CBSE Class 9 Science Flashcards

24 sample cards from the Science deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Name the natural resources that are essential physical resources for life and how each is purified naturally.

   Air, water, and soil. Air pollutants are dispersed/diluted by wind; water is purified by the water cycle and self-cleaning; soil is renewed by weathering and biological activity.

2. What is the major cause of air pollution from burning fossil fuels, and name two harmful oxides produced.

   Combustion of fossil fuels (coal, petroleum). Harmful oxides include oxides of nitrogen and sulphur (NOx and SO2), which cause acid rain, plus carbon dioxide and carbon monoxide.

3. What is acid rain and how is it formed?

   Acid rain is rain that is more acidic than normal, formed when oxides of sulphur and nitrogen dissolve in rain water to form sulphuric and nitric acids.

4. How is soil formed and what is soil erosion?

   Soil is formed over long periods by the breaking down (weathering) of rocks by sun, water, wind, and living organisms. Soil erosion is the removal of fertile topsoil by wind or flowing water.

5. What is humus and why is it important?

   Humus is the rotting dead organic matter (decayed plants/animals) in soil. It increases soil fertility, water-holding capacity, and provides nutrients.

6. Describe the water cycle.

   Water evaporates from water bodies and transpires from plants, condenses to form clouds, falls as precipitation (rain/snow), and returns to water bodies and groundwater, repeating the cycle.

7. Describe the carbon cycle.

   Carbon circulates among atmosphere, living organisms, and environment via photosynthesis (CO2 to organic carbon), respiration, decomposition, combustion of fuels, and dissolution in oceans (returning CO2 to the atmosphere).

8. Describe the nitrogen cycle, naming the key processes.

   Atmospheric nitrogen is converted to usable forms by nitrogen fixation (by Rhizobium bacteria and lightning), then nitrification, uptake by plants (assimilation), ammonification by decomposers, and returned to the atmosphere by denitrification.

9. Describe the oxygen cycle.

   Oxygen is released into the atmosphere by photosynthesis and is removed by respiration, combustion, and the formation of oxides; the atmosphere stays roughly balanced.

10. What is the greenhouse effect and which gases are responsible?

    The greenhouse effect is the trapping of heat by certain atmospheric gases, keeping Earth warm. Greenhouse gases include carbon dioxide, methane, and water vapour; their excess causes global warming.

11. What is the ozone layer and why is it important?

    The ozone layer (in the upper atmosphere) is made of O3 and shields Earth from harmful ultraviolet (UV) radiation from the Sun.

12. What are the two main sources of food for humans?

    Plants (agriculture - crops, fruits, vegetables) and animals (animal husbandry - milk, eggs, meat, fish).

13. Define crop, and distinguish between Kharif and Rabi crops.

    A crop is the same kind of plants grown and cultivated together at a place on a large scale. Kharif crops are grown in the rainy season (June-October), e.g., paddy, maize; Rabi crops are grown in winter (October-March), e.g., wheat, gram.

14. Name the macronutrients and micronutrients required by plants.

    Macronutrients (needed in large amounts): nitrogen, phosphorus, potassium, calcium, magnesium, sulphur. Micronutrients (needed in small amounts): iron, manganese, boron, zinc, copper, molybdenum, chlorine.

15. Distinguish between manure and fertilisers.

    Manure is natural organic matter (decomposed plant/animal waste) that adds humus and nutrients; fertilisers are commercially produced inorganic chemicals rich in specific nutrients (N, P, K) but add no humus.

16. What is crop rotation and how does mixed/intercropping differ?

    Crop rotation is growing different crops alternately on the same field to maintain soil fertility. Mixed cropping is growing two or more crops together; intercropping is growing them in a definite row pattern.

17. What are the three main methods of crop variety improvement?

    Hybridisation (crossing genetically different plants), selection, and introduction of genes (genetic modification) to obtain desired traits like higher yield and disease resistance.

18. Name the three main types of crop pests/storage losses and how stored grains are protected.

    Losses are caused by insects, rodents, and microorganisms (fungi/bacteria), plus moisture and temperature. Protection includes proper drying, fumigation, and storage in clean, dry, airtight conditions (e.g., silos, godowns).

19. What is animal husbandry?

    Animal husbandry is the scientific management of animal livestock, including feeding, breeding, shelter, and disease control, to obtain food and other products.

20. Distinguish between exotic, indigenous (desi), and cross-bred cattle.

    Indigenous (desi) breeds have good disease resistance; exotic/foreign breeds have long lactation periods and high milk yield; cross-breeds combine both traits (high yield plus resistance).

21. What are broilers and layers in poultry farming?

    Broilers are chickens raised for meat (fast growth, high feed efficiency); layers are hens raised for egg production.

22. What is composite fish culture?

    A system of fish farming in which several compatible fish species with different feeding habits are reared together in a single pond so all food zones of the pond are used efficiently.

23. Distinguish between capture fishing and culture fishery (aquaculture), and define mariculture.

    Capture fishing is obtaining fish from natural water bodies; culture fishery (aquaculture) is breeding and rearing fish in controlled conditions. Mariculture is the culture of marine fish in seawater.

24. What is apiculture and name a common bee variety used in India for high honey yield.

    Apiculture is the rearing of honeybees (bee-keeping) for honey and wax. Apis mellifera (Italian bee) is commonly used for high honey production.

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