Nature's Treasures
Class 6 Science — Chapter Notes & Complete Learning Material
Introduction
One day, Riya and Aman were walking through a beautiful forest when they met an old wise man sitting under a big tree. He smiled and asked, "Do you know the greatest treasures in the world?"
Riya quickly said, "Gold and diamonds!" Aman added, "Maybe money?"
The wise man laughed and pointed around them. "The real treasures are all around you - the air you breathe, the water in the rivers, the sunlight that warms you, the trees that give fruits, and the soil that grows food. Without these, life wouldn't exist."
Riya and Aman looked around in wonder. They realised that nature had been giving them these gifts every day, yet they had not thought of them as treasures.
Natural treasures are the elements and resources that nature provides. They are essential for the survival of all living beings and for improving our quality of life. These treasures include air, water, sunlight, soil, plants, animals and minerals. We also make many useful things from these resources; such items created by human beings are called human-made resources. This chapter explains these natural treasures and why we must protect them for a better future.
1. Air
Air is the invisible mixture of gases that surrounds the Earth and is essential for life. It is often simply called the atmosphere when we speak of the layer that envelops the planet.
What is air made of?
Nitrogen (about 78%): the largest component; it does not support burning.
Oxygen (about 21%): essential for respiration and combustion.
Other gases (about 1%): includes argon, carbon dioxide, neon, helium, methane, and water vapour (and a few others).
Characteristics and importance of air
Air is colourless and transparent.
It occupies space and exerts pressure.
Air supports life: animals and plants exchange gases (oxygen and carbon dioxide) with the air.
Aquatic animals obtain dissolved air from water to breathe.
Oxygen in the air is essential for the human body; without it, the body cannot function for more than a few minutes.
Moving air is called wind; wind causes many observable effects such as rustling leaves, swaying branches and moving clouds.
2. Water
Water is vital for life. The Earth's surface is covered by water over about three-fourths of its area, but only a small part of this - about 2.6% - is fresh water suitable for drinking and most uses. Water is often described as a renewable resource, but fresh water can become scarce due to overuse and pollution.
Our body contains approximately 70% water. We use water for drinking, cooking, bathing, washing, agriculture, industry and many other purposes.
Uses of water in daily life
Drinking: to keep the body hydrated and healthy.
Cooking: preparation of food and beverages.
Bathing and personal hygiene: personal cleanliness and health.
Washing: clothes, utensils and household cleaning.
Agriculture: irrigation and care of crops.
Industries: used in manufacturing processes and cooling.
Because water is precious, we should use it carefully and avoid wasting it.
Sources of water
Rivers: flowing freshwater used for drinking, irrigation and industry.
Lakes: inland standing freshwater bodies used for many local needs.
Ponds: smaller water bodies used locally.
Wells: provide groundwater that can be drawn for use.
Water pollution and conservation
Water pollution occurs when harmful substances, wastes or rubbish enter freshwater bodies like rivers, lakes and ponds. Polluted water is unsafe for drinking and harms plants and animals.
Freshwater sources are limited and unevenly distributed; many areas face water shortages. This makes conservation and pollution prevention essential.
Methods to conserve water include fixing leaks, using water-saving taps, reusing greywater where safe, practising drip irrigation in farming and encouraging water-wise habits at home and school.
Rainwater harvesting
Rainwater harvesting is a method to collect and store rainwater for use. It helps replenish groundwater and provides water for household and agricultural uses, especially where fresh water is scarce.
Technique involved in rainwater harvesting
1. Collect rainwater from rooftops or paved areas into gutters and pipes.
2. Use a wire mesh or filter at the inlet to remove leaves and large debris.
3. Route the water into storage tanks or recharge pits that contain layers of sand, gravel and charcoal to filter finer impurities.
4. Allow cleaned water to be stored in tanks or used to recharge groundwater through soakaways, trenches or recharge wells.
Traditional methods used in India include stepwells (for example Bawadi in Rajasthan and Vav in Gujarat) and lined trenches to increase water seepage into the ground.
World Water Day is observed on 22 March each year to highlight the importance of conserving water and keeping it clean. Think: how can you conserve water at home and school?
3. Energy from the Sun
The Sun is the main source of energy for the Earth. It provides light and heat that make life possible.
Ways we use the Sun's energy
Plants: make food using sunlight through photosynthesis; this is the basis of food chains.
Solar panels: convert sunlight into electricity.
Can be used directly for cooking (solar cookers) and for heating water (solar water heaters).
The Sun drives the water cycle by causing evaporation, which leads to cloud formation and rainfall.
4. Forests
Forests are large areas covered with many trees, shrubs, grasses, animals and birds. They are extremely important for the environment and for human life.
