Case Based Questions: Our Home: Earth, a Unique Life Sustaining Planet | Science Curiosity Class 8 - New NCERT PDF Download
Q 1: Read the source below and answer the questions that follow:
Ananya was working on her school project and used ISRO’s satellite images to study her village. From above, she noticed forests, farmlands, rivers, and houses all clearly marked. She realised satellite images show details that are not easily seen on the ground.
(a) How do satellite images help us understand Earth’s diverse landscapes? (1 mark)
(b) Why is it important to monitor changes in land use using such images? (1 mark)
(c) Suggest two ways this information can aid environmental conservation efforts. (2 marks)
Ans:
(a) Satellite images provide detailed views of large areas, showing physical features clearly.
(b) Monitoring changes helps detect deforestation, urban growth, and water depletion early.
(c) It helps plan sustainable land use and protect natural habitats by guiding policies.
Q 2: Read the source below and answer the questions that follow:
Rohan read that Earth is called the “Blue Planet” because almost 70% of its surface is covered with water. Looking at a globe, he saw huge oceans and lakes. He wondered why such liquid water is hardly found on other planets.
(a) What makes Earth’s position in the solar system ideal for liquid water? (1 mark)
(b) Why is liquid water essential for sustaining life? (1 mark)
(c) Explain how Earth’s atmosphere helps to maintain temperatures suitable for liquid water. (2 marks)
Ans:
(a) Earth lies in the habitable zone where temperatures allow water to stay liquid.
(b) Water is a solvent vital for chemical reactions and supports all living organisms.
(c) The atmosphere traps heat through greenhouse gases, preventing extreme temperatures, thus sustaining liquid water.
Q 3: Read the source below and answer the questions that follow:
Satvik’s teacher told the class that Earth has a magnetic field which protects life. To explain, Satvik placed a magnet under the paper and sprinkled iron filings. The way the filings curved reminded him of how Earth’s field deflects harmful solar particles.
(a) What role does Earth’s magnetic field play in sustaining life? (1 mark)
(b) How does the magnetic field protect Earth’s atmosphere from solar wind? (1 mark)
(c) What might happen to Earth’s surface if this magnetic protection did not exist? (2 marks)
Ans:
(a) It shields living beings from harmful cosmic rays and solar radiation.
(b) The magnetic field deflects charged particles of solar wind away from Earth.
(c) Without it, solar wind would strip away the atmosphere and increase lethal radiation, making life difficult.
Q 4: Read the source below and answer the questions that follow:
Sanika loved the forest near her town, but she noticed fewer birds, butterflies, and insects recently. On asking around, she learned that new construction had destroyed some trees. This made her wonder how biodiversity loss affects all living beings.
(a) What is biodiversity loss, and how does it affect ecosystems? (1 mark)
(b) Why is biodiversity important for food chains and human life? (1 mark)
(c) Suggest two actions Sanika’s community can take to help conserve biodiversity. (2 marks)
Ans:
(a) Biodiversity loss is the reduction or extinction of species, which disrupts ecosystem balance.
(b) Biodiversity supports food production, clean air, and medicine, crucial for survival.
(c) Actions include protecting habitats and implementing pollution control measures.
Q 5: Read the source below and answer the questions that follow:
In a farming village, summers became hotter and rains decreased over time. As a result, crops failed and the nearby river had fewer fish. The villagers worried that human activities might be worsening these changes.
(a) What human activities might be causing hotter summers and less rainfall? (1 mark)
(b) How does deforestation worsen these climatic changes? (1 mark)
(c) Propose two solutions that could help restore rainfall and improve crop and fish populations. (2 marks)
Ans:
(a) Burning fossil fuels increases greenhouse gases, causing global warming; deforestation reduces water vapour release.
(b) Trees release water vapour, aiding rainfall; cutting them reduces moisture and shade, causing heat.
(c) Solutions include reforestation to restore water cycles and reducing emissions to limit the temperature rise.
