 Well, next topic is reproduction in amphibians. Now, the amphibians were the first vertebrates to invade the land. After the fish, the next group is amphibians. That's why these amphibians are between the fish and the reptiles. For their reproduction, water must be used. If a group of animals come on land, they can live for a short period of time. But for reproduction, they will have to move back in water. Some animals love to live in water. If there is scorching heat, they cannot tolerate that heat. So they come back in water and keep their mouth out of the surface of water. They keep out, that is, they keep hiding in the water. And they then respire within water. And they can also take air, which is oxygenated air. Now, the amphibians were the first vertebrates to invade land. Then they have not, however, become adapted to a completely terrestrial environment. They can live completely on land, but they will have to move back in water. Now, among most amphibians, fertilization is still external, just as it is among the fishes. And this frog, as you might be knowing that at the time of fertilization, when the temperature is moderated during the monsoon season, and humidity is also there, and daytime also affects them a lot. So their ovaries and testes, they develop. And eggs are made in thousands, in any female. And this also depends on whether it is for the first time it is developing or it is spawned in 5th, 6th or 7th. When the female becomes gravid completely, the male mounts onto the female, presses the belly, and ripened eggs come out of the body. And at the same time, the male sprays mint on it, and milk, that is milk, M-I-L-T, milk, or the, there is the sperms along with the secretions that is sprayed onto the eggs, and the eggs are fertilized. And after that, in the eggs, the yolk is also there. And on the basis of that yolk, there is initial development. And then from the eggs, the larvae, which are set to, to start with, they are very small, but very fast, they develop, and then it becomes a tadpole larva. And this tadpole larva is an aquatic. It cannot come out on land. So it will develop further in the water, and then it becomes a tadpole larva, as we can see in this diagram. So this is tadpole larva. These are embryos. The embryos are in the same rounded condition, only in the egg, on the gastro-lux stage. And after that, it becomes a tadpole larva. The tadpole larva is the tail, and then there are the gills. And internally, the intestine is completely rounded, it is in the form of a coil. And then there is a process, as we call it metamorphosis. This process of metamorphosis is also in an aquatic form. The tail that starts regressing, gradually decreases, and the hind limbs also start growing, the four limbs also start growing, and this also creates a rapid change. And then it develops into a stage, which is a froglet. So if we look at this stage, there are quite a few drastic changes. There is only a hind limb in it, which is very poorly grown, and has not fully developed yet. But if we look at this stage, there are four limbs and hind limbs. And then they may come on to land, but for some time, and then they will again move back in water. And then gradually, the tail is completely absorbed, and in this way, this small froglet that is formed, and then it starts feeding on the food, aquatic food, terrestrial food, insects, and then it grows to the original, or you can say the adult form. So this is the complete life cycle for the frog or the amphibian. Now the developmental period is much longer in amphibians than in fishes, although the eggs do not contain appreciably more yolk, like reptiles, or birds. There is not so much yolk as in frog eggs. But still, it is sufficient for the early development up to the toad formation, sorry, up to the, that is the larval formation, that is called larva. The amount of food that needs to be made, that is there. Now an evolutionary adaptation present for the amphibians is the presence of two periods of development, which is the larva and the adult stages. Okay. The aquatic larval stage develops rapidly, and the animal spends much time eating and growing. This is also common. This is common. It cannot go far from the pond. There is a sufficient amount of water so that they come back very quickly in pond. Because it is that there will be more adaptations to live completely on land or dry conditions. Now after reaching the sufficient size, the larval form undergoes a developmental transition called metamorphosis into the adult, that is often terrestrial form. This is the complete life cycle. These are the strategies, these are the adaptations to live successfully that is on land or in dry conditions. Completely, there are many dry conditions. That is why they move back rapidly in water, quickly in water. Over there they feel comfortable and then they grow. They reproduction in amphibians.