CBSE Class 8 Annual Assessment

Chapter 12: How Nature Works in Harmony

Summary

This chapter studies how living and non-living things interact to keep nature in balance. A habitat provides the conditions an organism needs to live, and it has biotic components (plants, animals, microbes) and abiotic components (air, water, soil, sunlight, temperature). Organisms of the same kind in a habitat form a population, different populations sharing a habitat form a community, and a community interacting with its abiotic surroundings forms an ecosystem, which may be aquatic or terrestrial. The chapter shows how a change in one part of an ecosystem, such as fish affecting dragonfly numbers and therefore pollinators and seed production, ripples through the whole system. Organisms are classified by how they feed: producers (autotrophs) make their own food by photosynthesis, consumers (heterotrophs) include herbivores, carnivores, and omnivores, and decomposers (saprotrophs) like fungi and bacteria break down dead matter and recycle nutrients. Feeding relationships are shown as food chains, which interlink into food webs, with each level called a trophic level. Other relationships include competition, mutualism, commensalism, and parasitism. Ecosystems provide humans with air, water, food, medicine, and climate regulation, but human activities like deforestation, pollution, and overuse threaten them, as seen in the Sundarbans. The chapter ends with sustainable, eco-friendly farming as a way to protect soil health and biodiversity.

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