 Metamorphosis, first the contents, definition of metamorphosis, instars, advantages of metamorphosis, disadvantages of metamorphosis, the hormonal control of metamorphosis, and different types of metamorphosis. So, first the definition of metamorphosis. So, students, if we look at it simply, what is metamorphosis? Meta means multiple, more. Morphosis means shapes. So, it means metamorphosis is a process in which a animal attains different shapes compared to development. What do we call this process? Metamorphosis. So, we will have its proper definition. It is the process of abrupt, abrupt means, very sharp, abrupt morphological and physiological changes from a mature state to the mature state. So, basically these are developing stages in which an animal, from egg to adult, the embryological stages have different abrupt morphological changes. So, we call them metamorphosis. Metamorphosis, basically, happens in many animals. Especially, in invertebrates, it is very common. Invertebrates are most of the insects. In insects, 80-90% of the insects undergo metamorphosis. Similarly, we have mullisex. In mullisex, we will get it in crustaceans, we will get it in nideria, we will get it in tunicates. Some fishes, they also have metamorphosis and even the amphibians. So, if we talk about vertebrates, some fishes and amphibians have metamorphosis. Whereas, most of the invertebrates undergo metamorphosis. So, in metamorphosis, an animal undergoes different stages. And in every stage, we call it in-star. So, in metamorphosis, the animal undergoes a series of morphological changes. Different morphological stages, the animal undergoes pause on. And these series of morphological stages, they are called as the in-stars. So, if we take a look at this. As we know, in metamorphosis, we study a general pattern. From egg to larvae, larvae to pupa. After pupa, it becomes adult. But if we talk about larvae, larvae itself is a small larvae. After that, it will be a little bigger. After that, it will be bigger. And in the first stage, there is also a gradual change in the larvae. So, we call every size larvae an in-star. So, there are different in-stars even in the same morphological appearance. So, every mold, when an animal goes in the next step, it is called a large larvae from small larvae. So, we call it a mold that it has crossed. It is a mold that it has completed. So, with every mold, the animal grows. So, every mold is called the in-star. Now, it is said that if we take the larvae stage of any animal, we will see a lot of in-stars in it. Similarly, if there is a nymph stage of any animal, we will also have in-stars in nymph. So, if we look at the mosquitoes, they are having four in-star larvae. There are four in-stars in it. After four in-stars, the larvae converts into pupa. Similarly, in case of butterflies, butterflies, they are having five in-stars. Butterflies have five in-stars. The larvae of the larvae is small. The first in-star will grow from the egg. After that, it will grow a little. That will be the second in-star. If it grows further, it will be the third in-star. So, from fourth, fifth, third, overall, these are in-stars. As the mold and in-stars grow, the butterfly has a total of five in-stars. After five in-stars, the larvae of the butterfly is converted into the pupa. So, what is the advantage of metamorphosis? As there are many files of invertebrates called metamorphosis, what is its advantage? The first advantage is that usually, the egg is having a limited amount of food. The egg has a little less amount of food. So, what happens then is that the animal passes through metamorphosis. Development is also happening through metamorphosis and the animal is feeding along with it. For example, the larvae is at the larvae stage. The larvae feeds, the larvae takes food from the environment. Now, it doesn't have to do with the egg food. So, from this, it is taking food and its development is also proceeding along with it. So, one benefit is that due to metamorphosis, the animal with a small amount of yolk in their egg they can complete their development. The second important benefit of metamorphosis is that it reduces the competition between adults and the juvenile stage. The larvae stage or adult stage reduces the competition of food and reduces the competition of resources. For example, the larvae of frog it eats basically the algae. The adult frogs are insectivores and they eat insects. If there is a different food or nutrition pattern, the competition between larvae and adults will not rise. So, what are the disadvantages of metamorphosis? If we look at the disadvantages of metamorphosis, one disadvantage is that during metamorphosis, the animal spends a lot of time. He spends a lot of time crossing the stages of metamorphosis whereas for adult frog, he gets a lot of time short. That's why their adult life is very short. The adult life is short whereas the larvae stage is very long. Another disadvantage of this is that if there is a food poor environment, it is possible that the larvae is not available for food. In this case, the adult's food pattern is different from the environment whereas the larvae can be shorted and can face the scarcity of food. So, the hormonal control of the metamorphosis in metamorphosis, in vertebrates, there are different hormones in vertebrates. In vertebrates, the prime group of metamorphosis are the amphibians. In amphibians, the hormone responsible for metamorphosis is the thyroid hormones. Thyroid hormones are responsible for the metamorphosis. Thyroid hormones are mainly tri-hydro-thyronins and the tetra-hydro-thyronins. They are responsible for the metamorphosis in the case of vertebrates. In the case of invertebrates, the hormone is ectdison. Ectdison hormone is responsible. So, ectdison hormone is actually released by the prothrasic glands. Prothrasic glands are released from the glands. Prothrasic hormones are basically stimulated by the prothrasicotropic hormone. Prothrasicotropic hormone stimulates it, releases ectdison hormone. Then, ectdison will start the metamorphosis. There is another hormone in the invertebrate called juvenile hormone. Juvenile hormone works with ectdison. Then, it is necessary to produce juvenile hormone along with ectdison. Juvenile hormone does not let the larvae convert to pupa. But, when the final stage comes, when larvae convert to pupa, the secretion of juvenile hormone will be closed. Because of this, ectdison hormone works alone and because of ectdison hormone it will convert to pupa. There are two types of metamorphosis. The one is the complete metamorphosis and the other one is the incomplete metamorphosis.