosauria:

This includes advanced reptiles.
  1. Teeth are on jaw margins and are set in muscular sockets.
  2. This super order includes a single living order Crocodilia.
Order: Crocodilia:
  1. These are fresh water and predatory forms.
  2. Body is covered by an exoskeleton made by horny’ scales & scute.
  3. Teeth are thecodont.
  4. Quadrate is immovable.
  5. Vertebrae are procoelous.
  6. Spongy lungs are seen.
  7. Longitudinal cloacal opening is present.

Ex: Crocodilus, Alligator, Gavialis
Crocodilia Gavialis thumb18

4. Sub-class: Synapsida:
  1. This group includes all extinct forms.
  2. They lived from carboniferous to permen period.
  3. Their skull shows one pair ot Vacuities. These vacuities are infratemporal fossal.
Ex: Dimetrodon, Cynognathus.


Written by Friday, 30 June 2017 21:25
In the carboniferous period of palaeozoic era “Reptiles” arose from Labyrinthodont Amphibians. In the Mesozoic era “Reptiles” dominated the entire world and that era is called "GOLDEN AGE OF REPTILES".
Cotylosauria’ is considered as “stem - reptiles”. They closely resemble the Labyrinthodont amphibians. It is not easy to distinguish these two groups separately.
In the Mesozoic era giant dinosaurs dominated the earth. In the late cretaceous period of Mesozoic era they became extinct.
In the present day world nearly 5,000 known species of reptiles are living. Reptiles are poikiothennic vertebrates. They are first true land vertebrate’s. They are the first amniotic group of vertebrate animals.
The Present day reptiles are sphenodon, lizards, snakes, turtles and crocodiles.
The Reptiles origin from labyrinthodont Amphibians in the carboniferous period of Paleozoic era. Present day living Reptiles are 5,000 species. They have an endoskeleton of dry epidermal scales and in some, bony dermal plates are present.
The Reptiles flourished in the Mesozoic era. Gant Dinosaurs dominated the earth and seas. Mesozoic era is the “Golden age of Reptiies”. Most of the giant Reptiles became extinct in late cretaceous period of Mesozoic era era.
  1. Reptiles are cold blooded Vertebrates.
  2. Reptiles are terrestrial (or) aquatic animals.
  3. The body of Reptiles is covered with horny scales (or) bonyscutes.
  4. In Reptiles Skin is dry.
  5. Glands are absent in the skin of Reptiles.
  6. Four limbs are present. They are pentadactyl (having 5 fingers).
  7. Skull occipital incompletely.
  8. In Reptiles Vertebrae are gastrocentrous.
  9. In Reptiles Ribs from a true sternum.
  10. Respiration is carried on by the lungs.
  11. In Reptiles Heart is divided into two auricles and ventricle is divided into2 chambers incompletely.
  12. Right & left aortic arches are completely formed.
  13. Red blood corpuscles are nucleated in Reptiles.
  14. In Reptiles Kidneys are meta nephric. Each kidney is provided with separate ureter.
  15. In Reptiles Twelve pairs of cranial nerves are seen.
  16. Cloaca is present.
  17. Fertilization is internal. Eggs are laid on land.
  18. In Reptiles Extra embryonic membranes are present during the development of the embryo.

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