General Q&A for Class 12 · Page 235
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Explain the various harmful effects of fertilizers.
Excessive or improper fertilizer use creates significant environmental, ecological, and agricultural problems that can undermine the very productivity gains they're meant to provide. Soil health degradation occurs when farmers rely exclusively on chemical fertilizers while neglecting organic matter addition—this gradually depletes soil carbon, destroys soil structure, reduces beneficial microbial populations, and diminishes the soil's natural fertility. Over years, such
- GeneralClass 12All
What are the advantages of manure and fertilizers?
Manure and fertilizers serve complementary roles in maintaining and enhancing soil fertility, each offering distinct advantages that together form the foundation of productive agriculture. Organic manure—composed of decomposed animal waste, crop residues, and other biological materials—provides multiple benefits beyond simple nutrient supply. It improves soil structure by increasing organic matter content, which enhances water retention in sandy soils and drainage
- GeneralClass 12All
What is meant by 'sowing'? What are the various methods of sowing the seeds?
Sowing is the agricultural practice of placing seeds in soil at appropriate depths, spacing, and timing to ensure optimal germination and establishment of crops. This seemingly simple operation is actually a critical determinant of crop success because proper sowing influences seed-soil contact, moisture availability, emergence uniformity, and the crop's ability to compete with weeds while maximizing sunlight and nutrient capture. The depth of sowing varies by seed size (small seeds like must
- GeneralClass 12All
What is irrigation? Why is irrigation necessary
Irrigation is the artificial application of water to agricultural land to supplement natural rainfall and ensure adequate soil moisture for crop growth throughout the growing season. It involves various methods—from traditional flooding and furrow systems to modern drip and sprinkler technologies—designed to deliver water at the right time, in the right quantity, and with minimal waste. Unlike rainfed agriculture that depends entirely on uncertain monsoon patterns, irrigation prov
- GeneralClass 12All
What are good quality seeds? You are given a sample of wheat seeds. How will you select good, healthy seeds for sowing?
Good quality seeds possess specific characteristics that directly impact germination rates, crop vigor, and ultimately yield. High-quality seeds demonstrate high genetic purity (true to variety), physical purity (free from other crop seeds, weed seeds, and inert matter), excellent viability (germination percentage typically above 85-90%), and vigor (ability to establish quickly even under less-than-ideal conditions). They should be well-developed, uniform in size, undamaged, free from disease
- GeneralClass 12All
Write the correct sequence of steps undertaken for farming.
The farming process follows a systematic sequence that begins well before seeds touch the soil and continues through post-harvest handling. The cycle starts with soil preparation (tilling/ploughing), which loosens compacted earth, improves aeration, brings nutrients to the surface, and facilitates root penetration. This is followed by leveling the field to ensure uniform water distribution and prevent waterlogging in low spots. Next comes sowing</stro
- GeneralClass 12All
Name the implements which are used for the following agricultural practices.
(a) Tilling of the soil: Traditional ploughs (wooden or iron), cultivators, and harrows are the primary implements for tilling. In modern mechanized farming, tractors with mounted disc ploughs or rotavators break up and turn the soil efficiently, while bullock-drawn indigenous ploughs remain common in small-scale operations across India. (b) Sowing of the seeds: Seed drills and seed-cum-fertilizer drills enable precise placement and spacing of seeds a
- GeneralClass 12All
Explain the factors which are responsible for loss of grain during storage.
Grain storage losses occur due to a combination of biological, environmental, and physical factors that can significantly reduce both the quantity and quality of stored produce. The primary biological threats include insect pests like weevils, grain borers, and moths that feed on stored grains, as well as rodents such as rats and mice that consume and contaminate large quantities. Fungal growth, particularly molds, develops when moisture content exceeds safe levels (typically above 12-14% for
- GeneralClass 12All
Write down the steps of the TCA (Krebs) Cycle.
The Krebs cycle proceeds through nine enzymatic steps in the mitochondrial matrix: Step Reactant → Product Enzyme Cofactor/Output 1 Acetyl CoA + OAA + H₂O → Citric
- GeneralClass 12All
. Draw the diagram of the mitochondrial Electron Transport System (ETS).
[Intermembrane Space] ← 2H⁺ ← [Matrix] ↓ [NADH + H⁺] ↓ [Complex I: NADH Dehydrogenase] → NAD⁺ ↓ [Ubiquinone (CoQ)] ↓ [Complex II: Succinate Dehydrogenase] ← FADH₂ → FAD ↓ [Ubiquinol (Reduced CoQ)] ↓ [Complex III: Cytochrome bc₁] ↓ [Cytochrome c] (mobile carrier) ↓ [Complex IV: Cytochrome c Oxidase (a, a
- GeneralClass 12All
Plants can survive without respiratory organs. Give reasons.
