Reptiles finalize the transfer from the water to the land. Their body is protected by a dry skin. There are over 6 100 described species so far. Reptiles are a lot different compared to amphibians. Even the egg structure is a lot different. Reptilesí egg has got three protective membranes plus a shell. This enables them to survive without any water.
Anatomy: The skeleton is almost entirely made of bones. In this group we can spot the differentiation in the cervical spine. There is an atlas and an axis (the first two cervical vertebrae), which allow these animals to move their head more freely compared to amphibians. Apart from that we can spot another change in the thorax part. Ribs are fixed to the vertebrae.
Physiology: Breathing is also on higher level compared to amphibians. The inner lung surface is more developed and differentiated. Heart consists of two atriums and one ventricle. The heartís ventricle is separated by an incomplete septum into two different parts. The right one is used for the venous blood and on the other hand the left part of the ventricle is used for the arterial blood. The pulmonal artery comes from the right part of the heartís ventricle and aorta comes from the left part. As there is an incomplete ventricular septum there comes to a mixture of an oxygenized and deoxygenized blood.
Reptiles just like amphibians belong to ectothermal animals, so their body temperature depends on their environment.
Reproduction: Reptiles lay eggs into the water. Around their embryo there is an ďamnionĒ being created. The space between embryo and the amnion is filled with amniotic fluid. Nervous system especially hemispheres in the frontal lobe are more developed compared to amphibians.
There are several groups in the Reptilia class. Chelonia (Turtles): can live in the freshwater as well as in the sea. Besides they can live terrestrial life as well. They have got a unique and a typical shelter which is mainly used for their protection.In Europe we can find Emys orbicularis, Testudo gracea and so on.
Another group is called Squamata. Their body is covered with scales (squama means a scale). Squamata include the majority of reptile species. This category can be divided into two subcategories: Lizards (Sauria) and Snakes (Ophidia). Lizards have got extremities and they can move their eye-lids. This subcategory includes species such as Lacerta agilis, Anguis fragilis etc. Snakes do not have any extremities. They do not have any pelvic area or a chest bone. Their skeleton consists of two parts: a thorax part and a tail one. Some species have sharp teeth which may contain a poison. In central Europe we can find Vipera berus ar Natrix Natrix. Crocodiles ( Loricata): are the most developed reptiles. Their heart has got two atriums and two ventricles. Moreover these two ventricles are separated by a complete septum! Teeth are located in alveolae in a jaw (specially designed teeth holes). They even use a diaphragm for breathing. This group includes Alligator, Cajman, Gavialis and crocodiles (for instance Crocodilus niloticus which can be long up to 10 metres).
Reptiles Class is a heterogeneous group of vertebrates which colonize every type of land or water. They can be found in all areas ranging from the oceans to the deserts and from mountain to Arctic.