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The building blocks of plants, animals and humans are identical, and are made of the four elements - carbon, oxygen, nitrogen and hydrogen.
These elements are present in the environment - in air, water and soil. However, only green plants can absorb nitrogen from the soil through their roots, and use sunlight and water to produce energy by a process called photosynthesis. They are known as producers.
Animals and humans, who have plants or other animals as their food, are known as consumers. The chain that links consumers to producers is called the food chain or web.
Every living creature is found in a food chain. There are several food chains and they can be complex or simple depending on the environment.
To cite some examples, grasshoppers eat grass and are in turn eaten by frogs; snakes eat frogs and rodents.
Thus the importance of each and every creature in the web of life is evident. Tampering with the food chain only produces negative results, leading to the destruction of the species.
Every time a species becomes extinct, the chain is broken and many species, including humans, move closer to extinction.