This Class 4 Science lesson explains the concept of a food chain, its links (producers, consumers, decomposers), and the predator-prey relationship. It gives examples like Grass → Rabbit → Fox and describes competition among organisms for limited resources. The lesson discusses human impacts on ecosystems—such as deforestation, pollution, and overhunting—and how these disrupt food chains. It also outlines ways humans can protect ecosystems, including planting trees, protecting animals, reducing pollution, conserving water, and raising community awareness. Activities include observing local ecosystems and creating food chains from real-life examples.