Q 6: Read the source below and answer the questions that follow:
While revising biology, Nisha compared how plants and animals reproduce. She learned that plants depend on pollination to transfer pollen, while animals use fertilisation. She noticed that some animals have external fertilisation, while others have internal fertilisation.
(a) What is the main difference between sexual reproduction in plants and animals? (1 mark)
(b) How does external fertilisation differ from internal fertilisation? (1 mark)
(c) Why is genetic variation important in sexual reproduction? (2 marks)
Ans:
(a) Plants use pollination to transfer pollen; animals have sperm that directly fertilise eggs.
(b) External fertilisation occurs outside the body in water; internal fertilisation occurs inside the female body.
(c) Genetic variation helps species adapt to changes and survive environmental challenges.
Q 7: Read the source below and answer the questions that follow:
A town close to a factory faced serious environmental issues. Smoke polluted the air, waste polluted the river, and many plants and animals began to disappear. People realised this was part of a bigger global problem.
(a) What are the three main components of the triple planetary crisis? (1 mark)
(b) How do pollution and habitat loss threaten biodiversity? (1 mark)
(c) Suggest three measures this town could adopt to address these environmental issues. (2 marks)
Ans:
(a) Climate change, pollution, and biodiversity loss.
(b) Pollution poisons ecosystems; habitat loss reduces living space for species, disturbing the balance.
(c) Promote renewable energy, improve waste management, and protect natural habitats.
Q 8: Read the source below and answer the questions that follow:
During a school trip, Raj and his friends observed forests, rivers, soil, and air in their region. Their teacher explained that these systems support each other. Raj understood that disturbing one system can upset the balance of life.
(a) Name the four Earth systems that interact to sustain life. (1 mark)
(b) Give an example of how the atmosphere and hydrosphere interact. (1 mark)
(c) Why is maintaining balance among these systems crucial for life? (2 marks)
Ans:
(a) Atmosphere, hydrosphere, geosphere, and biosphere.
(b) The atmosphere provides water vapour, leading to rainfall (hydrosphere), supporting ecosystems.
(c) Imbalance causes climate disruption, loss of habitats, and resource scarcity, threatening life.
Q 9: Read the source below and answer the questions that follow:
At a science fair, students displayed a model of India’s Mangalyaan mission to Mars. They explained that Mars has a thin atmosphere, a cold surface, and very little water. The project made them compare conditions on Earth and Mars.
(a) Why is studying Mars important for understanding Earth’s uniqueness? (1 mark)
(b) What challenges make Mars less suitable for life compared to Earth? (1 mark)
(c) How can space missions help us protect Earth’s environment? (2 marks)
Ans:
(a) It shows why Earth’s atmosphere and water make it uniquely habitable.
(b) Mars has a thin atmosphere and no stable liquid water, making it hostile for life.
(c) They improve understanding of climate, help develop technologies to mitigate Earth’s environmental issues.
Q 10: Read the source below and answer the questions that follow:
Sara placed a small plant inside a glass jar and kept it in sunlight. After some time, she felt that the air inside the jar was warmer than outside. This simple experiment reminded her of the greenhouse effect on Earth.
(a) What causes the temperature inside the jar to rise? (1 mark)
(b) How is this similar to the greenhouse effect on Earth? (1 mark)
(c) Why is the greenhouse effect important, and how can it become harmful? (2 marks)
Ans:
(a) Sunlight passes through the glass, warming the air inside, which is trapped, raising the temperature.
(b) Earth’s atmosphere traps heat similarly, preventing extreme temperature drops at night.
(c) It keeps Earth warm enough for life, but excess greenhouse gases cause overheating and climate change.
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FAQs on Case Based Questions: Our Home: Earth, a Unique Life Sustaining Planet - Science Curiosity Class 8 - New NCERT
| 1. What makes Earth a unique life-sustaining planet? |  |
| 2. How does Earth’s atmosphere contribute to life? | |
| 3. What are the key components of Earth’s ecosystems? | |
| 4. Why is water considered essential for life on Earth? | |
| 5. How have human activities impacted Earth’s environment? | |
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