Our Environment — Class 6 Science (Samacheer Kalvi)
TN State Board (Samacheer Kalvi) Class 6 Science, Term 3 — Chapter 4. The living and non-living world around us.
1. About this chapter
This chapter covers the ecosystem and its components, food chains, biodegradable and non-biodegradable waste, pollution, and waste management (the 3 Rs).
2. The ecosystem
- An ecosystem is the living things and their physical surroundings together. Aquatic ecosystems include ponds, lakes, rivers (freshwater) and oceans like the Pacific.
- Components: producers (green plants, which make food), consumers — herbivores (plant-eaters), carnivores, omnivores — and decomposers (bacteria and fungi, which break down dead matter).
3. Waste and pollution
- Biodegradable wastes can be broken down by nature (a coconut shell, plant and animal wastes). Non-biodegradable wastes (plastics) cannot.
- Pollution is an undesirable change in air, water or soil. Pesticides and fertilizers running into water cause water pollution.
4. Managing waste — the 3 Rs
- Reduce, Reuse, Recycle. Recycling turns waste into new products; reuse uses things again. Schools sort waste into two categories (biodegradable / non-biodegradable).
5. Worked examples
Example 1. Which organisms are the producers in an ecosystem? Green plants.
Example 2. Is a coconut shell biodegradable? Yes, it is biodegradable.
Example 3. What do pesticides and fertilizers in water cause? Water pollution.
6. Book-back questions (Samacheer Kalvi)
I. Choose the correct answer
- An example of a freshwater ecosystem is — (a) only a pond / (b) all of them (pond, lake, river). Ans: (b) all of them.
- The producers in an ecosystem are the — (a) animals / (b) plants. Ans: (b) plants.
- A biodegradable waste is a — (a) plastic bottle / (b) coconut shell. Ans: (b) coconut shell.
- An undesirable change in air and water is called — (a) erosion / (b) pollution. Ans: (b) pollution.
- Pesticides and fertilizers cause — (a) noise pollution / (b) water pollution. Ans: (b) water pollution.
II. Fill in the blanks 6. Animals that eat only plants are called herbivores. 7. Recovering materials from waste to make new things is called recycling. 8. Using a thing again instead of throwing it away is called reuse.
III. True or False 9. Bacteria and fungi are decomposers. — True. 10. Human and animal wastes are non-biodegradable. — False (they are biodegradable). 11. Pesticides lead to air pollution. — False (they cause water pollution).
7. Common mistakes
- Mistake: Calling animals the producers. Fix: Green plants are the producers; animals are consumers.
- Mistake: Thinking plant and animal wastes are non-biodegradable. Fix: They are biodegradable; plastics are non-biodegradable.
- Mistake: Saying fertilizers cause air pollution. Fix: Pesticides and fertilizers cause water pollution.
8. Quick revision
- Term 3 · Ch 4 · our environment.
- Ecosystem = living things + surroundings; aquatic (pond, lake, river, ocean).
- Producers (plants), consumers (herbivores/carnivores/omnivores), decomposers (bacteria, fungi).
- Biodegradable (coconut shell, plant/animal waste) vs non-biodegradable (plastic).
- Pollution = undesirable change; pesticides/fertilizers → water pollution; follow the 3 Rs (reduce, reuse, recycle).
