Biology (Part-I) (UPSC)

Total Questions: 50

21. Assertion (A): Unsaturated fats are more reactive compared with the saturated fats. [2003]

Reason (R): Unsaturated fats have only single bonds in their structure.

Correct Answer: (c) A is true but R is false
Solution:Assertion is true because unsaturated fats are more reactive compared with saturated fats due to multiple bonds present between carbon atoms. The reason is false because unsaturated fats have atleast double bond in their structure.

A saturated fat is a fat in which the fatty acids all have single bonds. An unsaturated fat is a fatty acid in which there is at least one double bond within the fatty acid chain.

22. Consider the following statements: [2003]

1. Molasses is a by-product of sugar production process.

2. Bagasse obtained in the sugar mills is used as a fuel in the boilers to generate steam for the sugar factories.

3. Sugar can only be produced from sugarcane as the raw material.

Which of these statements are correct?

Correct Answer: (a) 1 and 2
Solution:Molasses is by-product of sugar production process and bagasse of sugar used as a fuel in boilers for sugar factories. But sugar produced from sugar cane and also from sugar beet.
  • Sugarcane cultivation in India involves a series of well-defined stages, from land preparation to harvesting, and combines traditional practices with modern techniques.
  • Land preparation: Fields are deeply ploughed 2–3 times and leveled to make the soil loose and well-aerated. Proper drainage is ensured to avoid waterlogging, which is harmful to sugarcane roots.
  • Seed material selection: Healthy, disease-free cane sets are selected from approved varieties. Traditionally, 2–3 bud sets are used, requiring a large quantity of seed cane.
  • Bud chip settlings method: Single buds are removed from cane and raised in a nursery. These settlings are later transplanted into the main field, leading to substantial saving in seed material, uniform crop stand, and better germination.
  • Tissue culture planting: Sugarcane can also be cultivated using settlings prepared from tissue culture, which are genetically uniform and disease-free, resulting in higher yield and better sugar recovery.
  • Planting methods: Furrow method is most common in irrigated areas; trench and ring pit methods are used in high rainfall or water-scarce regions to improve moisture use and root growth.
  • Spacing and planting depth: Proper spacing allows better sunlight penetration, aeration, and nutrient absorption, leading to healthier crop growth.
  • Irrigation management: Sugarcane requires frequent irrigation, especially during tillering and elongation stages. Drip irrigation is increasingly adopted to save water and improve efficiency.
  • Nutrient management: Adequate application of organic manure, nitrogen, phosphorus, and potassium is essential for sustained growth and high yield.
  • Harvesting: The crop is harvested at full maturity when sugar content is highest, usually 10–18 months after planting, depending on the variety and season.

23. Assertion (A): Cellulose is used in making shatter-proof glass. [2006]

Reason (R): Polysaccharides are not soluble in water.

Correct Answer: (a) Both 'A' and 'R' are individually true and 'R' is the correct explanation of 'A' .
Solution:Cellulose is not soluble in water that is why it is used in making shatter-proof glass. Cellulose is a poly saccharide.

Glucose units make up the linear polymer (polysaccharide) known as cellulose. Plants typically produce it through synthesis.

The primary characteristics of this polysaccharide are biodegradability and hydrolysis resistance. Most plants contain this biopolymer, primarily in the leaves and stalks.
• It is the most abundant carbon input in soil. To access the glucose monomer, it must be cleaved by extracellular enzymes.
• These pieces are then transported into the cell for energy generation (catabolism) or production of biomass (anabolism).
• It is a biodegradable, chiral, tasteless compound without any odor.
• Cellulose is used by a diverse group of soil organisms including fungi such as Penicillium and Aspergillus and bacteria such as Streptomyces and Pseudomonas.
• Fungi and bacteria are important participants in the extracellular cleavage of the polysaccharide.
• Cotton fiber and wood are the principal industrial sources of polymer for industrial applications

24. Which one of the following parts of the pitcher plant becomes modified into a pitcher? [2007]

Correct Answer: (b) Leaf
Solution:In pitcher plant, the lamina of leaf is modified into pitcher and the leaf apex gives rise to a coloured lid for attracting the insects.
• Pitcher plants belong to family nepenthaceae. The members of the family are commonly known as ‘pitcher plants’ because their leaves bear jar-like structures.
• Distribution: Confined to the high rainfall hills and plateaus of north-eastern region, at altitudes ranging from 100–1500 m, particularly in Garo, Khasi and Jaintia hills of Meghalaya.

