Living organisms primarily obtain the elements C, N, S, P, H, and O through plants and the food chain. Plants absorb these elements from the environment (air and soil) and convert them into organic compounds through processes like photosynthesis and the absorption of nutrients. Animals then obtain these elements by consuming plants or other animals, thus completing the cycle.
Here’s a more detailed look:
1. Carbon (C):
Plants:
Plants capture carbon dioxide from the atmosphere during photosynthesis and convert it into organic compounds like glucose.
Animals:
Animals obtain carbon by consuming plants or other animals that have consumed plants.
2. Nitrogen (N):
Plants: Plants absorb nitrogen from the soil in the form of nitrates or ammonia, according to the NCERT textbook. Some plants have symbiotic relationships with bacteria in their roots that help fix nitrogen from the atmosphere, as explained on the University of California, Berkeley website.
Animals: Animals obtain nitrogen by consuming plants or other animals.
3. Sulfur (S):
Plants: Plants absorb sulfur from the soil in the form of sulfate ions.
Animals: Animals obtain sulfur by consuming plants or other animals.
4. Phosphorus (P):
Plants: Plants absorb phosphorus from the soil in the form of phosphate ions.
Animals: Animals obtain phosphorus by consuming plants or other animals.
5. Hydrogen (H) and Oxygen (O):
Plants:
Plants use water (H₂O) during photosynthesis, and the hydrogen and oxygen atoms are incorporated into organic compounds.
Animals:
Animals obtain hydrogen and oxygen by consuming plants or other animals, and also through the intake of water and the respiration process.
In summary, the entry of C, N, S, P, H, and O into living forms is facilitated through the following:
Photosynthesis:
Plants convert atmospheric carbon dioxide and water into organic compounds, capturing these elements.
Absorption from soil:
Plants absorb nutrients like nitrogen, sulfur, and phosphorus from the soil.
Food chain:
The transfer of organic materials containing these elements from plants to animals and then to other consumers.
These processes ensure the continuous cycling of essential elements within ecosystems, supporting life on Earth.