NCERT Class 9 Science Chapter 14 NATURAL RESOURCES Notes

NCERT Class 9 Science Chapter 14 NATURAL RESOURCES Notes 

Earth's Life-Supporting Systems

• Introduction to Earth's Life-Supporting Resources
• Essential Resources: Land, water, air
• Energy Source: Sun
• Earth's Crust: Lithosphere
• Water Coverage: 75%, part of the hydrosphere
• Air Coverage: Atmosphere
• Life-Supporting Zone: Biosphere (interaction of lithosphere, hydrosphere, and atmosphere)

Biosphere Components:

• Biotic: Living organisms
• Abiotic: Air, water, soil
• 14.1 The Breath of Life: Air
• Air Composition: Mixture of nitrogen, oxygen, carbon dioxide, water vapor
• Comparison with Other Planets: Venus and Mars have atmospheres dominated by carbon dioxide (95-97%)

Role of Oxygen:

• Needed by eukaryotic and many prokaryotic cells for energy production
• Produced by plants through photosynthesis and marine animals through shell formation
• Carbon Dioxide Fixation:
• Photosynthesis in plants
• Marine animals using carbonates for shells

14.1.1 The Role of the Atmosphere in Climate Control

• Insulation: Air is a poor conductor of heat
• Temperature Regulation:
• Keeps Earth's temperature steady
• Prevents sudden temperature increases during the day
• Slows heat loss at night
• Example: Moon's temperature ranges due to lack of atmosphere

14.1.2 The Movement of Air: Winds

• Air Movement: Caused by heating of air and water vapor formation
• Convection Currents: Heated air rises, creating low pressure, drawing in cooler air
• Coastal Winds:
• Day: Air moves from sea to land (land heats faster)
• Night: Air moves from land to sea (land cools faster)
• Influencing Factors: Earth's rotation, mountain ranges

14.1.3 Rain

• Cloud Formation and Rain:
• Water evaporates, rises, cools, and condenses into droplets
• Dust particles act as nuclei for droplets
• Droplets grow, fall as rain when heavy
• Forms of Precipitation: Rain, snow, sleet, hail
• Rainfall Patterns: Influenced by wind patterns, monsoons, and depressions

14.1.4 Air Pollution

• Pollutants: Nitrogen and sulfur oxides from burning fossil fuels
• Effects:
• Acid rain
• Smog (suspended particles, hydrocarbons)
• Health issues: Allergies, cancer, heart diseases

14.2 Water: A Wonder Liquid

• Distribution:
• Surface and underground water
• Saline water in seas and oceans
• Freshwater in ice caps, rivers, lakes, ponds
• Importance of Water:
• Medium for cellular processes
• Transport of substances in dissolved form
• Terrestrial life needs fresh water

14.2.1 Water Pollution

• Sources:
• Fertilizers and pesticides
• Sewage and factory waste
• Industrial cooling processes

Effects:

• Addition of undesirable substances (e.g., mercury salts, disease-causing organisms)
• Removal of desirable substances (e.g., dissolved oxygen)
• Temperature changes affecting aquatic life 

14.1 The Breath of Life: Air

Composition of Air:

• Air is a mixture of gases: nitrogen, oxygen, carbon dioxide, and water vapor.
• Earth's air composition is influenced by life on Earth.
• Venus and Mars have atmospheres mostly composed of carbon dioxide (95-97%).

Role of the Atmosphere in Climate Control:

• The atmosphere acts as a blanket, moderating Earth's temperature.
• Prevents rapid temperature increases during the day and slows heat loss at night.
• The moon, without an atmosphere, experiences extreme temperature variations (-190ºC to 110ºC).

Movement of Air: Winds:

• Caused by the heating of air and formation of water vapor.
• Land heats and cools faster than water, creating pressure differences that cause wind.
• Coastal winds flow from sea to land during the day and from land to sea at night.

Rain Formation:

• Water bodies heat up, causing evaporation.
• Warm air rises, cools, and condenses, forming clouds and precipitation.

Air Pollution:

• Fossil fuels release nitrogen and sulfur oxides, leading to acid rain and smog.
• Increased air pollution is linked to allergies, cancer, and heart diseases.

14.2 Water: A Wonder Liquid

Importance of Water:

• Water is essential for cellular processes and transportation of substances in organisms.
• Freshwater is crucial for terrestrial life-forms.
• Water Pollution:
• Fertilizers, pesticides, sewage, and industrial waste pollute water bodies.
• Changes in water temperature and composition can harm aquatic life.

14.3 Mineral Riches in the Soil

Soil Formation:

• Soil is formed from the breaking down of rocks by physical, chemical, and biological processes.
• Factors contributing to soil formation:
• Sun: Expansion and contraction of rocks due to temperature changes.
• Water: Freezes in cracks, expands, and wears down rocks.
• Wind: Erodes rocks and carries particles.
• Living organisms: Lichens and roots break down rocks.

Soil Composition:

• Soil is a mixture of rock particles, decayed organisms (humus), and microorganisms.
• Quality of soil depends on humus content and microorganisms.

Soil Pollution:

• Fertilizers and pesticides can destroy soil structure and kill microorganisms.
• Soil erosion occurs when topsoil is washed away by water or wind, especially in deforested areas.

14.4 Biogeochemical Cycles

Water Cycle:

• Water evaporates, condenses to form clouds, and returns as rain.
• Not all water flows back immediately; some infiltrates the soil and becomes groundwater.

Nitrogen Cycle:

• Nitrogen gas (78% of atmosphere) is converted to usable forms (nitrates/nitrites) by bacteria and lightning.
• Plants use these forms to make proteins, which are consumed by animals.
• Decomposition and denitrifying bacteria return nitrogen to the atmosphere.

Carbon Cycle:

• Carbon exists as CO2 in the atmosphere, carbonates in minerals, and in organic molecules in organisms.
• Photosynthesis converts CO2 into glucose, which is used by organisms for energy.
• Respiration and decomposition return CO2 to the atmosphere.