Our Home: Earth, a Unique Life Sustaining Planet
1. 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.
Answer: (iii) It lacks a thick atmosphere and liquid water.
2. 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.
Answer: (ii) Different landforms like mountains, valleys, and deserts.
3. 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.
Answer: (ii) It would escape into space due to weaker gravity.
4. 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.
Answer: (iv) They get mixed instructions (genes) from both parents.
5. 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?
Answer: The seeds may have come from nearby plants and trees. They could have been carried by wind, birds, insects, or water (rain) and got trapped in the cracks of the wall.
Conditions that helped the plants grow:
- Moisture and water from the monsoon rains
- Small amount of soil or dust collected in the cracks
- Sunlight for photosynthesis
- Air for respiration
These conditions allowed the seeds to germinate and grow into tiny green plants.
6. 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?
Answer: Cutting down a large forest area to build roads and buildings can affect the climate and living organisms in many ways.
It may make the local climate hotter and drier because trees help keep the air cool and support rainfall. It also leads to loss of biodiversity, as many plants and animals lose their natural habitat.
Deforestation can also affect water availability and quality. Without tree roots to hold the soil, soil erosion may occur, which can make nearby rivers and lakes muddy. It can also reduce groundwater recharge, leading to less water availability in the area.
7. 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?
Answer: It is true that the Earth’s climate has changed in the past, but today’s global warming is different. Earlier climate changes happened very slowly over thousands or millions of years due to natural causes.
However, the current warming is happening much faster and is mainly caused by human activities like burning fossil fuels, deforestation, and pollution. These activities increase greenhouse gases in the atmosphere, which trap more heat and raise the Earth’s temperature.
So, while climate change has happened before, the speed and human cause of today’s global warming make it a serious problem.
8. Imagine Earth’s magnetic field suddenly disappeared. What kinds of problems could arise for life on Earth? Explain.
Answer: If Earth’s magnetic field disappeared, several problems could occur for life on Earth.
The magnetic field protects Earth from harmful solar radiation and charged particles from the Sun. Without it, these particles could reach the surface and damage living cells and increase health risks for humans and animals.
It could also disturb satellites, communication systems, and power grids. Many animals like birds and turtles that use Earth’s magnetic field for navigation might also become confused during migration.
So, the magnetic field is very important because it protects life and supports many natural and technological systems on Earth.
9. 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?
Answer: To support human life on Mars, we would need to recreate some important conditions found on Earth:
- Breathable air (oxygen) for humans to breathe.
- Water for drinking, growing food, and daily needs.
- Suitable temperature and shelter to protect people from extreme cold and radiation.
The hardest to replicate would likely be a stable atmosphere with the right temperature and pressure, because Mars has a very thin atmosphere and no strong magnetic field. Creating and maintaining Earth-like conditions on a whole planet would require very advanced technology.
10. 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.
Answer: The change could be caused by climate change, deforestation, or increased pollution, which can lead to higher temperatures and irregular rainfall.
The village could adapt in the following ways:
- Harvest and store rainwater to manage water during dry periods.
- Plant more trees and grow drought-resistant crops to reduce heat and protect farming.
These steps can help the village cope with changing climate conditions and protect their water and food supply.
11. If there were no atmosphere on the Earth, would it affect life, temperature, and water on the planet? Explain.
Answer: Yes, if Earth had no atmosphere, it would greatly affect life, temperature, and water.
- Life: Living organisms would not survive because there would be no oxygen to breathe and no protection from harmful solar radiation.
- Temperature: The atmosphere helps trap heat. Without it, Earth would experience extreme temperatures—very hot during the day and very cold at night.
- Water: Liquid water would not remain on the surface; it would evaporate or freeze, making it difficult for life to exist.
Therefore, the atmosphere is essential for protecting life and maintaining stable conditions on Earth.
12. Discuss five examples of vegetative propagation.
Answer: Vegetative propagation is a type of asexual reproduction in plants where new plants grow from parts of the parent plant such as roots, stems, or leaves.
Five examples are:
- Potato – It grows from underground stems called tubers. The “eyes” of the potato grow into new plants.
- Ginger – It reproduces through rhizomes, which are underground stems that grow horizontally.
- Strawberry – It grows new plants through runners (long stems that grow along the ground).
- Bryophyllum – New plants grow from buds on the edges of its leaves.
- Onion – It reproduces through bulbs, which grow underground and develop into new plants.
These methods allow plants to produce new plants quickly without seeds.
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