Natural Resources Short Notes || Class 9 Science
Natural Resources
- Natural resources are materials or substances that occur in nature and can be used for economic gain.
- They are essential for the survival and development of life on Earth.
Types of Natural Resources:
- Biotic Resources: Derived from living organisms (e.g., forests, animals, fossil fuels).
- Abiotic Resources: Derived from non-living things (e.g., water, air, minerals, sunlight).
Components of the Earth:
- Lithosphere: The outer crust of the Earth, consisting of rocks and minerals.
- Hydrosphere: All the water on Earth’s surface, including oceans, rivers, lakes, and underground water.
- Atmosphere: The layer of gases surrounding the Earth, essential for life.
Biosphere
The biosphere is the life-supporting zone of the Earth where the atmosphere, hydrosphere, and lithosphere interact to make life possible.
Components:
- Biotic Components: These include all living organisms, such as plants, animals, and microorganisms.
- Abiotic Components: These include non-living elements like air, water, and soil.
Air
Composition of Air:
- Air is a mixture of gases, primarily nitrogen (78%) and oxygen (21%).
- It also contains small amounts of carbon dioxide, water vapor, and other gases like argon and helium.
Role of the Atmosphere:
- The atmosphere acts as a blanket, maintaining the Earth’s temperature by preventing sudden increases during the day and slowing down heat loss at night.
- It protects living organisms from harmful solar radiation.
Air Pollution:
- An increase in the content of harmful substance (pollutants) in the air like carbon dioxide, carbon monoxide, oxides of sulphur, nitrogen, fluoride, lead, nickel, arsenic and dust particles etc. causes air pollution.
Causes Of Air Pollution :
• In humans: Respiratory and renal problems, high blood pressure, eye irritation, cancer.
• In plants: Reduced growth, degeneration of chlorophyll, mottling (patches/spots of colour) of leaves.
Rain
Water Cycle
- Rain is a crucial part of the water cycle, which includes evaporation, condensation, and precipitation.
- Water from oceans, rivers, and lakes evaporates due to the sun’s heat, forming water vapor.
- This vapor rises, cools, and condenses to form clouds.
- When the clouds become heavy, the water falls back to Earth as rain.
GreenHouse Effect
The main greenhouse gases include carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), and water vapor. These gases absorb and emit infrared radiation, contributing to the warming of the atmosphere
• Effect of Increase in carbon dioxide (CO2):
- Global Warming: Higher temperatures due to trapped heat.
- Extreme Weather: More frequent and severe weather events.
- Ocean Acidification: Harmful effects on marine life.
- Health Issues: Poor air quality and spread of diseases.
- Ecosystem Disruption: Negative impacts on biodiversity.
Smog
Smog is a thick, fog-like layer in the atmosphere, especially common in urban areas. It is formed by the combination of smoke and fog.
Water: A wonderful Liquid
Importance of Water: Water is essential for all living organisms. It is involved in various biological processes, such as digestion, transportation of nutrients, and temperature regulation1.
Properties of Water: Water is a colorless, tasteless, and odorless liquid. It has unique properties like high specific heat, surface tension, and the ability to dissolve many substances, making it a universal solvent..
Distribution of Water: About 71% of Earth’s surface is covered by water, but only 3% of this is freshwater. The rest is saltwater found in oceans and seas. Freshwater is crucial for drinking, agriculture, and other human activities.
Water Pollution: Human activities, such as industrial discharge and agricultural runoff, lead to water pollution. Contaminated water can cause health problems and harm aquatic life.
Soil
- Soil is a vital natural resource that supports plant growth by holding roots and supplying water and nutrients.
- It is essential for agriculture, which provides food, clothing, and shelter.
Soil Composition:
- Soil is made up of minerals, organic matter, water, and air.
- The organic matter includes decomposed plants and animals, known as humus.
Soil Formation:
- Soil is formed through the weathering of rocks by wind, water, and climate.
- The process of soil formation is influenced by factors like parent material, climate, vegetation, and time.
Soil Erosion
Soil erosion is the process by which the top layer of soil is removed by natural forces such as wind and water.
Causes of Soil Erosion:
- Water: Heavy rainfall can wash away the topsoil, especially on slopes.
- Wind: Strong winds can blow away loose soil, particularly in dry and barren areas.
- Deforestation: Cutting down trees reduces the roots that hold the soil together, making it more prone to erosion.
- Overgrazing: When animals graze excessively, they remove the vegetation cover, exposing the soil to erosion.
- Agricultural Practices: Certain farming techniques, like plowing, can disturb the soil and make it more susceptible to erosion.
Biogeochemical Cycle
Definition: Biogeochemical cycles are the movement of elements like carbon, nitrogen, oxygen, and water between living (biotic) and non-living (abiotic) components of the environment.
Major Cycles:
- Water Cycle: Evaporation, condensation, precipitation, and infiltration.
- Carbon Cycle: Photosynthesis, respiration, decomposition, and combustion.
- Nitrogen Cycle: Nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.
- Oxygen Cycle: Photosynthesis and respiration.
Importance: These cycles ensure the recycling of essential nutrients, maintaining ecosystem balance.
Oxygen Cycle
Definition:
- The oxygen cycle is the process by which oxygen is exchanged between the atmosphere, biosphere, and lithosphere.
Key Processes:
- Photosynthesis: Plants release oxygen into the atmosphere as a by-product of photosynthesis.
- Respiration: Animals and plants consume oxygen for respiration and release carbon dioxide.
- Decomposition: Decomposers break down dead organisms, using oxygen and releasing carbon dioxide.
- Combustion: Burning of fossil fuels and organic matter consumes oxygen and releases carbon dioxide.
Importance:
- The oxygen cycle is crucial for maintaining the balance of oxygen in the atmosphere, which is essential for the survival of most life forms on Earth.
Carbon Cycle
Definition:
- The carbon cycle is the process by which carbon is exchanged among the atmosphere, oceans, soil, and living organisms.
Key Processes:
- Photosynthesis: Plants absorb carbon dioxide (CO₂) from the atmosphere to produce glucose and oxygen.
- Respiration: Animals and plants release CO₂ back into the atmosphere through respiration.
- Decomposition: Decomposers break down dead organisms, releasing carbon back into the soil and atmosphere.
- Combustion: Burning of fossil fuels and organic matter releases CO₂ into the atmosphere.
Importance:
- The carbon cycle is essential for regulating the Earth’s climate and maintaining the balance of CO₂ in the atmosphere.
Nitrogen Cycle
Definition:
- The nitrogen cycle is the process by which nitrogen is converted into various chemical forms as it circulates among the atmosphere, soil, and living organisms.
Key Processes:
- Nitrogen Fixation: Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) by bacteria or through industrial processes.
- Nitrification: Conversion of ammonia into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) by nitrifying bacteria.
- Assimilation: Plants absorb nitrates from the soil and use them to make proteins and other compounds.
- Ammonification: Decomposition of organic matter by decomposers, releasing ammonia back into the soil.
- Denitrification: Conversion of nitrates back into nitrogen gas (N₂) by denitrifying bacteria, releasing it into the atmosphere.
Importance:
- The nitrogen cycle is essential for making nitrogen available in a form that plants and other organisms can use, maintaining the balance of nitrogen in the ecosystem.