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

Explanation

Methane (CH₄) is a potent greenhouse gas with a global warming potential over 25 times greater than carbon dioxide (CO₂) over a 100-year period. The primary sources of methane emissions can be categorized into natural and anthropogenic (human-caused) sources.

Option 1 is correct: Rice fields emit methane due to the anaerobic decomposition of organic matter in waterlogged conditions. This is a significant contributor to global methane emissions, particularly in rice-producing countries.

Option 2 is correct: Coal mining releases methane trapped within coal seams during the mining process. This is known as fugitive methane emissions and is a key source of industrial methane.

Option 3 is correct: Domestic animals, particularly ruminants like cattle and sheep, produce methane during enteric fermentation, a digestive process where microbes break down food in the stomach.

Option 4 is correct: Wetlands are natural sources of methane, produced through the anaerobic decomposition of organic material in water-saturated soils.

Explanation

Option (a) is incorrect: Passion flower plant is not an insectivorous plant. Passion flowers are flowering plants, typically known for their beautiful blooms and use in ornamental gardening.

Option (b) is correct: Pitcher plant is an insectivorous plant that derives nutrients by trapping and digesting insects. Its leaves are modified into pitcher-like structures containing digestive fluids. Insects are lured by the plant’s bright colors and nectar and are trapped when they fall into the pitcher. This adaptation helps the plant survive in nutrient-poor soils such as those lacking nitrogen.

Option (c) is incorrect: Night queen also known as Raat ki Rani, this is a type of flowering plant known for its fragrant flowers that bloom at night. It is not insectivorous.

Option (d) is incorrect: Flame of the forest is a flowering tree (also known as Butea monosperma), primarily used for its ornamental and medicinal properties, and is not an insectivorous plant.

Explanation

Probiotic foods are those that contain live microorganisms, typically bacteria or yeast, which confer health benefits to the host (usually humans) when consumed in adequate amounts. Common examples include sauerkraut, miso, tempeh, pickles, lassi, kombucha, and natto.

Statement 1 is correct: Probiotic food contains live beneficial bacteria, such as Lactobacillus and Bifidobacterium, which promote gut health. These bacteria are often present in fermented foods like yogurt, kimchi, and kefir.

Statement 2 is correct: Probiotic food plays a key role in maintaining a healthy gut flora by balancing the microorganisms in the digestive system. This is crucial for digestion, immune function, and preventing gastrointestinal disorders such as diarrhea and irritable bowel syndrome (IBS).

Explanation

In pitcher plants (Nepenthes) the leaf is modified into a pitcher-shaped structure that traps and digests insects. This adaptation helps the plant supplement its nutrient intake in poor soil conditions, such as those found in bogs or marshes. Pitcher plants are carnivorous in nature.The rim of the pitcher has nectar glands or patterns that attract insects. Once inside the insect faces slippery walls or downward-facing hairs that trap it. It falls into digestive fluid at the bottom where enzymes break it down. The plant absorbs the nutrients and thrives in nutrient-poorhabitats like bogs.

Explanation

Plant chlorophyll absorbs light most efficiently in the blue (around 430-450 nm) and red (around 640-680 nm) regions of the spectrum. These wavelengths drive the light-dependent reactions of photosynthesis, converting light energy into chemical energy. This energy is then used to convert carbon dioxide and water into glucose and oxygen. The absorption of blue light helps in the energy conversion, while red light plays a key role in the process of creating sugars. The green light is mostly reflected bach which is why plants appear green to us.

Explanation

Cellulose is a natural polysaccharide and the primary structural component of plant cell walls, providing strength and rigidity. It is widely used in industries for making paper, textiles, and derivatives like cellulose acetate and cellulose nitrate for various applications. Assertion (A) is true: Cellulose acetate, derived from cellulose, is used in the manufacture of shatterproof plastics, including glass used for eyewear and safety applications. These derivatives provide durability and impact resistance, essential for safety applications. Reason (R) is true: Polysaccharides such as cellulose are not soluble in water due to their extensive hydrogen bonding and crystalline structure. This insolubility is a key property of cellulose, which contributes to its stability and strength when used in manufacturing materials like shatterproof glass. Hence, Reason (R) provides the correct explanation of Assertion (A).

Explanation

Statement 1 is correct: Spirogyra and Ulothrix are types of blue green algae that can be found in both freshwater and marine environments. They are typically found in ponds, rivers, and even oceans in some cases. Spirogyra is known for its spiral-shaped chloroplasts and forms slimy green filaments/ mats on the water surface, especially when nutrients like nitrogen and phosphorus are abundant while Ulothrix is characterized by its simple, unbranched filaments and typically grows in both freshwater ponds and coastal regions. These algae play an important role in the aquatic food chain.

Statement 2 is correct: Chameleons have a unique ability to move their eyes independently of each other. They can focus one eye on an object in front while the other eye looks in a different direction, even behind them. This independent eye movement enables them to have a 360-degree view of their surroundings, aiding in predator detection and prey surveillance.

Explanation

Saturated fats are typically solid at room temperature and are found in animal products like butter, lard, and fatty cuts of meat, as well as some plant oils like coconut and palm oil. They are composed of fatty acids with no double bonds between carbon atoms, making them less reactive. Unsaturated fats are liquid at room temperature and are mainly found in plant-based oils (such as olive, sunflower, and canola oil) and fish. They contain one or more double bonds between carbon atoms which introduce "kinks" in the structure making them more reactive and beneficial for heart health when consumed in moderation. Assertion (A) is true: Unsaturated fats have at least one double bond between carbon atoms, making them more reactive. These double bonds are sites where chemical reactions can occur more easily compared to the single bonds in saturated fats. Reason (R) is false: Unsaturated fats contain at least one double bond in their carbon chain, not only single bonds. Saturated fats have only single bonds.

Explanation

Statement 1 is correct: Molasses is a thick, dark syrup that remains after the extraction of sugar from sugarcane or sugar beets. It is a common by-product in the sugar industry. It serves as a feedstock for producing synthetic chemical fertilizers and ethanol.

Statement 2 is correct: Bagasse, the fibrous residue left after extracting juice from sugarcane, is commonly used as a biofuel in the sugar industry to generate steam and electricity, making the process more energy-efficient.

Statement 3 is incorrect: Sugar is produced from various raw materials including sugarcane and sugar beets. Other sources for sugar production include sorghum and palm sap.

Explanation

Dichogamy refers to the condition in a bisexual flower where the male (androecium) and female (gynoecium) reproductive organs mature at different times to prevent self-pollination. This ensures cross-pollination between different plants or flowers which increases genetic diversity.