25. Which of the following types of light are strongly absorbed by plants? [2007]

Correct Answer: (b) Blue and red
Solution:Photosynthesis occurs between wavelengths of about 400 nm and 750 nm. Red and blue colour wavelength is categories in this wavelength. So, plants absorb these colours. Photosynthesis does not occur in the infra-red or in ultraviolet light.

26. Consider the following : [2008]

1. Rice fields

2. Coal mining

3. Domestic animals

4. Wet lands

Which of the above are sources of methane, a major greenhouse gas?

Correct Answer: (d) 1, 2, 3 and 4
Solution:Rice fields, coal mining, domestic animal and wet lands all are the sources of methane.
• Methane is the most important greenhouse gas after carbon dioxide.
• It is produced from decomposition of animal wastes and biological matter.
• The emission of this gas can be restricted by using animal wastes and biological matter to produce gobar gas (methane).

27. Which one of the following is an insectivorous plant? [2008]

Correct Answer: (b) Pitcher plant
Solution:

Insectivorous Plants
• These plants are specialized in trapping insects and are popularly known as insectivorous plants.
• They are very different from normal plants in their mode of nutrition. They, however, never prey upon humans or large animals.
• Insectivorous plants can broadly be divided into active and passive types based on their method of trapping their prey.
• The active ones can close their traps the moment insects land on them.
• The passive plants have a ‘pitfall’ mechanism, having some kind of jar or pitcher-like structure into which the insect slips and falls, to eventually be digested.
• The insectivorous plants often have several attractions such as brilliant colors, sweet secretions and other curios to lure their innocent victims.

28. Consider the following statements about probiotic food: [2008]

1. Probiotic food contains live bacteria which are considered beneficial to humans.

2. Probiotic food helps in maintaining gut flora.

Which of the statements given above is/are correct?

Correct Answer: (c) Both 1 and 2
Solution:Probiotics are the living microorganisms that are healthy for host organism. Lactic acid bacteria, Bifido bacteria are common type of microbes used as probiotics. Certain yeast and Bacilli may also useful. Probiotics are commonly consumed as a part of fermented food with specially added active live cultures such as yoghurt or as dietary supplements.

29. Consider the following statements: [2009]

1. Sweet orange plant is propagated by grafting technique.

2. Jasmine plant is propagated by layering technique.

Which of the statements given above is/are correct?

Correct Answer: (c) Both 1 and 2
Solution:Grafting is a most common method of vegetative propagation. In this method, parts of two plants are joined in such a way that they grow as a one plant. Sweet orange plant is propagated by grafting technique. Layering is another type of vegetative propagation. In this method, roots are artificially induced on the stem branches before they are detached from the plant for propagation. Jasmine plant is propagated by this technique.

30. In making the saffron spice, which one of the following parts of the plant is used? [2009]

Correct Answer: (d) Stigma
Solution:Saffron is a spice obtained from the stigma of the flower of Crocus sativus Linnaeus.
About Saffron Crop:
• It is one of the costliest herbal spices across the globe and popularly known as Red Gold or the Golden Condiment.
• The commercial part of Saffron is Stigma, which is the female part of flower also termed as Saffron filament or Saffron thread or Saffron stigmata.
• The seeds of Saffron are called corms or bulbs, and Saffron plant regenerates from the vegetative multiplication of its underground corms.
• It contains crocin, picrocrocin and saffranal which are very important constituents for both medicinal and aesthetic purposes.
• Distribution: The saffron plant is native to Greece Asia Minor, but it is now cultivated in many parts of Europe (especially Italy, France, and Spain), China, and India.
• In India around 90% of saffron production comes from Kashmir, where it has been grown for centuries.