Nature’s Treasures
Full, detailed solutions — every in-text prompt and every exercise question from the chapter, with the original textbook figures.
(Reflective question — a sample answer.)
Yes. Besides pure air, fertile soil, sunlight and trees, other treasures of nature include water (rivers, lakes, rain), forests, rocks and minerals, animals and birds, fossil fuels (coal and petroleum) and wind. All of these enrich our lives and are needed for the survival of living beings.
(Activity-based — a sample answer.)
Most of us can hold our breath only for a short time (about 30–60 seconds). While holding it, we feel uncomfortable and restless and get a strong urge to breathe.
Air is a mixture of gases. It mainly contains nitrogen (78%) and oxygen (21%), along with about 1% of argon, carbon dioxide and other gases in small quantities.
When you run holding the firki, or blow air on it, or move it back and forth, it spins. It is the moving air (wind) that makes the firki rotate.
A windmill works on the same principle — wind turns its wings. Windmills are used to run flour mills, pull up water from wells, and generate electricity at windmill farms.
(Fill-in-the-blank — sample answers.)
Besides drinking, we use water for cooking, bathing, washing clothes and utensils, cleaning the house, growing crops (farming) and for industries.
| Activity | How water is wasted | Way to reduce wastage |
|---|---|---|
| Hand washing | Keeping the tap running while soaping hands. | Wet hands, turn off tap, then use soap; open tap only to rinse. |
| Washing clothes | Using too much water / running tap for each cloth. | Wash in a bucket; reuse the rinse water for cleaning floors. |
| Washing utensils | Letting the tap run continuously. | Soap all utensils first with tap off, then rinse together. |
| Taking shower | Long showers use a lot of water. | Use a bucket and mug, or take shorter showers. |
| Cooking | Washing vegetables under a running tap. | Wash in a bowl of water; use leftover water for plants. |
| Gardening | Over-watering / watering in hot sun. | Water in the early morning/evening; water only the roots. |
| Brushing teeth | Tap left running while brushing. | Turn off the tap; use a glass of water to rinse. |
The statement that the cow gets its energy from the Sun is correct.
Although the cow eats grass, grass is a green plant that makes its own food using sunlight. So the energy stored in the grass originally came from the Sun. When the cow eats the grass, that energy passes into the cow.
Just standing in the Sun does not give the cow food energy — but the grass it eats was made using the Sun’s energy, so the Sun is the ultimate source.
(Prediction — sample answers.)
Point 1 is already given (we may have to depend on artificial lighting even during the daytime). Two more consequences:
2. Plants would not be able to make their food properly, because photosynthesis needs sunlight — this would lead to a shortage of food for animals and humans.
3. It would become cold; we could not dry clothes or grains, and solar panels and solar cookers would not work.
(Discussion — sample answers.)
From forests we get: wood / timber, fruits, honey, medicines (medicinal herbs), gum, rubber, paper, fuelwood, lac and spices. (Any five.)
(Creative task — key points.)
Large-scale cutting of forests leads to: loss of home and shelter for wild animals and birds, loss of biodiversity, less rainfall, soil erosion, more carbon dioxide and air pollution, and problems like floods, droughts and climate change. It takes many years to grow a forest back.
(Sample answers.)
Besides walking/cycling and using public transport, we can: carpool / share rides, use CNG or electric vehicles, switch off engines at red lights, use solar energy, use energy-efficient appliances, and avoid wasting electricity (much of it is made from coal).
(Sample answers.)
Use electric vehicles, use public transport / carpool, walk or cycle for short distances, use CNG instead of petrol/diesel, plant more trees, use clean energy (solar, wind), and avoid burning waste.
| Activity | Natural resource used |
|---|---|
| Washing clothes | Water (given) |
| Making clay toys | Soil (clay) |
| Collecting firewood | Forest / trees (wood) |
| Making kites | Paper (from trees) and thin bamboo sticks |
| Having breakfast | Food from plants and animals; water |
| Cooking food | Natural gas / LPG (fossil fuel) and water |
| Item (Fig. 11.9) | Jumbled name | Correct name | Type |
|---|---|---|---|
| Water tap (running water) | atwre | Water | Renewable |
| Windmill | ndiw | Wind | Renewable |
| Forest | refost | Forest | Renewable |
| Rock | ocrk | Rock | Non-renewable |
True (i) Nature has all the resources to meet human needs.
True. Nature provides air, water, soil, sunlight, forests, minerals and fossil fuels — all the resources needed to sustain life.
