Summary Garde 9, term 4. Natural Science, The earth as a system
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Course
Natural Science
Institution
9th Grade
An in dept, thorough, detailed, effective and efficient set of Natural Science study notes covering the section The earth as a system for grade 9 term 4 content. The notes are in the format of Summary, Self Test Questions and Answers.
Summary
- The Earth is a complex system comprising four interacting spheres: Biosphere, Atmosphere,
Lithosphere, and Hydrosphere.
- These spheres are vital for sustaining life on Earth and constantly interact with each other.
Biosphere:
- Definition: Consists of all living organisms.
- Living organisms rely on gases from the Atmosphere, water from the Hydrosphere, and nutrients
from the Lithosphere to survive.
- Organisms form ecological communities known as biomes.
- Examples of biomes include deserts, grasslands, and tropical rainforests.
- Biomes can be observed from space.
Atmosphere:
- Definition: The layer of air surrounding Earth.
- Composition: Approximately 78% nitrogen, 21% oxygen, with traces of other gases.
- Gravity keeps the Atmosphere in place.
Lithosphere:
- Definition: Comprises solid rock and soil, forming the Earth's solid surface.
- Encompasses continents and the land beneath oceans and seas.
- Source of minerals and metals.
Hydrosphere:
- Definition: Contains all forms of water on Earth, including solid, liquid, and gas.
- Includes water in oceans, rivers, lakes, and moisture in the air.
- Most Earth's water is saltwater, while only 3% is freshwater.
- Distribution of Earth's water: Freshwater (3%), Saline (oceans, 97%).
- Fresh surface water: Rivers (2%), Swamps (11%), Lakes (87%).
Structure of the Earth:
- 90% of freshwater is locked in polar ice.
- Extends from the Earth's surface into the lithosphere and upward into the atmosphere.
- Freshwater is a small portion and primarily frozen.
- The Earth consists of four concentric layers: Crust, Mantle, Outer Core, and Inner Core.
, Crust:
- Outermost layer, about 8 km deep beneath oceans and 50 km thick under continents.
- Comprised of loose materials like rocks, soil, and seabed.
Mantle:
- Located below the Crust, extending about 3000 km into Earth.
- Makes up 85% of Earth's total mass.
- Divided into hard rock, super-heated molten rock (magma), and solid rock layers.
Inner Core:
- Approximately 1,200 km thick.
- Likely a solid ball of iron, nickel, and minerals.
- Extreme temperatures and high pressure prevent melting.
Outer Core:
- About 2,300 km thick.
- Comprises super-heated molten lava of liquid iron and nickel.
- Responsible for generating Earth's magnetic field.
Self Test:
1. What are the four main Earth spheres, and how do they interact?
2. Explain the composition of the Atmosphere.
3. Define the Lithosphere and its significance.
4. Describe the Hydrosphere and the distribution of Earth's freshwater.
5. Identify the four layers that make up the Earth's structure.
Questions:
1. How do living organisms depend on interactions between Earth's spheres for survival?
2. Why is the Lithosphere important for the mining industry?
3. What is the primary factor that keeps the Atmosphere in place around Earth?
4. Discuss the significance of the Outer Core in terms of Earth's magnetic field.
1. What is the hydrosphere, and what does it include?
2. What percentage of Earth's water is fresh, and where is most of it found?
3. Describe the distribution of Earth's freshwater.
4. What are biomes in the biosphere, and how are they related to ecological communities?
5. Name a few examples of biomes.
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