Reptiles are the ancient inhabitants of our planet. They differ in classes and types, each of which has a distinctive characteristic. This article will introduce the reader to the environment in which and how the embryo of reptiles develops.
General information
Reptiles are vertebrates that have adapted to life in terrestrial conditions. These first ground are characterized by the following features:
- Reproduction occurs by eggs and on land.
- Breathing is easy. Its mechanism is of the absorption type, that is, when the reptile breathes, the volume of the chest changes.
- The presence of horny scales or scutes on the skin.
- The skin glands of almost all reptiles are absent.
- Separation of the ventricle of the heart by partitions is complete and incomplete.
- The skeleton of reptiles and muscles were progressively developed due to an increase in their mobility: the belt of limbs strengthened and their position in relation to the body and to each other changed. The spine is divided into different departments, and the head has become more mobile.
Reptiles today are represented by the scattered remnants of reptiles that lived on the planet many thousands of years ago. Now there are six thousand species, almost three times more than amphibians.
The reptiles living now are divided into the following orders of reptiles:
- beak-headed;
- scaly;
- crocodiles;
- turtles.
The first species is represented by the only representative - hatteria, which has an external resemblance to a lizard, but its structure is distinguished by primitive features. The habitat of the hatteria is New Zealand.
Crocodiles
The following species of reptiles belong to this detachment: caiman, gavial, Nile crocodile. These reptiles of the aquatic way of life are characterized by high organization, the presence of a four-chambered heart and a septum that separates the toes of the hind legs. To monitor the prey of crocodiles help eyes raised high above the face.
Females lay eggs on the shore next to ponds, but in a high unattended place. Nests are built from closely lying materials. Gavials use sand, where they dig eggs. Crocodiles of tropical regions to build nests mix grass and fallen leaves with the ground.
The female is able to lay up to 100 eggs, which were fertilized by different partners. Masonry occurs at night, a few weeks after the mating process. The eggs are large, similar in size to ducks.
And where does the germ of reptiles develop ? This occurs in the egg, which is located in the mother's body. During masonry, an embryo is already developing in it. The female is always near the nest, protecting future offspring from predators. Three months later, small crocodiles hatch.
Turtles
This group includes turtles: red-eared, marsh and steppe. Their body is covered with a bone shell fused with vertebrae and ribs. The jaws of turtles have no teeth. Air enters the lungs in the same way as amphibians.
Before laying the turtles build nests. Water reptiles - in the sand on the banks of reservoirs, and land - on the ground, in a dug hole. About their offspring no longer show any worries.
Many species of turtles mate in April and early May. Only in the coming spring can offspring be expected . Cubs from birth are adapted to life without parents.
Reptile Units: Scaly
These include lizards:
- viviparous;
- yellow-pusik;
- iguana.
Almost all of them, except the yellowfang, have four limbs for movement and eyes protected by eyelids. The eyelids of the reptiles of this unit are mobile.
Egg laying time is May-June. The animal acquires a mink or pit of small depth and places eggs there. There are from 6 to 16 pieces. Egg large. Inside is the yolk, which contains food supplies for the embryo. In lizards, the egg shell is soft, in crocodiles and turtles - hard.
Snakes are snakes, vipers, muzzles. They are legless reptiles, while moving their body bends. The structure of reptiles is characterized by a long spine of the trunk and the absence of a chest. Snakes have one lung. The shell of the eyes is formed by fused eyelids.
Reptiles have the ability to swallow large prey. This is achieved through movably connected lower jaws. The front teeth of poisonous snakes are endowed with a channel through which the poison falls into the victim.
Snakes reproduce sexually. On this basis, they are viviparous and ovipositing. In the natural environment, reproduction is seasonal. The time of pregnancy for snakes is different. Supper families - 48 days, pythons - from 60 to 110.
Towards the end of pregnancy, snakes begin to build nests. Their locations can be small trees, felled trunks, rodent minks, anthills. Clutch consists of 3-40 eggs. They have an elongated or oval shape - it depends on the type of reptiles.
Almost all kinds of snakes do not care about their offspring. An exception is the four-lane snake, silt snake and king cobra. They guard the eggs until snakes appear.
Breeding
This happens on land. Fertilization in reptiles is internal. Their offspring is born in three ways:
- Oviposition. This is the case when the question where the germ of the reptiles develops can be answered in the egg. The natural environment for him is the genital tract of the mother. Nutrition is obtained from an egg, after the deposition of which a cub develops from the embryo.
- Live birth. It is not inherent to all reptiles, but only to individual species of sea snakes. Where does the germ of reptiles develop? It happens in the mother’s body. From it he receives everything necessary for his development.
- Incubation method. It is used to increase the number of some kind of reptile. Females will be born from turtles and crocodiles if the temperature in the incubator is above 30 ° C, and males if lower.
And where does the embryo of reptiles in some vipers and the viviparous lizard develop? Here the eggs in the mother's oviduct are very long. A cub is formed in them, which is immediately born from the mother's body or hatches from an egg after its laying.
Reptile eggs
Reptiles developed on land. Adapting to the land environment, their eggs were covered with a fibrous shell. The most primitive shell forms of eggs are modern lizards and snakes. And so that the eggs do not dry out, their development takes place in moist soil.
Dense shells perform not only a protective function. They are the first sign of adaptation of eggs for development on land. The stage of formation of larvae drops out, due to which the content of nutrients increases here. Large reptile egg.
The second stage of adaptation of eggs for survival and further development in a land environment is the isolation of the protein membrane from the walls of the oviduct. It stores the water supplies needed by the embryo. Crocodiles and turtle eggs are covered with such a shell. In them, the fibrous membrane is replaced by calcareous. Water supplies do not pass through it, and with such protection from drying out, embryos can develop under any weather conditions.