Soil, Rocks, Minerals and the Geosphere (13.4.2) — "Our Home: Earth, a Unique Life Sustaining Planet"

1. 12 marks

   Define the geosphere, in the chapter's own words. Why does the chapter warn against underestimating it?

   Hint. The definition names three specific materials; the warning is about a common first impression.

   ✦ 'The solid parts of the Earth, including materials like rocks, soils, and minerals are known as the geosphere.' The chapter warns that the geosphere 'may seem hard and lifeless, but it provides almost everything life needs to grow and survive' — which means its unassuming, non-living appearance can hide just how essential it actually is.

2. 23 marks

   List examples of materials the geosphere provides, and explain how these support both ecosystems and human life.

   Hint. The chapter names both growing-related materials and materials people extract and use directly.

   ✦ The chapter names soil that helps plants grow, and minerals that give us salt, coal, oil, and metals like iron and copper. This outer layer supports both ecosystems (through soil that plants need to grow, feeding the whole food chain built on producers) and human life directly, since extracted minerals and metals are used for tools, fuel, and construction.

3. 33 marks

   Where do the nutrients in soil actually come from, according to the chapter?

   Hint. Two distinct sources are named — one purely physical, one biological.

   ✦ Soil's nutrients like nitrogen and potassium, which plants need to grow, come from the slow breakdown of rocks and the remains of plants and animals — which means soil fertility depends on both a purely physical process (rock weathering) and a biological one (decomposition of dead organic matter).

4. 43 marks

   Define geodiversity, and explain how it creates habitats, according to the chapter.

   Hint. Geodiversity is defined as a variety PLUS the processes that keep changing that variety.

   ✦ 'There are various types of landforms, rocks, soils, etc., on Earth. This variety along with the processes that shape and alter them is called geodiversity.' The chapter states this variety 'helps create unique habitats where different types of life can thrive' — since different combinations of landform, rock and soil type each support different living conditions, more geological variety means more distinct habitats overall.

Solutions written by the tuition.in editorial team and checked against NCERT Curiosity — Textbook of Science for Grade 8, Chapter 13 (hecu113.pdf), Reprint 2026-27, pages 210-228. Questions are referenced from the NCERT textbook for identification.