Earth as a System: Energy, Matter, and Life
NCERT Class 9 Science • Chapter 13
Quick Answer
This Class 9 chapter views Earth as an interconnected system of spheres: the atmosphere, hydrosphere, lithosphere, and biosphere. It explains the flow of energy from the Sun, biogeochemical cycles of water, carbon, nitrogen, and oxygen, and how living things interact with their environment, highlighting the balance that sustains life.
↓ Free PDF, NCERT solutions, summary, key terms, FAQs below.
Read Online
Loading PDF…
Key Terms
- Biosphere
- The part of Earth where life exists, including all living organisms and the regions of land, water, and air they occupy.
- Atmosphere
- The layer of gases surrounding Earth that supports life, regulates temperature, and protects against harmful radiation.
- Hydrosphere
- All the water on Earth, including oceans, rivers, lakes, groundwater, and water vapour in the air.
- Lithosphere
- The solid outer layer of the Earth, consisting of the crust and rocky upper mantle, that provides land and minerals.
- Biogeochemical Cycle
- The continuous movement and recycling of elements such as carbon, nitrogen, oxygen, and water between living things and the environment.
- Water Cycle
- The continuous movement of water through evaporation, condensation, precipitation, and collection between the atmosphere, land, and oceans.
- Nitrogen Cycle
- The process by which nitrogen circulates between the atmosphere, soil, and living organisms through fixation, decomposition, and other steps.
Frequently Asked Questions
What are the main spheres of the Earth system?▾
The Earth system is made up of four interconnected spheres: the atmosphere (air), the hydrosphere (water), the lithosphere (land and rock), and the biosphere (living things). These spheres constantly interact and exchange energy and matter.
Why is the Sun important for the Earth system?▾
The Sun is the primary source of energy for Earth. Its energy drives the water cycle, weather, and climate, and it powers photosynthesis, which forms the base of nearly all food chains and supports life.
What is a biogeochemical cycle?▾
A biogeochemical cycle is the continuous recycling of elements such as carbon, nitrogen, oxygen, and water between living organisms and the non-living environment. These cycles keep essential materials available for life.
How does the water cycle work?▾
In the water cycle, the Sun's heat evaporates water from oceans and land into the air, where it condenses into clouds. The water then falls back as precipitation and collects in rivers, lakes, and oceans, repeating the cycle.
Why is the nitrogen cycle important?▾
Nitrogen is essential for proteins and DNA in living things, but most organisms cannot use atmospheric nitrogen directly. The nitrogen cycle converts it into usable forms through fixation and recycles it through soil, plants, animals, and decomposers.
How do living things interact with the Earth's spheres?▾
Living things in the biosphere depend on and influence the other spheres: they breathe air from the atmosphere, drink water from the hydrosphere, and obtain nutrients from the lithosphere. Their activities, in turn, shape these environments.
Disclaimer & Attribution
- All NCERT textbook PDFs displayed on this page are served directly from NCERT's official servers at ncert.nic.in. We do not host, store, or redistribute any PDF files on our servers.
- This website is free to use. We do not sell, charge for, or commercially exploit any NCERT content.
- All textbook content is the intellectual property of NCERT, Government of India and is published under their open-access policy for educational purposes.
- This page is provided purely for educational reference in compliance with NCERT's guidelines for non-commercial use of their freely available materials.