Crop variety, nutrients, irrigation, animal husbandry MCQs

Q1. Which of the following correctly pairs a plant nutrient with the source from which the plant primarily obtains it?

• A.Carbon and oxygen - from air; hydrogen - from water; mineral elements - from soil
• B.Carbon and oxygen - from soil only; hydrogen - from the air
• C.Nitrogen - directly from atmospheric N2 by all plants without microbial help
• D.Phosphorus and potassium - from atmospheric air

Answer: A. Carbon and oxygen - from air; hydrogen - from water; mineral elements - from soil

That leaves only option A). Confirm with the chapter rule: Plants obtain carbon and oxygen from atmospheric CO2 and O2 during photosynthesis and respiration. Hydrogen comes from soil water taken up by roots. The 13 essential mineral nutrients (N, P, K, Ca, Mg, S, Fe, Zn, Cu, Mn, Mo, B, Cl) are absorbed from the soil. Most plants cannot fix atmospheric N2 directly - they depend on the nitrogen cycle and microbes. Hence only option (a) is correct (biology, chapter 'Improvement in Food Resources'). Answer: A) Carbon and oxygen - from air; hydrogen - from water; mineral elements - from soil.

Q2. Which of the following is the BEST single description of the goal of animal husbandry in agriculture?

• A.Scientific management of livestock for milk, meat, eggs, wool, honey, silk and draft power, ensuring animal welfare
• B.Hunting wild animals from forests with no plan for breeding or care
• C.Removing all animals from the agricultural system to grow only crops
• D.Using only one species of cattle regardless of region or purpose

Answer: A. Scientific management of livestock for milk, meat, eggs, wool, honey, silk and draft power, ensuring animal welfare

Going back to the NCERT chapter, Animal husbandry is the scientific management of farm animals - cattle, buffalo, poultry, fish, bees, silkworm - to obtain products like milk, meat, eggs, wool, honey, silk and draft work, while caring for the animals' health and welfare. The other options misrepresent its scope. Hence option (a). Hence the answer is A) Scientific management of livestock for milk, meat, eggs, wool, honey, silk and draft power, ensuring animal welfare.

Q3. Which of the following pairings of pest and its biocontrol/management practice is INCORRECT?

• A.Locust swarms - use of mosquito nets in homes
• B.Plant insect pests - release of natural predators like ladybird beetles
• C.Mosquitoes (vectors of human disease) - biological larvicides such as Bacillus thuringiensis israelensis
• D.Crop diseases - sowing of disease-resistant varieties

Answer: A. Locust swarms - use of mosquito nets in homes

Textbook fact: Locust swarms damage crops over vast areas and are controlled by spraying or organised swarm-fighting; mosquito nets in homes are irrelevant to locust management. The other three pairings - predator beetles, BTi larvicides and resistant varieties - are correct biocontrol/management practices. Hence option (a) is incorrect. Therefore the correct option is A) Locust swarms - use of mosquito nets in homes.