Air, Water, Earth and Sky
Components of Environment and Their Interdependence
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Overview
This topic forms the foundational core of Environmental Studies (EVS) at the primary level. It introduces children to the four major components of our natural environment and how they work together to support life on Earth. For MAHA TET, questions typically test factual recall about composition, properties, and the cyclic relationships between these components.
Understanding this topic is essential because it builds the conceptual framework for later topics like ecosystems, weather, natural resources, and pollution. Expect 2-4 questions in Paper I that assess your knowledge of basic facts (composition of air, layers of atmosphere, water cycle stages) as well as your ability to explain interdependence in child-friendly terms suitable for primary teaching.
Mastery requires knowing specific percentages, layer names in correct order, and the ability to trace how one component affects others—skills directly tested in MCQ format.
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Key Concepts
- **Environment** comprises all living (biotic) and non-living (abiotic) things surrounding us; air, water, earth and sky are the four abiotic pillars children first learn.
- **Air (Atmosphere)** is a mixture of gases forming a protective blanket around Earth; it is colourless, odourless, occupies space, and has weight.
- **Composition of Air**: Nitrogen 78%, Oxygen 21%, Carbon dioxide 0.03%, Argon and other gases ~1%, plus variable water vapour and dust particles.
- **Layers of Atmosphere** (bottom to top): Troposphere → Stratosphere → Mesosphere → Thermosphere → Exosphere; weather occurs in troposphere, ozone layer lies in stratosphere.
- **Water (Hydrosphere)** covers about 71% of Earth's surface; 97% is saline (oceans), only 3% is freshwater, and of that, most is locked in glaciers and ice caps.
- **Water Cycle (Hydrological Cycle)**: Evaporation → Condensation → Precipitation → Collection/Runoff → Evaporation (continuous cycle driven by solar energy).
- **Earth (Lithosphere)** is the solid outer layer comprising crust, mantle and core; soil—the topmost layer—supports plant life and is formed over thousands of years.
- **Sky** in primary EVS refers to the visible expanse above Earth, including clouds, sun, moon, stars; it helps children understand day-night, seasons, and weather phenomena.
- **Interdependence**: Plants use carbon dioxide from air and water from soil to make food (photosynthesis), releasing oxygen; animals breathe oxygen, exhale carbon dioxide; rain replenishes water bodies and soil moisture—each component sustains others.