Biology: Botany: UPSC Previous Year Questions (Science and Technology)

Explanation

The question evaluates the accuracy of botanical classifications for five plants: Cassava, Ginger, Malabar spinach, Mint, and Papaya. Key Definitions:

Woody shrub: A perennial plant with multiple woody stems branching from the base, typically under 6 m tall. Herb: A non-woody plant, often perennial or annual, with soft stems. Pseudostem: A false stem formed by tightly rolled leaf sheaths, not a true woody stem. Herbaceous climber: A non-woody plant that climbs or twines using support. Annual: Completes its life cycle in one year; perennial lives multiple years.

Pair 1 is correctly matched(Cassava - Woody Shrub):

Cassava (Manihot esculenta Crantz, Euphorbiaceae) is a tropical root crop from South America (Brazil, Paraguay). FAO and ScienceDirect classify it as a perennial woody shrub with tuberous roots (tapioca), grown as an annual. It reaches 1-3 m, with woody stems persisting in tropical climates.

Pair 2 is correctly matched(Ginger - Herb with Pseudostem):. Ginger (Zingiber officinale, Zingiberaceae) is a herbaceous perennial, grown as an annual for rhizomes. National Horticulture Board and ScienceDirect confirm its pseudostem (rolled leaf sheaths, 0.5-1.5 m) is not woody, distinguishing it from shrubs.

Pair 3 is correctly matched (Malabar Spinach - Herbaceous Climber): Malabar spinach (Basella alba/rubra, Basellaceae) is a fast-growing vine with soft, fleshy stems. ResearchGate, ICAR, and Missouri Botanical Garden classify it as a perennial herbaceous climber, twining on supports, grown as an annual in non-tropical areas.

Pair 4 is incorrectly matched (Mint - Annual Shrub): Mint (Mentha species, Lamiaceae) is a herbaceous perennial with soft, non-woody stems, spreading via runners. Indian Spices Board and Missouri Botanical Garden confirm it’s not an annual or shrub, regrowing from rhizomes yearly.

Pair 5 is incorrectly matched (Papaya - Woody Shrub): Papaya (Carica papaya, Caricaceae) is a tree-like herb or large herbaceous plant (3-10 m), with a single, hollow, fibrous stem, not woody. ICAR, ScienceDirect, and Missouri Botanical Garden classify it as a herbaceous perennial or small tree, short-lived (5-10 years), not a woody shrub.

Explanation

The carbon cycle is a natural process that involves the movement of carbon between the atmosphere, oceans, soil, rocks, and living organisms. Respiration, decay of organic matter, volcanic action, fossil fuel combustion, deforestation, ocean-atmosphere exchange adds carbon to the cycle. All living organisms (plants, animals, and microorganisms) respire and breaking down glucose and oxygen to release energy, CO₂, and water. This process adds carbon dioxide to the atmosphere. When dead plants, animals, and other organic materials decompose microbes break them down. During decomposition CO₂ and methane (CH₄) are released into the atmosphere. Volcanic eruptions release stored carbon dioxide from the Earth’s mantle into the atmosphere. This is a natural source of CO₂ emissions. During photosynthesis plants, algae, and some bacteria absorb CO₂ from the atmosphere and use sunlight to convert it into glucose and oxygen. This process removes carbon dioxide from the atmosphere rather than adding it.

Explanation

Maize is widely cultivated for the production of ethanol, which is used as a biofuel. Ethanol is derived from the fermentation of sugars and starches found in maize kernels. The United States and Brazil are among the largest producers of maize-based ethanol, which serves as a renewable energy source and an alternative to fossil fuels. Options (a), (c), and (d) are incorrect:

Jatropha is primarily cultivated for its seeds, which contain oil that can be converted into biodiesel. It is not used for ethanol production because it does not contain significant amounts of starch or sugars that can be fermented into ethanol. Pongamia (also known as Millettia pinnata) is an oilseed crop. Its seeds contain oil that are used popularly for biodiesel for biodiesel production, not ethanol. Sunflower is primarily grown for edible oil production, sunflower does not have the starch or sugar content necessary for ethanol production.

Explanation

Insectivorous plants like Venus flytraps and pitcher plants grow in nitrogen-poor, acidic, or waterlogged soils. They capture and digest insects to obtain essential nutrients such as nitrogen and phosphorus which are scarce in their environment. This adaptation allows them to thrive in nutrient-deficient habitats where other plants struggle. Though they perform photosynthesis but their carnivorous behavior supplements their nutritional needs which enables them to survive in challenging conditions.

