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the soil to prepare food by photosynthesis. In the process, oxygen is released, which is needed for respiration. Wehavelearnt,radiationfromtheSunheatstheEarth.Some of this heat is trapped by the atmosphere due to the greenhouse effect. This effect though mild, keeps the temperature just high enough for water to remain in the liquid state. In Curiosity, Grade 7,youalsolearntaboutheattransferbyradiation.Without an atmosphere, the Earth would lose heat to space and become too cold. So the greenhouse effect helps keep the Earth warm. Water is essential for life. You have learnt that it covers about 70 per cent of the Earth’s surface and is found in ponds, lakes, rivers,springs,seas,oceans,andgroundwater. All this water forms the hydrosphere. In Chapter 7, you learnt that water is a good solvent. In Curiosity, Grade 7, we learnt how water transports nutrients from soil to leaves in plants. In animals, it regulates body temperature, aids digestion, and ensures hydration, all essential for health and life. Though much of Earth is covered by Fig. 13.8: Life in water water, we still know little about what lives deep in the oceans. The hydrosphere is home to millions of life forms, from tiny planktons to giant whales, many still being discovered. Oceans, lakes, and rivers provide rich environments for aquatic life (Fig. 13.8). Freshwater is also needed to grow crops and support people around the world. Water vapour in the air forms clouds and brings rain or snow. This refills rivers, lakes, and underground water. Rainfall affects the kinds of plants and animals that can live in a place. Moving air also shapes weather and rainfall — which influence farming, water supply, and life on land. 13.4.2 Soil, rocks, and minerals Beneath our feet lies something remarkable — the Earth’s crust, made of rocks, soil, and minerals. It may seem hard and lifeless, but it provides almost everything life needs to grow and survive. From soil that helps plants grow to minerals that give us salt, coal, oil, and metals like iron and copper  — this outer layer support both ecosystems and human life. The solid parts of the Earth, including materials like rocks, soils, and minerals are known as the geosphere. Soil may look like simple dirt, but it is rich in nutrients like nitrogen and potassium that plants need to grow. These nutrients come from the slow breakdown of rocks and the remains of plants and animals. 218 Curiosity — Textbook of Science for Grade 8 Reprint 2026-27