Human-Made Ecosystems and Sustainable Farming (12.9.1–12.9.2) — "How Nature Works in Harmony"

1. 12 marks

   Give three examples of human-made ecosystems, and explain the one key way they differ from natural ecosystems.

   Hint. The chapter's whole point about these ecosystems is what they need that a forest or pond doesn't.

   ✦ Fish ponds, farms, and parks are examples of human-made ecosystems. Unlike natural ecosystems, which sustain themselves, human-made ecosystems 'need human care and management' to keep functioning — though, since they are well designed, they can still help reduce pollution, support biodiversity, and provide recreational spaces for people.

2. 23 marks

   What was the Green Revolution, and what specific problem in India did it respond to?

   Hint. The chapter gives an exact time period and the exact crisis that triggered the shift.

   ✦ Between 1950 and 1965, India faced a food crisis due to low crop production. In response, the mid-20th century saw the use of tractors, machines, synthetic fertilisers, and pesticides to increase food production — which is why this period is known as the Green Revolution.

3. 34 marks

   Why are Green Revolution-style farming methods now considered unsustainable, according to the chapter?

   Hint. Three separate practices are named as the source of the problem.

   ✦ These methods are now considered unsustainable because of the overuse of synthetic chemicals, excessive groundwater extraction, and growing only one type of crop for commercial gain (monoculture). Many scientists believe overusing pesticides and repeatedly growing the same crop on the same land leads to soil degradation.

4. 44 marks

   Explain how overusing synthetic fertilisers can end up increasing the pest problem it was meant to help control.

   Hint. The chain runs through soil microorganisms and natural predators, not just through the crop itself.

   ✦ Overuse of synthetic fertilisers may reduce soil fertility by decreasing friendly microorganisms in the soil and lowering organic matter (humus), which helps bind soil particles — without enough humus, soil becomes prone to erosion. It also reduces the population of natural predators, which ultimately increases the population of pests — which means a practice intended to boost crop growth can end up undermining the very natural pest control an ecosystem otherwise provides.

5. 53 marks

   What is monoculture, and what two problems does the chapter say it causes?

   Hint. One problem affects the ecosystem's variety of species; the other affects a group of organisms crops directly depend on.

   ✦ Monoculture is growing the same crop repeatedly on the same land. The chapter states it 'can reduce biodiversity and affect pollinators, which are crucial for food production' — which means it harms both the overall variety of species present and the very pollinators that crops need to reproduce.

6. 63 marks

   Our scientific heritage: what does the ancient text Vrikshayurveda recommend for soil health, and how does Kunapa Jala fit into this?

   Hint. The text's core message is about ongoing soil care, not a one-time treatment.

   ✦ The ancient text Vrikshayurveda emphasises the continuous nourishment of the soil through organic manure, strongly advocating practices like using Kunapa Jala — a liquid fertiliser made from animal and plant waste through the process of fermentation, which breaks complex substances into simpler ones — alongside other composted materials, since this reflects an ongoing, sustainable approach to soil care that predates modern organic farming by centuries.

Solutions written by the tuition.in editorial team and checked against NCERT Curiosity — Textbook of Science for Grade 8, Chapter 12 (hecu112.pdf), Reprint 2026-27, pages 190-209. Questions are referenced from the NCERT textbook for identification.