Explanation

Mon 863 maize was genetically modified to produce a protein called Cry3Bb1 derived from the soil bacterium Bacillus thuringiensis (Bt). This protein is toxic to the corn rootworm which is a major pest that damages maize crops. By incorporating this trait, Mon 863 reduces the need for chemical pesticides and improves crop yields.

Explanation

Option (a) is correct: Statement 1 is correct:

Coffee plants (Coffea arabica and Coffea robusta) thrive in hot tropical climates with temperatures between 15°C and 28°C, high humidity, and well-distributed rainfall. They are typically grown in regions near the equator such as Brazil, Colombia, and Ethiopia. Tea plants (Camellia sinensis) can be grown in both tropical and subtropical regions. They prefer cooler climates with temperatures between 13°C and 30°C and require well-distributed rainfall. Tea is cultivated in countries like India (Assam, Darjeeling), China, and Kenya.

Statement 2 is incorrect: Coffee plants are more commonly propagated from seeds. Seeds are sown to produce seedlings, which are then transplanted to the field. This method ensures genetic diversity among coffee plants. Tea is propagated by both seeds and stem cuttings. The vegetative propagation (stem cuttings) is more common in commercial cultivation because it ensures uniformity in plant characteristics and quality. Differences between Coffee and Tea Cultivation:

Factor Coffee Tea Climate Warm, humid tropical climate Cool, humid subtropical/tropical climate Temperature 15°C - 30°C 13°C - 30°C Rainfall 1,500 - 2,500 mm (moderate) 1,500 - 3,000 mm (higher) Altitude 600 - 2,000 meters 150 - 2,000 meters Soil Type Well-drained, slightly acidic (pH 6-6.5), loamy or volcanic soil Deep, fertile, well-drained acidic soil (pH 4.5-5.5) Shade vs. Sunlight Prefers shade for humidity Prefers open sunlight Temperature Sensitivity Sensitive to frost and extreme heat More adaptable but sensitive to extreme cold Major Growing Regions (India) Karnataka, Kerala, Tamil Nadu (Western Ghats) Assam, West Bengal (Darjeeling), Tamil Nadu (Nilgiris), Kerala Harvesting Beans are handpicked, fermented, dried, and roasted Leaves are plucked, withered, oxidized (for black tea), and dried Processing Roasting required before consumption Processed into different types (green, black, white, oolong)

Explanation

Option 1 is correct: Crop rotation helps maintain soil fertility by alternating crops that deplete nutrients with those that replenish them. It also reduces soil erosion by providing continuous ground cover. Thus, it plays a crucial role in soil conservation and sustainable agriculture.

Option 2 is correct: Sand fences are barriers placed to prevent the movement of sand and reduce soil erosion in arid and semi-arid regions, such as Rajasthan.

Option 3 is correct: Terracing involves cutting steps into slopes to reduce water runoff and prevent soil erosion, particularly in hilly areas. It is widely practiced in regions like the Himalayas.

Option 4 is correct: Wind breaks are rows of trees or shrubs planted to block the wind, reducing wind erosion and protecting the topsoil in open areas.

Explanation

Statement 1 is correct: Pongamia pinnata, also known as the Indian beech tree, grows naturally in arid and semi-arid regions of India. It is highly drought-tolerant, making it a suitable biodiesel crop for areas with limited water availability.

Statement 2 is correct: The seeds of Pongamia pinnata are rich in lipid content(oleic acid) which is a key component in the production of biodiesel. The high oil yield from the seeds makes Pongamia a viable and sustainable biodiesel source. Recently, it has been used for ethanol production.

Explanation

Saffron spice is made from the stigma of the Crocus sativus flower, commonly known as the saffron crocus. The stigmas are handpicked, dried, and processed to produce saffron. Each flower has only three stigmas, making the harvesting process labor-intensive and contributing to saffron’s high value. The stigmas are highly prized for their distinctive flavor, aroma, and vibrant golden color.

Explanation

Statement 1 is correct: The sweet orange plant is propagated through the grafting technique where a scion (shoot) from a desired sweet orange tree is grafted onto the rootstock of a compatible plant. This ensures the plant retains the desired traits such as high fruit quality and disease resistance.

Statement 2 is correct: The jasmine plant is commonly propagated by layering technique, particularly mound layering or air layering. This method involves bending a healthy branch to the ground or wrapping it with moist materials to encourage root development, which helps maintain the plant’s genetic identity and growth potential.