(i) Decentralized respiration: Each plant part (root, stem, leaf) performs its own gas exchange with minimal inter-organ transport. (ii) Low metabolic rate: Plants have significantly lower oxygen demands compared to animals, except during photosynthesis when leaves utilize O₂ produced internally. (iii) Short diffusion distances: Living cells in plants are located close to the surface or have ac
- GeneralClass 12All
Though fats yield more kilocalories per gram than carbohydrates, they have a lower RQ. Explain.
Energy yield: Fats: 9 kcal/g Carbohydrates: 4 kcal/g Respiratory Quotient (RQ): For carbohydrates: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O RQ = 6CO₂ / 6O₂ = 1 For fats (Tripalmitin): 2(C₅₁H₉₈O₆) + 145O₂ → 102CO₂ + 98H₂O RQ = 102 / 145 = 0.7
- GeneralClass 12All
How do red muscle fibers in animals work for longer periods without fatigue?
Answer: Red muscle fibers contain: Myoglobin: A respiratory pigment that stores and transports large amounts of oxygen. High mitochondrial density: Enables sustained aerobic respiration. Slow ATP hydrolysis rate: Conserves energy. Rich capillary network: Ensures continuous oxygen supply. These adaptations make red fibers <st
- GeneralClass 12All
Tree trunks do not have stomata. How do they respire, given that plants lack respiratory organs?
(i) In woody stems, living cells are organized in thin layers beneath the bark.(ii) Gas exchange occurs through lenticels—small pores in the bark.(iii)Parenchyma cells are loosely arranged, providing an interconnected network of air spaces for efficient gas diffusion. Thus, even without stomata or specialized respiratory organs, trees can respire effectively.
- GeneralClass 12All
. Which process of respiration is more efficient—aerobic or anaerobic? Explain with equations.
Type ATP Yield Efficiency Aerobic respiration 36–38 ATP High Anaerobic respiration
- GeneralClass 12All
Human beings are highly evolved species, yet they may undergo anaerobic respiration. Explain.
During vigorous exercise, oxygen supply to skeletal muscles becomes insufficient. Under these conditions, muscle cells switch to lactic acid fermentation instead of aerobic respiration. Reaction: CH₃COCOOH (Pyruvate) → CH₃CHOHCOOH (Lactic acid) + Energy Enzyme: Lactic acid dehydrogenase This process allows muscles to continue producing ATP temporarily, though lactic
- GeneralClass 12All
Anaerobic respiration has an infinite RQ value. Why?
Respiratory Quotient (RQ) is defined as: RQ = Volume of CO₂ evolved / Volume of O₂ consumed In anaerobic respiration (fermentation), no oxygen is consumed (O₂ = 0), but CO₂ is still released. Example (Alcoholic fermentation): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ RQ = 2CO₂ / 0O₂ = ∞ Hence, RQ is theoretically infinite in anaerobic
- GeneralClass 12All
Though we say that aerobic respiration uses oxygen, none of the pathways (glycolysis, Krebs cycle) directly utilize it. Where is oxygen used?
Oxygen acts as the terminal electron acceptor in the Electron Transport System (ETS). At the end of the chain, oxygen combines with electrons and protons (H⁺) to form water (H₂O). Reaction: ½O₂ + 2H⁺ + 2e⁻ → H₂O This step is crucial; without oxygen, the entire ETS halts, and aerobic respiration cannot proceed.
- GeneralClass 12All
Name the complex associated with F₀–F₁ in mitochondria. How many ATP molecules are produced when one NADH is oxidized? What is the role of F₀–F₁?
Complex V (ATP synthase) is associated with the F₀–F₁ particle, also called oxysome or elementary particle. ATP yield: Oxidation of 1 NADH produces approximately 3 ATP molecules. F₀ part: Acts as a proton tunnel, allowing H⁺ ions to flow from the intermembrane space into the mitochondrial matrix. F₁ part:</stro
- GeneralClass 12All
Define glycolysis. Where does it occur?
Answer: Glycolysis is the enzymatic breakdown of one molecule of glucose (6-carbon) into two molecules of pyruvic acid (3-carbon each). It occurs in the cytoplasm of the cell and does not require oxygen, making it common to both aerobic and anaerobic respiration. Key features: Net gain: 2 ATP, 2 NADH + H⁺ Location: Cytoplasm <