These comprehensive RBSE Class 9 Science Notes Chapter 14 Natural Resources will give a brief overview of all the concepts.
RBSE Class 9 Science Chapter 14 Notes Natural Resources
→ The resources available on the Earth and the energy from the Sun are necessary to meet the basic needs of all life forms on the Earth.
→ Life on Earth depends on resources like soil, water, air and energy of the Sun.
→ All the varieties of material we get from nature to meet our basic needs are called natural resources.
→ Resources on the Earth : Natural resources are obtained from the three components of the earth. These components are
- Lithosphere : It is the outer solid crust of the Earth. Its upper thin weathered: layer is called soil.
- Hydrosphere : It is the water component of the Earth. Water covers 75% of the Earth’s surface.
- Atmosphere : It is the blanket of air that covers the whole Earth.
→ The life supporting zone of Earth where the lithosphere, hydrosphere and atmosphere interact and makes life possible is called biosphere.
→ It may be biotic or abiotic components.
Biotic Components : Plants and animals.
Abiotic Components : Air, water and soil.
→ The breath of life : Air
→ Air is a mixture of various gases like nitrogen, oxygen, carbon dioxide and water vapour. All living beings need oxygen to get energy for their activities. On Venus and Mars there is no life because carbon dioxide constitutes 95-97% of the atmosphere.
The percentage of carbon dioxide in our atmosphere is a mere fraction of a percent because it is fixed in two ways :
- Green plants convert carbon dioxide into glucose by photosynthesis.
- Marine animals use carbonates dissolved in sea-water to make their shells.
→ Role of Atmosphere in Climate Control : Atmosphere keeps the average temperature of Earth steady during the day and whole year, because air is a bad conductor of heat. The atmosphere does so by preventing the sudden increase in temperature during the daylight hours. During the night, it slows down the escape of heat into the outer space. In contrast, the situation on the Moon is quite different which is about the same distance from the Sun that the Earth is. Moon has no atmosphere and the temperature on the surface of the Moon ranges from -190°C to 110°C.
→ The movement of air : Winds
(i) The atmosphere gets heated from the solar radiation that is reflected back by the land or water bodies. As a result of heating convection currents are set up in the air. The air over land gets heated faster than air above water bodies, – because land gets heated faster than water.
(ii) In coastal regions, during day, the air above the land gets heated faster and starts rising. So, a low pressure region is created and air over sea moves into area of low pressure. Movement of air from a region of high pressure to a region of low pressure is causes wind.
(ii) During the day, the direction of wind would be from sea to land and at night, both land and sea starts to cool. Water cools down slower than the land so air above water would be warmer than air above land, so, the direction of wind would be from land to sea.
→ Air Pollution : Air contaminated with smoke, fumes, dust, pollen grain, etc. which can affect on health and vegetation seriously is called air pollution. Substances that cause air pollution are called pollutants. E.g. oxides of sulphur and nitrogen.
→ Harmful effects of air pollution :
→ In humans : Respiratory and renal problems, eye irritation, high blood pressure, cancer, tuberculosis, etc.
→ In plants : Degeneration of chlorophyll, reduced growth, mottling of leaves.
→ Acid rain : Oxides of sulphur and nitrogen combine with water to form sulphuric acid and nitric acid respectively. When these acids dissolve in water, they fall on the earth as rain, that is called acid rain. It causes death of aquatic plants, reduces the fertility of soil, contaminate food and drinking water.
→ Water : It is found on Earth’s surface and 3 /4th or 75% of the Earth’s surface is covered by water. Maximum water is salty (97%), fresh water (wonder liquid) consitutes about 3%. Substances are transported from one part to other part of the body in a dissolved form. Hence, organisms need to maintain the level of water within their bodies to stay alive. Rain water harvesting improves the availability of fresh water.
→ Water Pollution : When water becomes unfit for consumption or when addition of undesirable substances to water and removal of desirable substances from water is occur then it is called water pollution. It is the contamination of water bodies such as lakes, rivers, oceans and groundwater caused by human activities, which can be harmful to organisms and plants that live in these water bodies.
→ Mineral riches in the soil : Soil is the uppermost crust of the earth and a major physical component of the environment. It supports terrestrial plants and animals including us. The Sun, water, wind and living organism such as lichens are some factors which help in the formation of soil. It contains soil particles, humans and living organisms.
→ Soil Pollution : Contamination of soil by organic and toxic substances which negatively affect the fertility of the soil. Fertilisers and pesticides destroy the soil structure. Solid wastes from homes, offices and vegetable and fruit markets when dumped on land, lead to soil pollutoin.
→ Biogeochemical cycles : Movement of nutrient element through the living and non-living component of biosphere, is called biogeochemical cycles.
→ Water Cycle: Water from various sources evaporates, condenses and again precipitates as rain, falls on land, flows back in the sea and river is called as water cycle.
→ Nitrogen Cycle : The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature. Carbon Cycle : The carbon cycle is the biogeochemical cycle that describes the transformations of carbon in nature.
→ Oxygen Cycle : The oxygen cycle is the biogeochemical cycle that describes the movement of oxygent within and between its three main reservoirs : the atmosphere (air), the biosphere (living things), and the lithosphere Earth’s crust.
→ Greenhouse effect : An increase in percentage of some gases as carbon dioxide, methane in atmosphere stops the heat to escape. This results in an increase in the average temperature of earth. This is called greenhouse effect. The carbon dioxide is called greenhouse gas.
→ Ozone layer depletion : Three atoms of oxygen (O3) is called as ozone. The ozone is poisonous but absorbs harmful radiations from the Sun. Ozone layer is present in stratosphere. Man-made components like CFCs persist in the atmosphere and react with ozone molecules and deplete the ozone layers. It may cause Cancer.
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