Q1. Name two greenhouse gases.
Ans. Methane and CO2.
Q2. Name two chemicals that are depleting ozone layer?
Ans. Chlorofluorocarbons and compounds of chlorine and fluorine or halogen gases.
Q3. Name two gases released by fossil fuels and cause acid rain.
Ans. SO2 and NO2 which forms sulphurous acid and nitric acid.
Q4. Name types of soil?
Ans. Soil based on size of particles—sandy, clay.
Soil based on nutrient and nature—laterite soil, black soil, red soil, alluvial soil.
Q5. What is nitrification?
Ans. Conversion of free nitrogen present in atmosphere into compound of nitrogen i.e. nitrite and then nitrite to nitrates is called nitrification.
Q6. Name a nitrogen fixing bacteria.
Ans. Rhizobium bacteria.
Q7. State three methods by which free nitrogen can be converted into nitrates.
Ans. Biological fixation, lightning and industrial fixation.
Q8. Name four factors which lead to soil formation.
Ans. Sun, water, wind and living organisms.
Q9. What is humus?
Ans. The top most part of the soil which contains dead remains of plants and animal wastes like excreta, that adds nutrients to the soil.
Q10. What is soil erosion?
Ans. The topmost layer of soil that is loose, fertile and helps in the growth of vegetation gets carried away by wind and rain water is called soil erosion.
Q11. What is denitrification?
Ans. Conversion of nitrates into free nitrogen is called denitrification.
Q12. How does carbon exist in all life forms?
Ans. Carbon is present in all life forms in the form of proteins, carbohydrates, fats, nucleic acids and vitamins.
Q13. Name two biological important compounds of nitrogen.
Ans. Alkaloid, urea, DNA, RNA and proteins.
Q14. Name two elemental form of carbon.
Ans. Graphite and Diamond.
Q15. Name two combined forms of carbon.
Ans. CO2, carbonate and hydrogen carbonate.
Q16. Give two biotic components of the biosphere.
Ans. Plants and animals.
Q17. Name the free living nitrogen fixing bacteria.
Ans. Rhizopus bacteria
Q18. What is the role of photosynthesis in carbon cycle?
Ans. Photosynthesis helps in the intake of carbon dioxide and thereby reduces the percentage of carbon dioxide in the environment.
Q19. Name a chemical responsible for the depletion of ozone layer in the atmosphere.
Ans. CFC also known as chloro-fluro carbon.
Q20. What would happen if ozone layer in the atmosphere disappears?
Ans. The harmful radiations of UV light from sun will enter the earth’s biosphere and kill many living organisms.