This MCQ module is based on: Life, Resilience and Protecting Earth
TOPIC 49 OF 50
Life, Resilience and Protecting Earth
🎓 Class 8
Science
CBSE
Theory
Ch 13 — Chemical Effects of Electric Current
⏱ ~29 min
🌐 Language: [gtranslate]
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Life — Tougher Than You Think
Life on Earth is astonishingly stubborn. Wherever there is even a whisper of water and energy, some organism seems to find a way to survive. Scientists have discovered living creatures in places once thought completely hostile — boiling hot springs, deep polar ice, the pitch-black ocean floor, acidic lakes, and even the outside of the International Space Station!
- How can living things survive at temperatures where nothing human-made could last?
- If life is so tough, why are species disappearing from Earth at an alarming speed?
- What are we doing to our only home — and what are we doing to protect it?
13.10 Life in Extreme Places — The Extremophiles
Organisms that thrive in conditions most living things cannot tolerate are called extremophiles. They show us how amazingly adaptable life can be.
Tardigrades
Microscopic "water bears" that survive boiling, freezing, vacuum of space and strong radiation by entering a dried-up state called cryptobiosis.
Antarctic Bacteria
Bacteria living in ice sheets at −20 °C. Their cells contain "antifreeze" proteins that prevent ice crystals from forming.
Thermophiles
Microbes that thrive in boiling hot springs at 80 °C or more — like the colourful bacteria of Yellowstone and Tattapani (HP).
Deep-Sea Creatures
Tube worms, giant crabs and anglerfish surviving kilometres below the ocean surface under crushing pressure and pitch darkness, near hot hydrothermal vents.
Desert Animals
Camels store fat in their humps, barely sweat, and can drink 100 L of water in minutes. Kangaroo rats can go a whole life without drinking!
Polar Fish
Arctic icefish have transparent blood and special proteins so they don't freeze in sub-zero sea water.
What Extremophiles Teach Us
Studying extremophiles excites scientists for two big reasons. First, they broaden the search for extraterrestrial life — if microbes can live under Antarctic ice on Earth, perhaps something similar survives under the frozen oceans of Europa (Jupiter's moon) or Enceladus (Saturn's moon). Second, they give us useful tools: for example, an enzyme taken from a hot-spring bacterium is used in every modern DNA test, including COVID-19 tests!
13.11 Life's Adaptability
Even in ordinary conditions, every living thing has features that fit it for its environment — this is called adaptation. Polar bears have thick white fur; cacti store water in their stems; lotus plants float with waxy leaves; fish have gills to absorb oxygen dissolved in water. The same chapter of life is written in thousands of different local dialects across forests, deserts, mountains and oceans.
Biodiversity: The enormous variety of living things on Earth — animals, plants, fungi, microbes — and the many ecosystems they form. India alone is home to over 90,000 animal species and 45,000 plant species.
13.12 Threats to Our Unique Planet
Sadly, the same intelligent species that built rockets and vaccines is also, at present, the single biggest threat to Earth's life-support systems.
Climate Change
Burning coal, petrol, diesel and natural gas releases huge amounts of carbon dioxide into the atmosphere. Like a thickening quilt, this extra CO₂ traps more of the Sun's heat — a strong greenhouse effect. The result is rising sea levels, melting glaciers, more intense cyclones, heatwaves, and unpredictable monsoons — all affecting farmers, coastal cities and wildlife.
Pollution
Smoke from factories and vehicles pollutes the air; sewage and chemicals poison our rivers and groundwater; pesticides degrade soil; and plastic waste chokes the oceans. Scientists have even found microplastics in mountain snow, in fish, and in human blood.
Species Extinction
When forests are cut or wetlands drained, the animals and plants living there lose their homes. Today species are going extinct — disappearing forever — about 1,000 times faster than the natural rate. The tiger, the Great Indian Bustard and countless insects are on the edge.
Ozone Depletion
Certain industrial gases called CFCs (chlorofluorocarbons), once used in refrigerators and spray cans, destroyed ozone molecules high in the stratosphere. A dangerous "hole" was spotted above Antarctica in 1985, letting harmful UV rays reach the surface.
13.13 Global Agreements — Working Together
Because the atmosphere is shared by all nations, protecting it needs cooperation across borders. Two landmark treaties show that this is possible.
| Agreement | Signed | Goal | Result |
|---|---|---|---|
| Montreal Protocol | 1987 | Phase out ozone-destroying CFCs worldwide. | Nearly every country signed. The ozone layer is now healing — expected to fully recover by around 2060. |
| Paris Agreement | 2015 | Limit global warming to well below 2 °C (ideally 1.5 °C) above pre-industrial temperatures. | 196 countries agreed to cut greenhouse gas emissions and report progress every five years. |
Why it matters: The Montreal Protocol is often called "the most successful environmental treaty in history" — a reminder that when science, policy and public action come together, even the biggest planetary problems can be solved.
13.14 India's Green Contributions
India has emerged as an important voice for the planet's health. A few highlights:
- International Solar Alliance (ISA): Launched by India and France in 2015, the ISA now brings together more than 100 countries to promote solar energy — a clean, renewable source that does not emit greenhouse gases.
