 inter-specific interaction, the commensalism, first the contents, definition of commensalism, then remora fish and the sharks, and the tree frogs and the plants, and the commensals they may turn into parasites. So first, the commensalism. Students' commensalism is basically a type of symbiotic relationship in which two organisms they live together. In this association, one animal is getting benefit from this association while the other animal is neither getting any type of benefit nor it is being harmed. In simple words, we can say that the three major types of symbiotic association are the mutualism, there is a parasitism and the commensalism. These three types of symbiotic association live together when there are three types of associations. So in commensalism, basically, two organisms live together, there can be two organisms, they may be plants and animals, they may be two animals. So the two organisms make a kind of association in which one organism is gaining benefit. When the other animal is not getting any benefit nor it is getting any harm, there is no harm. In this way, we have those types of examples of commensalism which we can quote. The very famous example is that for remora fish. Remora fish is basically these two small fishes which are found in marine environment in large water bodies. So the behavior of remora fish is that it has a disc on its head. By virtue of these discs, they get attached with the large animals. The large animals in the oceans, like sharks, whales or other large animals, remora fish through their discs, they get attached with that animal. When that animal moves, the remora fish are also moving along with them. So it gets attached to its body and moves with it. Now when the animal feeds, definitely it is a large animal. When it will feed, then a lot of the material, the form of the scrap will disappear. Now the food that will separate from the form of the scrap will be saved from the animal. Remora fish, they will eat that food. So what will happen is that remora fish are getting protection and they are getting food. They will utilize the remaining food of the animal. The large animals in which sharks or whales are, they are not getting any type of benefit from that animal. They do not get any benefit from the remora fish, which is the example of the commensalism. Here in this diagram, you can see the large whale shark. You can see a lot of small fishes moving along with the whale shark. Normally, if you look at it, they are getting attached to the different positions of the body. They will get attached to the discs on their head. When it is moving, they will get attached to it and move along with the animal. As soon as the animal feeds, it will detach from it. And on the sides, the food that will fall will collect and start eating. So the second example of commensalism is the tree frog and the plant association. The tree frog is a very small frog that usually lives on the trees. There are different colors in which the leaf-like color can be used. So if we look at the tree frog and the plant association diagram, the tree frog is getting benefit from the plant in the form of protection. The protection form of the plant is a small frog that is protected in the leaves of the plant. So what does the plant do in the leaves? It protects itself from predators. So this way, it is insectivorous. Whenever the insect bites, it will feed on the plant. But the plant is not taking any benefit from it. So this is the second example of the commensalism. The tree frog is getting benefit. The plant is not taking any benefit from it. So here is this diagram. You can see that the tree frog is sitting on the leaf. Because it has a small size, it usually hides itself between the leaves. Sometime, the commensal may turn into a parasite. Commonly, commensals do not damage other animals. But sometimes, when environmental conditions and physiological parameters change, a commensal may turn into a parasite. This is an example of human oral cavity. It usually lives in oral cavity and does not cause any damage. But sometimes, this antameba, the specific species of antameba, it turns into a parasite and starts decaying the gums. It starts decaying the teeth of the human. So normally, the antameba that lives in oral cavity is not a parasite, it is a commensal. But when specific conditions are created, it becomes a parasite and causes damage to the host, or the second animal.