UPSC 2014 Science and Technology Questions with Answers

Explanation

The animal kingdom is broadly classified into different phyla based on structural and functional characteristics.

Option (a) is correct: Arthropoda is the largest phylum in the animal kingdom, including organisms with jointed appendages, segmented bodies, and exoskeletons made of chitin. The phylum is further divided into several subphyla, two of which are:

Chelicerata (includes arachnids like mites, spiders, and scorpions) and Crustacea (includes crabs and other aquatic arthropods). The subphylum Chelicerata (e.g., spiders, scorpions) has two body regions, no antennae, four pairs of legs, and uses chelicerae for feeding, adapted to terrestrial life with book lungs. Crustacea (e.g., crabs, lobsters) has three body regions, two pairs of antennae, gills for respiration, and compound eyes, primarily adapted to aquatic habitats with specialized mandibles. Hence, the crab does not belong to the same class as the mite, spider, and scorpion.

Explanation

A food chain represents the transfer of energy through a series of organisms, starting from green plants (primary producers) and progressing through successive consumers. For example: Grasses Grasshopper Frog Snake Hawk/ Eagle. Each step in the food chain is referred to as a trophic level, indicating the organism’s position in the chain. Food chains begin with producers and end with top carnivores. In marine ecosystems, phytoplankton serve as primary producers. These include:

Diatoms (unicellular algae) Coccolithophores (unicellular eukaryotic protists), Cyanobacteria (blue-green algae such as Synechococcus, Prochlorococcus, Nostoc, and Spirogyra) Dinoflagellates (flagellated protists) Crustaceans, a group of arthropods that includes crabs, lobsters, shrimp, krill, and barnacles, feed on diatoms. In turn, herrings, a type of fish, consume crustaceans, completing this segment of the marine food chain.

Explanation

Statement 1 is correct: PV technology directly converts sunlight into electricity using semiconductor materials like silicon. When sunlight hits the PV cells, it excites electrons, generating Direct Current (DC) electricity. This is a clean and efficient method of harnessing solar energy for electricity. Solar thermal systems use solar collectors to capture the Sun’s heat. This heat is typically used to produce steam, which drives turbines connected to generators, producing electricity. Solar thermal is often used in large-scale power plants and heating systems.

Statement 2 is incorrect: PV systems initially produce Direct Current (DC), which is then converted to Alternating Current (AC) using inverters for compatibility with the electrical grid and household appliances. Solar Thermal systems generate heat, which is used to produce AC electricity through conventional turbines and generators.

Statement 3 is incorrect: India has established manufacturing capabilities for both Solar Thermal and Photovoltaic technologies. The country is expanding its PV manufacturing capacity, aiming to become self-sufficient and reduce reliance on imports.

Explanation

Hibernation is a survival strategy employed by various animals to endure periods of reduced food availability and harsh environmental conditions, typically during winter. This state is characterized by significantly lowered metabolic rates, decreased body temperatures, and reduced physiological activities. Many bat species enter hibernation during colder months when their insect prey becomes scarce. During hibernation, bats can experience a substantial drop in body temperature and significant reduction in metabolic rate. They often hibernate communally in caves, mines, or other sheltered locations that provide stable, cold environments. Bears undergo a form of hibernation known as torpor, which is less extreme than the hibernation observed in smaller mammals. During torpor, bears experience a moderate decrease in body temperature and metabolic rate. They remain in dens throughout the winter months, surviving on stored body fat. Notably, female bears give birth during this period and are capable of nursing their cubs without leaving the den. Species such as ground squirrels and certain mice enter deep hibernation during which they significantly lower their body temperatures and metabolic rates. This state allows them to conserve energy and survive extended periods without food. Rodents often prepare for hibernation by accumulating fat reserves and creating insulated nests or burrows to protect against the cold.

Explanation

The carbon cycle is a biogeochemical process where carbon atoms continuously move between the atmosphere, oceans, soil, and living organisms through processes like photosynthesis, respiration, decomposition, and combustion. Through photosynthesis, plants absorb atmospheric CO₂ to produce glucose, while animals release CO₂ through respiration, and when organisms die, decomposition returns their carbon to the soil and atmosphere, completing this vital planetary cycle.

Statement 1 is correct: Volcanic eruptions release CO₂ stored in Earth’s mantle into the atmosphere, contributing to the carbon cycle.

Statement 2 is correct: Respiration is the process by which organisms, including plants and animals, convert organic compounds into energy, producing CO₂ as a byproduct. This CO₂ is then released into the atmosphere.

Statement 3 is incorrect: Photosynthesis is the process by which green plants, algae, and some bacteria absorb CO₂ from the atmosphere and, using sunlight, convert it into glucose and oxygen. This process removes CO₂ from the atmosphere.

Statement 4 is correct: When organisms die, decomposers like bacteria and fungi break down their organic matter, resulting in the release of CO₂ back into the atmosphere through the process of decomposition.

Explanation

Ecological succession is the process of change in the species structure of an ecological community over time. Types of Succession:

Primary Succession occurs on newly formed or exposed land where no previous life existed (e.g., bare rock, lava flows). Pioneer species like lichens and mosses initiate the process, gradually leading to the development of soil and a stable ecosystem. Secondary Succession happens in areas where an ecosystem previously existed but was disturbed (e.g., after a forest fire or flood). Soil is already present, and recovery occurs more quickly than in primary succession.

Option (b) is correct: Lichens are among the first organisms to colonize bare rock or barren environments, breaking down minerals to create soil and paving the way for other plants and organisms. They are unique composite organisms resulting from a symbiotic association between a fungus and a photosynthetic partner, which can be either green algae or cyanobacteria. In this partnership, the fungal component, known as the mycobiont, provides structure and protection, while the photosynthetic partner, referred to as the photobiont, contributes nutrients through photosynthesis.