General Q&A for Class 12 · Page 63
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What are two exotic varieties of cows?
Two prominent exotic cattle breeds are Holstein Friesian (or Holstein) and Jersey. Holstein Friesian cattle, originating from the Netherlands, are black and white spotted and are the world's highest milk-producing breed, yielding 25-30 liters daily. Jersey cattle, from the British Isle of Jersey, are smaller, fawn-colored animals producing milk with high butterfat content (5-6%), ideal for butter and cheese production. These
- GeneralClass 12All
What are two freshwater resources that provide water for human use?
Rivers and groundwater (aquifers) are the two primary freshwater sources that humans depend on for drinking water, agriculture, and industrial use. Rivers provide easily accessible surface water and have been the foundation for human civilization throughout history, supporting agriculture through irrigation and providing transportation routes. Groundwater, stored in underground aquifers, supplies approximately one-third of the world's population and is particularly crucial in
- GeneralClass 12All
What gases commonly cause air pollution?
Major air pollutants include carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxides (NOₓ), particulate matter (PM2.5 and PM10), ozone (O₃) at ground level, and volatile organic compounds (VOCs). Carbon monoxide, produced by incomplete combustion in vehicles and industrial processes, is particularly dangerous because it interferes with oxygen transport in the blood. Sulfur dioxide and nit
- GeneralClass 12All
What is the region of Earth's crust and atmosphere occupied by living organisms called?
This region is called the biosphere. The biosphere encompasses all areas of Earth where life exists, extending from the deepest ocean trenches (approximately 11 kilometers below sea level) to the upper atmosphere (roughly 10 kilometers above ground level). It includes portions of the lithosphere (Earth's crust and upper mantle), the hydrosphere (all water bodies), and the atmosphere (the air surrounding Earth). The biosphere is a relatively thin zone compared to Earth's total
- GeneralClass 12All
What is the oxygen content in Earth's atmosphere?
Earth's atmosphere contains approximately 21% oxygen (O₂) by volume, making it the second most abundant atmospheric gas after nitrogen (78%). This oxygen concentration is maintained through a delicate balance between oxygen-producing processes (primarily photosynthesis by plants, algae, and cyanobacteria) and oxygen-consuming processes (respiration, combustion, and oxidation reactions). The current oxygen level represents billions of years of biological evolution; early Earth
- GeneralClass 12All
What is the major atmospheric component of Mars and Venus?
Both Mars and Venus have atmospheres dominated by carbon dioxide (CO₂), comprising over 95% of each planet's atmospheric composition. Despite this similarity, the two planets have vastly different atmospheric conditions. Venus has an extremely dense atmosphere with surface pressures 90 times greater than Earth's, creating a runaway greenhouse effect with surface temperatures exceeding 450°C (850°F). Mars, conversely, has a very thin atmosphere with surface pressure le
- GeneralClass 12All
What is the direction of air movement in coastal areas during the day?
During daytime, air in coastal regions moves from the sea toward the land, creating what's called a sea breeze. This phenomenon occurs because land heats up much faster than water when exposed to sunlight. As the land surface warms, it heats the air above it, causing that air to become less dense and rise. This creates a low-pressure area over the land. Meanwhile, the air over the cooler ocean remains denser and at relatively higher pressure. Air naturally flows from high-pre
- GeneralClass 12All
What are the harmful effects of ultraviolet (UV) rays?
Ultraviolet rays can cause significant harm to both living organisms and the environment. For humans, prolonged UV exposure leads to sunburn, premature skin aging, and increases the risk of skin cancer, including melanoma. UV radiation also damages the eyes, potentially causing cataracts and other vision problems. Beyond human health, UV rays harm marine ecosystems by damaging phytoplankton, which forms the base of oceanic food chains. They also weaken plant immune systems, reduce crop yields
- GeneralClass 12All
Why does wind direction reverse in coastal areas at night?
At night, coastal winds reverse direction and blow from land to sea, creating a land breeze. This reversal occurs because land cools down much more rapidly than water after sunset. Water has a high specific heat capacity, meaning it retains heat longer, so the ocean remains relatively warm through the night. As the land surface cools, the air above it becomes denser and creates a high-pressure area. The ocean, still holding daytime heat, keeps the air above it warmer and at r
- GeneralClass 12All
What is the ultimate source of energy in an ecosystem?
