Name the 'triple planetary crisis,' as the chapter defines it.
Hint. Three named environmental challenges, grouped under one umbrella term.
✦ 'Today, the biggest environmental challenges that we face are climate change, biodiversity loss, and pollution — together known as the triple planetary crisis.'
Trace the chain of cause and effect from burning fossil fuels to global warming, explaining why Earth can no longer keep its natural balance.
Hint. Earth normally has a way of absorbing carbon dioxide — the problem is a mismatch of speed, not a total absence of absorption.
✦ Burning fossil fuels like coal and oil releases greenhouse gases like carbon dioxide and methane, which trap even more heat in the atmosphere, causing global warming. Normally, Earth keeps a balance since trees, plants, and even tiny ocean planktons absorb carbon dioxide as they grow — but burning fossil fuels releases extra carbon that has been locked underground for millions of years, and the Earth cannot absorb this fast enough, so the heat builds up rather than being offset the way it normally would be.
List four specific consequences of even a small increase in global temperature, as named in the chapter.
Hint. The chapter names melting, rising, extreme, and disappearing, each tied to a different part of the Earth system.
✦ Even a small increase in temperature can: melt ice caps, raise sea levels (which could flood many coastal cities), cause extreme weather conditions, and lead to many plants and animals disappearing. Together, these long-term changes in temperature, rainfall, and weather patterns are what the chapter calls climate change, since it is exactly this combination the term refers to.
Using Chapter 12's own reasoning, explain how destroying a natural habitat can affect a whole food chain, not just the plants directly removed.
Hint. The chapter deliberately reuses an example almost identical to Chapter 12's own grass-hare-fox food chain.
✦ When natural habitats are destroyed, plants and animals may disappear, upsetting ecosystems — for example, if grasses vanish, animals that feed on them like deer or grasshoppers struggle to survive. And without herbivores, predators like tigers or foxes lose their food too, since every type of living thing has a role, and losing even a few weakens nature's ability to support life as a whole, not just the specific plants that were destroyed.
List three specific harms caused by air pollution, according to the chapter.
Hint. Air pollution's harm reaches beyond human lungs alone.
✦ Air pollution from factories, vehicles, and burning fuels can cause breathing problems, damage crops, and lead to smog and acid rain — harming both people directly and the wider natural environment.
Name the four global environmental agreements mentioned in the chapter, their stated years, and what each one specifically addressed.
Hint. Two of the four target a specific chemical/gas problem directly; the other two set up broader ongoing international cooperation.
✦ The Montreal Protocol (1987) helped reduce harmful chemicals like chlorofluorocarbons (CFCs), allowing the ozone layer to slowly recover. The Earth Summit (1992) led to international efforts on climate change and biodiversity. The Kyoto Protocol (2005) and the Paris Agreement (2015) committed countries to reduce greenhouse gas emissions, with the Paris Agreement specifically setting a goal to limit global warming to below 1.5 °C — a goal the chapter notes the world is not on track to meet, since global emissions as of 2025 remain too high to stay under that limit.
Ever heard of... list two specific harms caused by water and soil pollution, as described in the chapter.
Hint. One harm affects living things directly in the water; another travels through a whole chain to reach humans eventually.
✦ Factory, farm and plastic waste harm aquatic life and make water unsafe. Excess fertilisers and poor waste disposal pollute soil, reduce crop yield, and spread harmful substances through the food chain — which means soil pollution doesn't stay contained to the soil itself, but can travel through crops and into the food people eventually eat.
Why does the chapter state that 'damage to one [Earth system] can affect the others'? Give an example connecting two different systems.
Hint. The four Earth systems from earlier in the chapter reappear here, now framed around vulnerability rather than just definition.
✦ The chapter states: 'the Earth system, such as hydrosphere, biosphere, atmosphere and geosphere are connected — so damage to one can affect the others.' For example, air pollution (damaging the atmosphere) can lead to acid rain, which then damages soil and water quality (the geosphere and hydrosphere), which in turn can harm crops and aquatic life (the biosphere) — showing how a problem starting in just one system can cascade through all four.
Solutions written by the tuition.in editorial team and checked against NCERT Curiosity — Textbook of Science for Grade 8, Chapter 13 (hecu113.pdf), Reprint 2026-27, pages 210-228. Questions are referenced from the NCERT textbook for identification.
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