Our Home: Earth, a Unique Life Sustaining Planet Class 8 (Curiosity)

Q 1
Question
What is one major reason Mars cannot currently support life like Earth?
(i) It has too many volcanoes.
(ii) It is too close to the Sun.
(iii) It lacks a thick atmosphere and liquid water.
(iv) Its magnetic field is too strong.
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Q 2
Question
Which of these is an example of geodiversity?
(i) Variety of bird chirping in a forest.
(ii) Different landforms like mountains, valleys, and deserts.
(iii) Changing weather during monsoons.
(iv) Number of different types of fish in a pond.
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Q 3
Question
If the Earth were smaller with the same density, what might happen to its atmosphere?
(i) It would become thicker and hotter.
(ii) It would escape into space due to weaker gravity.
(iii) It would become frozen.
(iv) It would cause stronger winds.
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Q 4
Question
In sexual reproduction, why are offspring different from their parents?
(i) They grow in different climates.
(ii) They eat different food.
(iii) They acquire new instructions after birth.
(iv) They get mixed instructions (genes) from both parents.
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Q 5
Question
You notice tiny green plants growing in cracks on your school wall after the monsoon. Where do you think the seeds came from? What conditions helped these plants grow there?
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Q 6
Question
A city has recently cut down a large patch of forest to build new roads and buildings. Discuss the possible effects this could have on the local climate and biodiversity? How might this affect water availability or quality in the area?
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Q 7
Question
A friend says, "The Earth has always had climate changes in the past, so today's global warming is nothing new." How would you respond using what you've learnt in this and other chapters of your science book?
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Q 8
Question
Imagine Earth's magnetic field suddenly disappeared. What kinds of problems could arise for life on Earth? Explain.
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Q 9
Question
You are tasked with designing a new settlement for humans on Mars. Name three things you would need to recreate from Earth to support human life there. Which of these do you think is the hardest to replicate, and why?
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Q 10
Question
In a village, the temperature has been increasing and rainfall has become unpredictable over the past few years. What could be causing this change? Suggest two ways the village could adapt to these new conditions.
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Q 11
Question
If there were no atmosphere on the Earth, would it affect life, temperature, and water on the planet? Explain.
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Q 12
Question
Discuss five examples of vegetative propagation.
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Project 1
Project
Design an 'Earth Survival Kit'. Imagine you're building a tiny model of Earth for another planet. What must it have to support life, and why?
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Key Points
A survival kit needs air, water, warmth, soil and living things.
Key Points / Good Practices
Include breathable air with oxygen for respiration.
Add liquid water for drinking and for plants.
Provide a warmth source to keep the right temperature.
Include soil with nutrients so plants can grow.
Add plants to make food and oxygen, and decomposers to recycle.
Protect it from harmful rays, like Earth's atmosphere and magnetic field.
A working kit copies Earth's air, water, warmth, soil and life.

Project 2
Project
India is planning for a challenging lunar mission, Chandrayaan-4, which will bring back samples of soil from the Moon. If the Moon had water, could plants grow in that soil? Think of some experiment that could help you explore whether plant growth is possible on the Moon.
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Key Points
A simple pot experiment can test if plants grow in Moon soil with water.
Key Points / Good Practices
Take samples of Moon-like soil returned by the mission.
Plant the same seeds in Moon soil and in Earth soil.
Add water, air and sunlight to both equally.
Keep one Moon-soil pot without water as a control.
Watch which seeds sprout and how well they grow.
Compare results to see if water lets plants grow in Moon soil.
A fair test compares plant growth in Moon and Earth soil.

Project 3
Project
Flowers are often brightly coloured and have a pleasant smell. How do you think these features help the plant reproduce?
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Key Points
Bright colour and smell attract insects that help pollination.
Key Points / Good Practices
Bright colours catch the eyes of bees, butterflies and birds.
A pleasant smell draws insects from a distance.
Insects come to drink the flower's nectar.
While feeding, they pick up and carry pollen.
This carries pollen from flower to flower — pollination.
So colour and scent help the plant reproduce and make seeds.
Colour and scent attract pollinators that spread pollen.

Project 4
Project
Why do animals like fish and frogs lay hundreds or even thousands of eggs at a time, while other animals lay only a few? What might be the advantages and disadvantages of laying so many eggs?
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Key Points
Laying many eggs helps a few survive, but most are lost.
Key Points / Good Practices
Fish and frogs leave their eggs in water without much care.
Many eggs are eaten by predators or do not survive.
So laying thousands means at least a few will grow up.
Advantage: it improves the chance some young survive.
Disadvantage: most eggs are wasted and a lot of energy is spent.
Animals that protect their young can lay only a few.
Many eggs raise survival chances when there is no parental care.

Project 5
Project
Birds like sparrows build nests and care for their eggs and chicks, while reptiles like snakes usually lay their eggs and leave them without protection. How might this difference in parental care affect the chances of survival for the young ones in each case?
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Key Points
Parental care raises survival, so fewer young are needed.
Key Points / Good Practices
Sparrows build nests and feed and guard their chicks.
So a high share of their young survive to grow up.
Snakes lay eggs and leave them unprotected.
So many of their young are eaten before they grow.
Animals with care can have fewer young safely.
Animals without care must lay more eggs to make up for losses.
More parental care means more young survive with fewer eggs.