UPSC 2008 Science and Technology Questions with Answers

Explanation

Bisphenol A (BPA) is an industrial chemical extensively used in the production of polycarbonate plastics and epoxy resins. Polycarbonate plastics made using BPA are commonly employed in the manufacture of reusable water bottles, food containers, and baby bottles due to their durability and lightweight properties. Epoxy resins containing BPA are used as coatings for the inside of food and beverage cans to prevent corrosion and contamination. However, BPA is a controversial substance because it can leach into food and beverages under high temperatures or prolonged storage. It is considered a potential endocrine disruptor that may interfere with hormonal activity, prompting regulatory bodies worldwide to evaluate its safety in food-related applications.

Explanation

Methane and air are responsible for mine explosions, often referred to as fire damp explosions. Methane (CH₄) is a flammable gas that accumulates in coal mines. When mixed with air in the presence of a spark, it can cause deadly explosions. Options (a), (b) and (d) are incorrect:

While Hydrogen and Oxygen are explosive, these gases are not significantly common in mining environments. Oxygen and Acetylene are used in welding, not relevant to mine explosions. Carbon Dioxide and Methane: Carbon dioxide is inert and cannot contribute to mine explosions.

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

The intriguing phenomenon of sexual cannibalism, where the female kills the male after copulation, is observed in some species of spiders. In certain species like the Australian redback spider and the black widow, the female spider consumes the male after mating.

Option (a), (b) and (d) are incorrect:

Dragonflies do not exhibit sexual cannibalism in the same way spiders do. While females may sometimes be aggressive toward males, they do not typically kill them after copulation. In honeybees, the male (drone) dies after mating, but this is not due to the female killing him. After mating, the drone’s genitalia are ripped off during copulation, leading to death. Pit vipers, such as rattlesnakes, do not exhibit sexual cannibalism. After mating, the male and female go separate ways. There is no phenomenon where the female kills the male after copulation.

Explanation

The king cobra (Ophiophagus hannah) is a snake whose diet primarily consists of other snakes, including venomous species such as kraits, pythons, and even other cobras. The name "Ophiophagus" literally means "snake-eater." King Cobras are solitary creatures and are primarily active during the day (diurnal). King Cobras are found in forests, grasslands, and hilly terrains across South and Southeast Asia. The King Cobra is the longest venomous snake in the world, growing up to 5.6 meters (18.5 feet).

Explanation

The pH level of blood in a normal person typically ranges from 7.35 to 7.45. This is considered slightly alkaline and is crucial for maintaining the proper function of enzymes and other biochemical processes in the body. The normal pH range of blood is tightly regulated by the body through mechanisms like buffer systems (such as the bicarbonate buffer system) to prevent drastic shifts in pH that could be harmful. A pH below 7.35 is considered acidosis, while a pH above 7.45 is considered alkalosis. Both conditions can disrupt normal physiological processes. The body maintains this narrow pH range to ensure optimal conditions for enzyme activity, oxygen transport, and metabolic reactions.

Explanation

Assertion (A) is true: The liver plays a crucial role in the digestion of fats. The liver’s primary role is to produce bile, which is essential for the digestion and absorption of fats. Bile is stored in the gallbladder and released into the small intestine when fat is detected in the stomach. Bile emulsifies fats by breaking them down into smaller droplets. This makes it easier for digestive enzymes, primarily lipase from the pancreas, to act on the fats and break them down further. Reason (R) is false: The liver does not produce fat-digesting enzymes. The production of fat-digesting enzymes occurs in the pancreas, not the liver. Lipase enzyme is secreted by the pancreas and is responsible for breaking down triglycerides (fats) into glycerol and fatty acids. Lipase works on the small fat droplets that have been emulsified by bile.

Explanation

Option (a) is correct:

The echidna is a monotreme, a group of egg-laying mammals that includes the platypus and echidna. Unlike most mammals, monotremes do not give birth to live young. They lay eggs and after laying eggs, the female echidna incubates them in a special pouch-like structure on her abdomen. Once the eggs hatch, the mother nurses her young by secreting milk from mammary glands, though monotremes do not have nipples. The milk oozes through the skin and the young lap it up.They are found in Australia and New Guinea and are adapted to a variety of environments, including forests and deserts. Options (b), (c) and (d) are incorrect:

Kangaroos are marsupials, meaning they give birth to live young that are underdeveloped at birth. The baby, called a joey, continues to develop in the mother’s pouch. Porcupines are placental mammals and they give birth to live young. These mammals develop their young inside the mother’s body before birth. Whales are placental mammals and give birth to live young after a long gestation period.