Agriculture University Entrance Practice Set 1

Explanation: Rice has the largest area under cultivation among cereal crops in India, covering approximately 44 million hectares. India is the second largest producer of rice in the world after China.

Explanation: Laterite soils are formed in tropical and subtropical regions with high temperature and heavy rainfall. Intense leaching removes silica and bases, leaving behind iron and aluminium oxides that give these soils their characteristic red colour. They are found in the Western Ghats, eastern coast, and parts of northeast India.

Explanation: Trichogramma is a tiny wasp (egg parasitoid) that lays its eggs inside the eggs of lepidopteran pests (moths and butterflies), including stem borers, bollworms, and fruit borers. It is the most widely used biological control agent in agriculture worldwide.

Explanation: Sprinkler irrigation is most suitable for undulating (uneven) terrain where surface irrigation methods like flood or furrow irrigation cannot distribute water uniformly. The sprinkler system applies water through the air as spray, mimicking rainfall, and can be used on slopes.

Explanation: Rinderpest (cattle plague) was caused by the Rinderpest virus (Morbillivirus, family Paramyxoviridae). It was declared globally eradicated in 2011 by FAO and OIE — only the second disease (after smallpox) to be completely eradicated.

Explanation: Khaira disease of rice is caused by zinc deficiency. Symptoms include dusty brown spots on leaves, stunted growth, and delayed maturity. It is common in alkaline and calcareous soils where zinc availability is low. Application of zinc sulphate (ZnSO₄) at 25 kg/ha corrects the deficiency.

Explanation: Auxin, produced in the apical bud, inhibits the growth of lateral buds, a phenomenon known as apical dominance. When the apical bud is removed (decapitation), auxin supply decreases and lateral buds begin to grow, resulting in bushy plant growth.

Explanation: Nephridia are the excretory organs of annelids (segmented worms) such as earthworms. They filter waste products from the coelomic fluid and blood, functioning analogously to kidneys in vertebrates. Each segment typically has a pair of nephridia.

Explanation: Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during the pachytene stage of prophase I of meiosis. It results in genetic recombination and increases genetic variation in offspring.

Explanation: Norman Myers coined the term 'biodiversity hotspot' in 1988. A hotspot must have at least 1,500 endemic plant species and must have lost at least 70% of its primary vegetation. India has four hotspots: Western Ghats, Eastern Himalayas, Indo-Burma, and Sundaland.

Explanation: The ABO blood group system is determined by the presence of specific antigens (glycoproteins) on the surface of red blood cells. The gene has three alleles (IA, IB, and i) that determine which antigens are present, resulting in four blood groups: A, B, AB, and O.

Explanation: Kary Mullis developed the Polymerase Chain Reaction (PCR) technique in 1983 and was awarded the Nobel Prize in Chemistry in 1993. PCR allows amplification of specific DNA sequences in vitro using Taq polymerase (from Thermus aquaticus).

Explanation: Molarity (M) = moles of solute / volume of solution in litres. Moles of NaOH = 4/40 = 0.1 mol. Volume = 500 mL = 0.5 L. Molarity = 0.1/0.5 = 0.2 M.

Explanation: Among the halogen acids (HF, HCl, HBr, HI), HI is the strongest acid because the H–I bond is the weakest (largest atomic size of iodine) and dissociates most easily in water. Bond strength decreases down the group: HF > HCl > HBr > HI, but acid strength follows the opposite trend.

Explanation: Acetic acid (CH₃COOH) contains the carboxyl group (–COOH), which is the functional group characteristic of carboxylic acids. It consists of a carbonyl group (C=O) bonded to a hydroxyl group (–OH).

Explanation: The reaction of an alcohol with a carboxylic acid (in the presence of an acid catalyst like H₂SO₄) is called esterification. It produces an ester and water. For example, ethanol + acetic acid → ethyl acetate + water.

Explanation: Carbon (atomic number 6) has the electronic configuration 1s² 2s² 2p², giving it 4 valence electrons in its outermost shell (2s² 2p²). These 4 valence electrons enable carbon to form four covalent bonds.

Explanation: First convert 72 km/h to m/s: 72 × (1000/3600) = 20 m/s. Acceleration = (v − u)/t = (20 − 0)/10 = 2 m/s².

Explanation: Specific heat capacity is the heat required to raise the temperature of 1 kg of a substance by 1 K (or 1°C). Its SI unit is J/(kg·K), also written as J kg⁻¹ K⁻¹.

Explanation: Dispersion is the splitting of white light into its constituent colours (VIBGYOR) when it passes through a prism. This occurs because different wavelengths of light travel at different speeds in the glass, resulting in different angles of refraction.

Explanation: The magnetic field inside a long solenoid is uniform (constant in magnitude and direction) throughout the interior, directed along the axis. It is given by B = μ₀nI, where n is the number of turns per unit length and I is the current. Outside the solenoid, the field is negligibly small.

Explanation: Carbon-14 has a half-life of approximately 5,730 years. Radiocarbon dating is effective for organic materials up to about 50,000 years old. Beyond that, the remaining C-14 is too little to measure accurately.

Explanation: Since 8 = 2³, log₁₀ 8 = log₁₀ 2³ = 3 × log₁₀ 2 = 3 × 0.3010 = 0.9030.

Explanation: sin 30° = 1/2 and cos 60° = 1/2. Therefore, sin 30° + cos 60° = 1/2 + 1/2 = 1.

Explanation: Distance = √[(x₂−x₁)² + (y₂−y₁)²] = √[(5−2)² + (7−3)²] = √[9 + 16] = √25 = 5 units.

Explanation: The derivative of sin x with respect to x is cos x. This is one of the fundamental differentiation rules: d/dx(sin x) = cos x, derived from the limit definition of the derivative.

Explanation: To find the median, arrange the data in ascending order: {2, 3, 5, 7, 9}. Since there are 5 values (odd number), the median is the middle value, which is 5.

Explanation: Green manuring involves growing a leguminous crop (such as dhaincha, sunhemp, or sesbania) and ploughing it into the soil while still green. This adds organic matter and nitrogen (fixed by Rhizobium in root nodules) to improve soil fertility.

Explanation: 5C2 = 5! / (2! × 3!) = (5 × 4) / (2 × 1) = 20/2 = 10.

Explanation: After each half-life, half the substance remains. In 60 minutes there are 60/20 = 3 half-lives. Fraction remaining = (1/2)³ = 1/8.