The sun is the ultimate source of energy for nearly all ecosystems on Earth. Through the process of photosynthesis, plants and other autotrophs convert solar energy into chemical energy stored in organic compounds like glucose. This energy then flows through the ecosystem as herbivores consume plants, carnivores eat herbivores, and decomposers break down dead organic matter. Solar energy drives not only biological processes but also weather patterns, ocean currents, and the w
- GeneralClass 12All
What are the main substances involved in biogeochemical cycles?
Biogeochemical cycles primarily involve essential elements and compounds that move through Earth's living and non-living systems. The main substances include carbon (cycling through the atmosphere as CO₂, in living organisms, and in geological formations), nitrogen (moving between atmospheric N₂, soil compounds, and living tissues), oxygen (exchanged through respiration and photosynthesis), phosphorus (cycling through rocks,
- GeneralClass 12All
What are two major greenhouse gases in Earth's atmosphere?
The two most significant greenhouse gases are carbon dioxide (CO₂) and methane (CH₄). Carbon dioxide is released primarily through burning fossil fuels, deforestation, and natural processes like respiration and volcanic activity. While CO₂ has a lower warming potential per molecule, its abundance and long atmospheric lifetime make it the primary driver of climate change. Methane, though present in smaller quantities, is approximately 25 times more effective a
- GeneralClass 12All
Which crop can tolerate waterlogging in fields?
Rice (paddy) is the primary crop that tolerates waterlogging and is actually grown in flooded conditions. Rice plants have specialized tissues called aerenchyma that allow oxygen transport from leaves to submerged roots, enabling survival in waterlogged fields. Other crops with some waterlogging tolerance include sugarcane, jute, and certain varieties of taro. However, most crops suffer from waterlogging as it reduces oxygen availability to roots, causing root damage and redu
- GeneralClass 12All
What are the hazards of using fertilizers?
Fertilizer hazards include environmental pollution through nutrient runoff causing water eutrophication, soil degradation from reduced organic matter and beneficial microorganisms, groundwater contamination with nitrates affecting drinking water quality, health risks from chemical residues in food, economic burden on farmers due to increasing costs, and disruption of soil nutrient balance lea
- GeneralClass 12All
What has been one disadvantage of the Green Revolution?
A major disadvantage of the Green Revolution has been increased dependence on chemical inputs and environmental degradation. While it significantly increased food production, the Green Revolution promoted intensive use of chemical fertilizers, pesticides, and high-yielding varieties requiring substantial water. This led to soil degradation, water table depletion, loss of biodiversity, pest resistance, and health concerns. Additionally, it created economic disparities as small
- GeneralClass 12All
What is crop breeding between different species of the same genus called?
This is called interspecific hybridization or wide hybridization. It involves crossing two different species within the same genus to combine desirable traits from both parents. For example, crossing different species of Brassica or Triticum (wheat) creates new varieties with improved characteristics like disease resistance, higher yield, or better adaptability. This technique is more challenging than breeding within the same species but can
- GeneralClass 12All
In what type of areas is the river lift system more applicable?
The river lift system is most applicable in areas where river water levels are lower than the surrounding agricultural fields and in regions with perennial or seasonal rivers flowing through or near cultivable land. This system is particularly useful in areas lacking adequate rainfall or groundwater resources. It's commonly employed in riverine plains and areas with undulating terrain where gravity-flow irrigation is not feasible, providing a reliable irrigat
- GeneralClass 12All
What does the term livestock mean?
Livestock refers to domesticated animals raised in agricultural settings for productive purposes. This includes cattle, buffalo, sheep, goats, pigs, horses, and poultry kept for various products and services. Livestock provide food products (milk, meat, eggs), materials (wool, leather, hides), labor (draft animals for plowing and transport), and manure for fertilization. Livestock farming is integral to agriculture, providing income, nutrition, and supporting livelihoods for
- GeneralClass 12All
What are two cropping patterns where multiple crops are cultivated together?
The two main cropping patterns are mixed cropping and intercropping. Mixed cropping involves growing two or more crops simultaneously on the same field without distinct row arrangements, such as wheat and gram or groundnut and sunflower grown together. Intercropping is growing two or more crops simultaneously in definite row patterns, like maize and soybean in alternate rows. Both practices maximize land use, reduce pest risk
- GeneralClass 12All
What is the major disadvantage of using fertilizers?
The major disadvantage of using chemical fertilizers is environmental pollution and soil degradation. Excessive fertilizer use leads to nutrient runoff into water bodies, causing eutrophication where algae blooms deplete oxygen and harm aquatic life. Over-reliance on fertilizers can reduce soil organic matter, disrupt beneficial soil microorganisms, and cause soil acidification. Long-term use may also lead to nutrient imbalances, reduced soil fertility, and groundwater contam