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The body wall of birds has three regions, Skin, Muscles and Peritoneum. 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…
Based on characters of Aves Class is divided into 2 sub-classes. Sub class: i) Archeornithes and Subclass ii) Neornithes 1. Sub class Archeornithes: In this subclass extinct birds are included. Those birds were alive in Mesozoic era. These show a long tail with 13 or more than 13…
AN INTRODUCTION TO AVES (BIRDS) 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…
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…
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. Carapace: It includes a median serieiof 8 small neural plates. On their right and left lateral sides 8 costal…
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…
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…
Based on characters Reptiles is divided into Four sub class ANAPSIDA PARAPSIDA DIAPSIDA SYNAPSIDA 1. Sub-class: Anapsida: The skull of Reptiles are made by solid roof. In these Reptiles temporal vacuities are absent in the skull. In these Reptiles the quadrate is articulated with Otic bone. Limbs…
AN INTRODUCTION TO REPTILES 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…
Amphibian include anurans, urodelans and apodans. In all these groups of amphibians we come across with a great deal of parental care. Amphibians show several mechanisms to protect their eggs and developing young ones because of the they lay few eggs. Parents protect the eggs and early developmental stages…
Neoteny is defined as the failure or delay of larva to metamorphose while becoming sexually mature. It is character of some amphibians. The best example is axolotl larva of Amblystoma. It is aquatic. It has gills. It develops gonads. It lays eggs and attains large size. Amblystoma on the…
Based on characters of amphibians the present day (extant) amphibians are classified Into 3 orders. Order 1. Anura - (Frogs and Toads) Order 2. Urodela - (Salamanders) Order 3. Apoda - (Limbless amphibians) Order 1. Anura This order Anura includes frogs and toads. They can live…
Amphibians are cold blooded vertebrates. In the Devonian period of palaeozoic era they were originated from fishes, in the carboniferous period, they increased their number, hence that period is called ‘Age of amphibians’. According to Romer Dipnoi fishes are the “uncles of Amphibians” According to Newman “Dipnoi and amphibians…
Amphibians are the earliest tetrapods. They were descended from fish like ancestors. They were developed in the Devonian period. They flourished during carboniferous period. It is called “Age of Amphibians”. Amphibians can lead their life on land and in water. They are cold blooded vertebrates. They show four…
On the upper and lower surfaces of the head a number of tin- branched structures are present. They are called ampullae of lorenzini. Each ampulla contains two parts. Expanded ampullary sac and A long narrow ampullary canal. The ampullary sac contains 8 to 9 chambers. They are separated…
It lies in the auditory capsule of the skull. It is useful for maintenance of equilibrium. In the fish external and middle ears are absent. Internal eats covered by cartilaginous labyrinth. A space is present between membranous and labyrinth is filled with perilymph. The membranous labyrinth shows laterally compressed…
