 Well, next topic is reproduction in reptiles or reptiles is a group of animals which creep on to the surface of water, on to the surface of land or they have the scales on their bodies, they have the scales of their bodies. So, the reptiles with the first, that is the first group of a vertebrates to completely abandon the aquatic and habitat because of adaptations that permitted sex reproduction on land. So, these reptiles are the first group which is completely terrestrial, evolutionarily. The amphibians, we see that they are aquatic and terrestrial, but these reptiles have completely become terrestrial and obviously they are based on certain adaptations, but because we are looking at reproduction wise, so we will talk about reproductive-related adaptations. Now, a crucial adaptation, first found in reptiles is internal fertilization. The gametes, if the gametes they come out on land, they will dry up and they will die. So, fertilization is internal. There is a heat period, there is sex mating desire and at the same time there is egg release and at the same time male that introduces sperm into the body of the female. The egg that has not yet been shelled, it is in the developmental stage, it is only in the form of a yolk and at that time this egg is fertilized. And as it comes out of the reproductive system, from the tube, by the time the egg shell is also formed and then the egg shell is also formed. The egg membrane is also formed and the egg shell is also formed. And then at this time the egg is laid down. And the parent or the crevices go there and the egg is laid down, where there is a complete protection. Or there are some animals like turtles or tortoises. So, in the rat, the sandy shore, they bury the eggs there. Or they do not incubate the eggs. In fact, they just leave them by covering them with sand. And then all the development will be done in the egg shell. So, many reptiles and they are oviparous. They lay eggs but they are fertilized eggs. Fertilization is internal and the eggs are deposited outside the body of the female. Now, others are oviviparous. There are some reptiles like that. Fertilization development is also internal. And those young ones, they are laid, they are given birth. They form eggs and hatch in the body of the female and the young are born alive. Now, the shelled egg and a protective embryonic protection shell. Then there are membranes which we call the extra embryonic membranes. And there is an amnion in which there is an aquatic environment, in which there is complete development. So, embryonic membranes are also first seen in reptiles. This is the first time evolutionarily these reptiles are seen. Then they constitute two other important evolutionary adaptations to life on land. So, these are the shelled eggs and these are the membranes. Now, these reptiles allow reptiles to lay eggs in dry places without danger of desiccation. Because this shell is a kind of leathery type, in which there are many minimum chances of water evaporation. And therefore, the environment inside the shell is aquatic. Because for development, the aquatic environment must be. Dry conditionment development cannot be done in any condition. Now, as the embryo develops, the extra embryonic chorion and amnion help protect it. Later, by creating a fluid-filled sac for the embryo. And these are the embryonic membranes which are protective layers. Protection for which? For embryo development. The allentize permits gas exchange and stores excretely products. And this is an additional membrane which comes out of the body. It spreads under the shell like a balloon. And this is how a contact develops. Along with the shell, we call it the allentize membrane. So, that is said to be the respiratory surface where there is an exchange of gases. And the nitrogen waste also stores in it. Now, complete development can occur within the shell. In the shell itself, it is called complete development. Like we talked about in the previous module. The reptiles, the development in them is almost complete. And the shell, the gestation period of them is complete. So, the young plants, it comes out and starts running. This is how much its development is completed. Now, when the animal hatches, it has developed to the point that it can survive on its own. Or with some parental care. There is a little parental care. There is a little parental care. You cannot say that it is not at all. It is not enough for one or two days until its parental care. In this diagram, one can see the internal developmental stages. There is a lizard and a reptile. These are the eggs which have been laid down by this female. There is a lizard. And this is the egg in which the complete development has been done. Now, it has to come out of this shell. Before that, what is going on that can be seen in this diagram. This is the embryo. This is the whole of the egg. And this is the shell egg. And this is the leathery skin. This is the leathery or shell egg. This is the amnion egg which is immediately surrounding the embryo. Then there is the alentase. This is the alentase. This comes into contact with the inside of the shell. And this is the place which is an exchange of gases. And then there is the corion which surrounds the shell. And this is what is called the yolk sac. It develops the blood capillaries. It is the blood then which transports the food contained in yolk to the developing embryo. Everything is available which is necessary for the development of the young. And by the time this yolk sac is consumed, this embryo is sufficient. It has become almost independent. The shell will break. And this embryo will come out. These are the reproductive strategy in case of reptiles. So this is all about.