Class : Amniota - Reptilia - sub phylum - Tetrapoda

 Tetrapoda

 

The vertebrates with two pairs of limbs adapted for locomotion on land are known as tetrapods. The limbs are of pentadactyl type. The tetra-pods are identified by a cornified outer layer of skin and nasal passages communicating with mouth cavity and lungs. The super class Tetrapoda is divided into four classes namely. Amphibia, Reptilia, Aves and Mammalia.

 

 

Amniota

 

The tetrapods like reptiles, birds and mammals are referred to as amniotes. The amniotes have certain membranes associated with embryos inside the egg. It is an adaptation in terrestrial forms during development. These membranes are the amnion, chorion and allantois.

 

Class : Reptilia

 

Reptiles are represented by lizards, snakes, turtles, tortoises, alliga-tors, crocodiles and the tuatara lizard, Sphenodon punctatum.

The body is variable in shape. It is covered with an exoskeleton of horny imbricate epidermal scales. Skin glands are practically absent. The limbs are of pentadactyl type adapted for climbing, running and paddling. The en-doskeleton is well ossified. Respiration is by lungs. The heart is three cham-bered (In crocodiles it is four chambered). The functional kidney of the adult are metanephros. The Sexes are separate. Fertilization is internal. The eggs are covered with leathery shells. Reptiles have developed some form of copu-latory organ to transfer the sperms into the cloaca of the female.

 

Example : Garden lizard, Cobra, Monitor lizard, Crocodile, Turtle.

Comments

Post a Comment

Popular posts from this blog

Plasma Membrane

  Plasma Membrane   It is the outer limiting membrane of both prokaryotic and eukaryotic cells. It is an ultra thin, elastic, living membrane. Plasma membrane is a dy-namic and selective transport barrier.   Since the plasma membrane is ultra thin, it could be observed only under electron microscope. Structure of the membrane is studied by isolating the same from the cell and conducting biochemical investigations.   In 1895  Overton  suggested that the membrane is made of fatty sub-stances. Other workers later concluded that two layers of lipid were present in the cell membrane. According to a model proposed by  Danielli  and  Davson  in 1935, the  lipid bilayer  of the membrane was coated on either side with protein.   In 1960,  Robertson  using electronmicrographs proposed a  unit   membrane hypothesis . According to this hypothesis the two outer layers of  protein are about 2 nm thick and appear densely granular. They enclose a   clear central area of about 3.5 nm wide consisting of
Read more

THEORIES OF EVOLUTION : Neo-lamarckism

  THEORIES OF EVOLUTION   Neo-lamarckism   Lamarck's 'theory of inhertitance' was further studied by a group of scientists. Their ideas supporting Lamarck's opinion collectively constitute neo-Lamarckism.   The neo-Lamarckians were of the opinion that 'adaptions' are universal in nature. An adaptation happens through causal relationship of structure, function and environment. Due to changes in the environment, habits and life style of organism gets altered. Thus gradually the organism acquires new structures. The newly obtained character gradually becomes an inheritable trait. This opinion and argument is a modified form of Lamarckism. These ideas stressed direct action of environment on organisms.   Support to neo-Lamarckian concept - Experiments   1. McDougall (1938) tried to prove that learning is an acquired character that can be inherited. He did his experiments on rats.   He deviced a 'T' shaped tank. The tank had two exits. One exit was well light
Read more

History of Human anatomy

  History of Human anatomy   The term 'anatomy' is Greek in origin. It takes its root from 'ana' and 'tome' (ana-up ; tome-cutting). Thus anatomy is the science of physical structure of an animal or plant studied by dissection. The Human Anatomy provided the necessary knowledge for surgery and medicine.   The study of human anatomy dates back to 2500 BC, when the Egyptians prepared mummies. They removed internal organs of cadavers be-ing mummified. They also did surgery for wounds and broken bones. In India during 500 - 491 BC Susruta performed cataract operation. In 1 st  century AD, Celsus, a Roman physician wrote about surgical procedures.   The year 1543 AD was significant due to publication of an accurate book on Anatomy by Andreas Vesalius. In 1628 William Harvey described the functioning of heart and the movement of blood in animals. These earlier works were followed by the discovery and accurate account of each and every or-gan system and organs in human
Read more