False (ii) Machines are a resource found in nature.
False. Machines are made by human beings — they are human-made resources, not natural resources.
True (iii) Natural gas is a non-renewable resource.
True. Natural gas is a fossil fuel that takes millions of years to form and is present in limited quantity.
True (iv) Air is a renewable resource.
True. Air is continuously renewed by natural processes (for example, plants release oxygen), so it is a renewable resource.
(i) A fuel commonly used in two-wheelers like scooters or bikes is ______
- (a)Kerosene
- (b)Petrol
- (c)Diesel
- (d)LPG
(ii) An example of a renewable resource is ______
- (a)Coal
- (b)Water
- (c)Natural gas
- (d)Petrol
| Resource | Classification |
|---|---|
| Coal | Non-renewable |
| Natural gas | Non-renewable |
| Forests | Renewable |
| Minerals | Non-renewable |
Forests can be replenished within a reasonable time, so they are renewable. Coal, natural gas and minerals take millions of years to form and get exhausted once used.
Petroleum is formed from the remains of tiny organisms and plants that were buried deep inside the earth and slowly changed over millions of years. It is found in limited quantities, and once we use it up, it cannot be replaced within a reasonable period of time (making it again would take millions of years). For these reasons, petroleum is called a non-renewable resource.
A forest is much more than a group of trees — it is a whole community of many types of trees, shrubs, herbs, animals, birds, insects and tiny organisms that grow and depend on one another over hundreds of years. Trees take many years to grow to full size, and the fertile soil, moisture and balance among living beings also build up very slowly. So once a forest is destroyed, it cannot be regrown quickly — restoring it takes a very long time.
| Daily activity | Natural resource | Way to reduce use |
|---|---|---|
| Drinking & cooking | Water | Close taps when not in use; don’t waste water. |
| Cooking food | LPG / natural gas | Use a pressure cooker; cook efficiently. |
| Travelling | Petrol / diesel | Walk, cycle or use public transport. |
| Lighting & electricity | Coal | Switch off lights/fans when not needed; use solar power. |
| Eating food | Plants & animals (soil) | Avoid wasting food. |
1. Breathing — living beings use the oxygen in air to survive.
2. Burning of fuels — combustion needs oxygen from the air.
3. Windmills generating electricity / running flour mills and pumping water.
4. Flying kites, sailing boats and drying clothes (also pollination and seed dispersal by wind).
Plant more trees and saplings; take part in Van Mahotsav and tree-plantation drives; water and care for young plants; protect existing trees and avoid cutting them; maintain gardens in home, school and parks; and create awareness among friends and neighbours about the importance of trees.
(i) Type of energy used: Solar energy — the heat and light energy of the Sun. The curved reflector focuses sunlight onto the pot to cook the food.
(ii) One benefit and one drawback:
Benefit: it is free, clean and renewable and causes no pollution (it saves fuels like LPG).
Drawback: it works only in bright sunlight — it cannot be used at night, on cloudy or rainy days, and cooking is slower.
The roots of trees hold the soil together and stop it from being washed or blown away. Fallen leaves decay and add nutrients (humus), keeping the soil fertile and moist.
When trees are cut on a large scale, the roots no longer bind the soil, so rain and wind cause soil erosion. The soil also loses its nutrients and moisture, becoming dry and infertile. This is why large-scale tree cutting lowers soil quality.
Way 1: Burning fossil fuels in vehicles (petrol/diesel) releases smoke and carbon dioxide into the air.
Way 2: Burning coal and waste in factories and homes releases harmful gases and smoke.
Solar panels: would stop generating electricity, because they need sunlight. The family would have to depend on another source of electricity.
Gas stove: would still work — it uses LPG/natural gas, not sunlight — so cooking can continue.
Windmill: would still pump water as long as the wind blows, so this task can continue.
Trees are very important — they give us oxygen, hold the soil together, provide shelter to wildlife, help bring rain, and absorb carbon dioxide.
Cutting them on a large scale for industries and housing is not fully justified, because it causes air pollution, soil erosion, loss of animal homes and climate change. Some development is necessary, but it must be balanced with conservation: we should plant more trees than we cut, use alternatives (like recycled materials), and avoid large-scale deforestation. This way both people’s needs and nature are protected.
Steps: fix all leaking taps; make sure taps are fully closed after use; use buckets/mugs instead of running taps; reuse water (e.g. RO-reject water for plants and floors); set up rainwater harvesting; put up awareness posters; and appoint water monitors to check usage.