Importance of forests
Forests provide oxygen and absorb carbon dioxide, so they are often called the "lungs of the Earth".
They supply wood, food, medicines and other useful products.
Forests are a home for wildlife such as tigers, elephants, deer and many birds and insects.
They help prevent soil erosion, regulate climate and maintain the water cycle.
Forest conservation
Forest cover has been decreasing because of tree cutting for farming, housing and industry.
Growing a new forest or restoring a lost forest takes a long time; therefore, conservation and responsible use are important.
Van Mahotsav and community actions
Van Mahotsav is a week-long festival celebrated in July to promote tree plantation and awareness about forests. Community participation during Van Mahotsav helps increase green cover.
5. Soil, Rocks and Minerals
Soil
Soil is made of small particles of rock, decayed plants and animals, air, water, minerals and living organisms such as insects and microbes.
When living things die and decompose, they add nutrients to the soil and make it fertile.
Soils vary in colour and texture depending on the materials present and the climate of the area.
Soil formation is a slow process caused by the weathering of rocks by the Sun, water, wind and living organisms.
Different soils are suitable for different plants; some soils are good for agriculture while others are better for making bricks.
Rocks
Rocks are found everywhere and are used for building houses, roads and other structures.
Some rocks, such as slate, are used for roofing; laterite can be used to make bricks.
Common rocks include granite, sandstone and marble.
For thousands of years humans used rocks to make tools such as hand axes and arrowheads.
Minerals
Rocks are made of minerals, and metals such as aluminium, iron, copper and gold are obtained from minerals.
Minerals are used to manufacture items like airplanes, cars, jewellery, cosmetics and electronic equipment.
Even simple mobile phones contain many minerals such as gold, silver, copper and cobalt.
Formation of many rocks and minerals takes thousands to millions of years, so they must be used carefully and conserved.
6. Fossil Fuels
Fossil fuels are energy sources formed from the remains of plants and small organisms that were buried under layers of soil and rock millions of years ago. With heat and pressure over long periods, these remains changed into fuels such as coal, petroleum and natural gas.
Petroleum: yields products such as petrol, diesel and kerosene.
Natural gas: is used for cooking, electricity generation and in some vehicles as Compressed Natural Gas (CNG). It is cleaner-burning than petrol or diesel.
Coal: is mainly used for generating electricity and in some industries.
Fossil fuels: satisfy energy needs but are non-renewable: they exist in limited amounts and cannot be replaced quickly once used.
Environmental impact
Burning fossil fuels releases smoke and carbon dioxide, which pollutes the air and contributes to global warming.
Heavy reliance on fossil fuels for transport and household energy has caused large-scale air pollution in many places.
How to conserve fossil fuels
Use public transport, walk or cycle for short trips.
Combine errands or use car-pooling to reduce vehicle use.
Use energy-efficient appliances at home and switch off lights and fans when not in use.
Explore and support alternative energy sources such as solar and wind energy.
7. Natural Resources: Renewable and Non-renewable
Natural resources are materials and energy provided by nature that we use to satisfy our needs. Based on how quickly they are replaced by natural processes, natural resources are classified as renewable and non-renewable.
Renewable resources: are those that can be naturally replenished within a reasonable period. Examples: air, water, forests, sunlight.
Non-renewable resources: are present in limited amounts and cannot be replenished quickly. Examples: minerals, rocks, fossil fuels (coal, petroleum, natural gas).
Human-made resources are things created by people from natural resources to meet our needs, for example: electric bulbs, furniture, solar panels, bicycles and buildings.
8. Resources We Use
Common natural resources used every day include air, water, soil, plants and animals.
Key resources that support life and production include sunlight, forests, rocks, minerals and fossil fuels.
Because these resources come from nature, we must conserve them and avoid wasting them so that future generations also have access to them.
9. Key Points (Summary)
Natural resources are materials provided by nature that help sustain life and meet human needs.
Natural resources are divided into renewable and non-renewable types based on whether they can be replenished naturally within a reasonable time.
Human-made resources are produced by people using natural resources.
Air is essential for breathing and combustion; it is mainly nitrogen and oxygen.
Water is essential for life and many human activities; it must be conserved and kept free from pollution.
The Sun is the main source of energy for Earth; it supports plant growth and can be harnessed for electricity and heating.
Forests support biodiversity, protect soil and help control climate; they should be conserved.
Soil forms slowly from rocks and organic matter and is vital for growing food.
Rocks and minerals are used in construction and manufacturing; they take a long time to form and should be used wisely.
Fossil fuels are non-renewable and burning them causes air pollution; we must reduce dependence on them and use alternatives.
Conservation of natural resources is essential for sustainability and the well-being of future generations.
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