Question

Choose any one meal you ate recently (it could be anything, for example, roti and dal, rice and sambar, idli and chutney, and so on). For each main item in the meal, find out and explain: (i) how the carbon in it originally came from carbon dioxide in the air through photosynthesis, and (ii) how the nitrogen in it likely came from the atmosphere into the soil (for example, by bacteria or through the Haber-Bosch process and fertilisers) and then into the plant. Further, list other human activities involved in producing or cooking this meal that add extra carbon dioxide or nitrogen to the environment.

Answer 1

Meal Chosen: Roti and Dal

1. Roti (Wheat): 
   • Carbon: Wheat absorbs CO₂ from the air through photosynthesis and converts it into carbohydrates.
   • Nitrogen: Wheat absorbs nitrogen from the soil, supplied by nitrogen-fixing bacteria or fertilisers.
2. Dal (Pulses):
   • Carbon: Pulse plants absorb CO₂ through photosynthesis to prepare food.
   • Nitrogen: Rhizobium bacteria in root nodules fix atmospheric nitrogen, which plants use to make proteins.
3. Human Activities:
   • Farming and transportation release CO₂ through fuel burning.
   • Fertiliser production releases CO₂, while excess fertiliser use can cause nitrogen pollution.
   • Cooking with LPG releases CO₂.

Carbon enters food through photosynthesis, while nitrogen enters through soil nutrients and nitrogen fixation. Human activities add extra CO₂ and nitrogen compounds to the environment.