 Interspecific interactions coexistence. First the contents, definition of coexistence, then how coexistence occurs in nature and coexistence may turn into the competitive exclusion. So, first the coexistence. Residency to coexistence basically it is a topic related to inter-specific interaction. Inter-specific interaction means how different species interact with each other in the natural environment. In the natural environment, different species interact with each other. Inter-specific means between, specific means species. This means interaction between species. There are different types of interactions between species. One of them is coexistence. Apart from this, we have the example of competitive exclusion, the example of mutualism, the example of commensalism, parasitism, and predation. So, all these are basically the competitive. These are all the actually the inter-specific interactions. So, what is coexistence? First of all, we look at the word coexistence. So, coexistence means to exist altogether. So, coexistence is a phenomenon in which the animals, our organisms which are utilizing same resources, they live in same habitat. So, coexistence is a phenomenon in which the animals utilizing same resources are the animals having same type of requirements, they live in same type of environment, same type of habitat, same habitat, they live together. So, how this happens? Simply, if we talk identically or truly, if the ideal situation is that they are utilizing same resources, and every possible identical way of utilizing them, then ultimately, they will have a competition arise. And this means that a species will survive. But sometimes, the animals which are having same requirements, they utilize their resources in slightly different way. What will we do with our resources in a different way? We will utilize them. If one animal is utilizing resources in one way, other animal is utilizing same resources in another way. And third animal will utilize same resources in the third way. So, if the species or group of animal uses same resources in different patterns, then they can coexist, then they can coexist again. The example is the, here we have the MacArthur. MacArthur was a scientist who studied the five species of birds. He studied the red of the warbirds. So, warbirds, birds, they actually feed on caterpillar. And they feed on same type of caterpillar. Basically, MacArthur studied that five different species of warbirds, these are the birds, five species of birds, they are living on same type of trees, and they are having same type of food. He studied that why the competition is not coming. He noticed that actually, the five different species of birds, they are eating caterpillar at different positions of the tree. They are feeding on different positions of the tree. Some of them are feeding from below, some of them are feeding from the middle, some from the top, some from the side branches. So, they are feeding on different positions of the tree. That is why the competition is not coming. Actually, they have partitioned the resources. So, species can coexist if they partition the resources. If they partition the resources, they will say that they are a part of the region. If they separate them, then species can coexist. I will tell you where two boundaries overlap, competition will be present there. This is the explanation of the MacArthur experiment. In this, you can see that the tree is having five different types of species of birds. They are having same type of food. They eat the same type of food, caterpillar, caterpillars, insects, birds, where they eat. These are the same types of food. Now, how have they coexisted? How are they living in the same habitat? Actually, they have divided the feeding areas. You can see that they are feeding from the bottom, from the center, from the top. So, if you feed them on different positions, then they can coexist. So, coexistence is only when the resources are enough. So, if the resources are limited, or if the resources, the prior resources decrease, then what will happen in this case? The animals that coexist, they will compete with each other. When resources are depleted, resources are depleted, then the competition will rise. And the ultimate result will be the competitive exclusion. This means that coexistence will not exist. In fact, there will be a second pattern of inter-specific interaction, which is called competitive exclusion. Competitive exclusion means that when you compete with five species, one will survive, and the other four have to migrate from that tree. You have to migrate from that tree.