- Ban on single-use plastics (2022): India outlawed thin plastic bags, straws, cutlery and several other single-use items to reduce plastic waste and protect waterways and marine life.
- Forest cover: India's forest and tree cover has been growing slowly — a rare achievement among rapidly developing countries.
- Mission LiFE (Lifestyle for Environment): Encourages every citizen to adopt earth-friendly habits — saving energy, reducing waste, conserving water.
- Project Tiger & Project Cheetah: Protect endangered big cats and restore balance in forests.
13.15 Sustainable Living — Your Role
Save Energy
Switch off fans, lights and chargers when not needed. Use LED bulbs. Prefer walking or cycling for short distances.
Save Water
Close taps while brushing. Harvest rainwater. Report leaks. Reuse water from washing vegetables to water plants.
Reduce, Reuse, Recycle
Carry a cloth bag to market. Refill bottles. Segregate wet and dry waste. Avoid single-use plastic.
Plant & Protect
Grow trees wherever possible. Protect birds and insects in your garden — they are part of the food web.
🌱 Activity 13.3 — My One-Week Earth Diary
You will need: a notebook, a pen.
- Divide a page into three columns: Date / What I Did for Earth / What I Could Have Done Better.
- Every evening for 7 days, note down one earth-friendly action (e.g. closed the tap while brushing, carried a cloth bag, switched off the fan on leaving the room) and one earth-harming action you could improve on.
- At the end of the week, count how many good actions you recorded.
- Pick ONE habit to carry forward permanently.
🔍 Predict: Which area — energy, water, or waste — do you think you personally waste the most? Write your guess before the week starts.
Most students discover at least one surprise — leaking taps, unused chargers left plugged in, or food thrown away each day. Even tiny daily changes, multiplied across our 1.4 billion population, save enormous amounts of resources.
The activity shows that protecting Earth is not only the job of governments and scientists. Every home, every classroom and every child is part of the solution.
🎯 Competency-Based Questions
Rahul's grandfather tells him that when he was a boy, their village well never went dry even in summer, birds of many colours came every morning, and the air smelt fresh. Today, the well runs dry by April, few birds are left, and smoke hangs over the nearest town. Rahul wonders what has changed.
Q1. L1 Remember What do we call organisms that can survive in very hostile conditions like boiling water or polar ice?
Answer: They are called extremophiles. Examples include tardigrades, Antarctic bacteria and hot-spring thermophiles.
Q2. L2 Understand Why is the Montreal Protocol often called the most successful environmental treaty in history?
Answer: Almost every country on Earth signed and honoured it, CFC production dropped sharply worldwide, and the ozone layer has measurably started to recover. Few other agreements can show such a clear, global environmental improvement caused directly by united human action.
Q3. L3 Apply Rahul's village has started running out of groundwater. Suggest three specific steps the villagers could take, linking each to a concept you have learnt in this chapter.
Answer: (i) Rainwater harvesting — catch monsoon rain to recharge wells, because only a tiny share of Earth's water is accessible fresh water. (ii) Plant more trees — their roots hold groundwater and cool the local climate. (iii) Avoid wasteful irrigation — use drip irrigation or mulching to cut evaporation, protecting the shrinking 1% of Earth's water we can use.
Q4. L4 Analyse Analyse how studying extremophiles can help in the search for life on other planets.
Answer: Extremophiles show that life can survive far beyond "comfortable" conditions. If simple organisms on Earth live in hot vents, polar ice, or toxic lakes, similar life forms could possibly survive under the frozen oceans of Europa or in the briny soil of Mars. Thus, knowing what extremophiles need widens the range of places and chemicals where astronomers now look for alien life.
Q5. L5 Evaluate Evaluate the statement: "Environmental protection is the duty of the government alone."
Answer: The statement is incorrect. Governments can make laws (plastic ban, forest protection, vehicle emission rules) and sign treaties (Paris Agreement, Montreal Protocol), but these only work if citizens, industries, farmers and students change their daily habits. Pollution, water waste and deforestation happen house by house; so their fixes — saving electricity, carrying cloth bags, planting trees — also have to happen house by house. Environmental protection is a shared responsibility.
🔗 Assertion–Reason Questions
Assertion (A): Tardigrades can survive the vacuum of outer space.
Reason (R): They can enter a dry, dormant state called cryptobiosis in which their metabolism almost stops.
Answer: A. Cryptobiosis — essentially shutting down life processes — is exactly what lets tardigrades survive extreme cold, radiation and vacuum.
Assertion (A): The ozone layer has begun to recover.
Reason (R): The Paris Agreement of 2015 banned the use of CFCs.
Answer: C. A is true, but R is false — CFCs were phased out by the Montreal Protocol of 1987. The Paris Agreement deals with climate change (CO₂ and other greenhouse gases), not ozone-destroying chemicals.
Assertion (A): India launched the International Solar Alliance (ISA) to promote renewable energy.
Reason (R): Solar energy is a clean source that does not release greenhouse gases like burning coal does.
Answer: A. Reducing greenhouse gas emissions is exactly why many countries, led by India and France, promote solar energy through the ISA — R directly explains A.
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