General Q&A for Class 12 · Page 232
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What is global warming? Name the gas which is responsible for causing global warming?
Global warming refers to the long-term increase in Earth's average surface temperature due to human activities that increase atmospheric concentrations of heat-trapping gases. Since the late 19th century, global average temperatures have risen by approximately 1.1°C, with accelerating warming in recent decades. This phenomenon disrupts climate patterns worldwide, causing melting polar ice caps and glaciers, rising sea levels, more frequent and intense heatwaves, altered precipitation patt
- GeneralClass 12All
How deforestation and decreased rainfall are related?
Deforestation directly causes decreased rainfall in affected regions through disruption of the water cycle, creating a feedback loop that can transform forested areas into drier landscapes. Trees play a crucial role in rainfall generation through transpiration—the process where tree roots absorb groundwater and release water vapor through leaf pores into the atmosphere. A single large tree can transpire hundreds of liters of water daily, and forests collectively pump massive amounts of
- GeneralClass 12All
What is the significance of Red Data Book?
The Red Data Book holds immense significance as the global standard for assessing and documenting the conservation status of species facing extinction risk. Maintained by the International Union for Conservation of Nature (IUCN), it provides scientifically rigorous assessments that categorize thousands of plant and animal species based on their vulnerability to extinction. This standardized classification system enables governments, conservation organizations, researchers, and policymakers wo
- GeneralClass 12All
In which book endangered species are listed?
Endangered species are officially listed in the Red Data Book, a comprehensive public document created and maintained by the International Union for Conservation of Nature (IUCN). This book catalogs species according to their extinction risk status, using scientifically established categories: Extinct, Extinct in the Wild, Critically Endangered, Endangered, Vulnerable, Near Threatened, Least Concern, and Data Deficient. The Red Data Book provides detailed information about each listed species
- GeneralClass 12All
(a) Why should we not let water collect anywhere in the neighborhood? (b) Name one animal disease caused: (i) by virus (ii) by bacteria (iii) by fungus
Preventing water accumulation in neighborhoods is critical because stagnant water serves as the primary breeding ground for mosquitoes, which are vectors for life-threatening diseases including malaria, dengue, chikungunya, and Zika virus. Female mosquitoes lay eggs in standing water, and larvae develop through several stages over 7-10 days before emerging as disease-carrying adults. Even small amounts of water in discarded containers, tires, flowerpots, blocked drains, or puddles can support
- GeneralClass 12All
Name the micro-organism used in bread-making which makes the bread-dough rise. How does it make the dough rise?
Baker's yeast, scientifically named Saccharomyces cerevisiae, is the microorganism used in bread-making that causes dough to rise and develop its characteristic light, fluffy texture. This single-celled fungus has been used in baking for thousands of years and is available commercially as active dry yeast, instant yeast, or fresh compressed yeast. When mixed into bread dough containing flour, water, sugar, and salt, the yeast cells begin metabolizing available sugars through the ferm
- GeneralClass 12All
(a) What is meant by food preservation? Name any five methods of preserving food. (b) How do you preserve cooked food at home?
Food preservation refers to the treatment and handling of food to prevent spoilage caused by microorganisms (bacteria, yeasts, molds), slow down enzyme activity, and maintain nutritional value, texture, flavor, and safety for extended periods beyond normal shelf life. Since ancient times, humans have developed preservation methods to ensure food availability during seasons of scarcity, reduce waste, enable long-distance transportation, and prevent foodborne illness. Five major preservation me
- GeneralClass 12All
Describe the method of pasteurization for the preservation of milk.
Pasteurization is a heat treatment process named after Louis Pasteur that preserves milk by heating it to specific temperatures for controlled time periods to kill harmful pathogenic bacteria while retaining nutritional value, flavor, and overall quality better than boiling. The most common method is High Temperature Short Time (HTST) pasteurization, where milk is rapidly heated to 72°C (161°F) and held at that temperature for 15 seconds before being quickly cooled to 4°C or below
- GeneralClass 12All
(a) What is meant by communicable disease? Name any two communicable diseases. (b) What are the various ways in which communicable diseases can occur and spread?
Communicable diseases, also called infectious or contagious diseases, are illnesses caused by pathogenic microorganisms (bacteria, viruses, fungi, parasites) that can be transmitted directly or indirectly from one person to another, or from animals to humans. These diseases spread when pathogens leave an infected host and successfully enter a susceptible individual, establishing infection in the new host. Two common examples are tuberculosis (TB), a bacterial infection primarily affecting the
- GeneralClass 12All
(a) Name any five human diseases caused by microorganisms. Also name the causative microorganisms and mode of transmission for each of these diseases. (b) State the various ways of preventing the occurrence and spreading of communicable diseases.
Five significant human diseases caused by microorganisms demonstrate the diversity of pathogens and transmission routes. Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis and spreads through airborne droplets when infected individuals cough, sneeze, or talk, primarily affecting the lungs but potentially spreading to other organs. Malaria results from parasitic protozoa (Plasmodium falciparum, P. vivax, and others) transmitted through the bite o
- GeneralClass 12All
(a) What is a vaccine? How does a vaccine work? (b) Why are children given vaccination?
A vaccine is a biological preparation containing weakened, killed, or fragmented forms of disease-causing microorganisms (or their toxins) that stimulates the body's immune system to develop protection against specific infectious diseases without causing the actual illness. Vaccines work by introducing antigens—molecular components recognized as foreign by the immune system—which trigger the production of antibodies and activate immune memory cells without the risks associated wit
- GeneralClass 12All
What is meant by "nitrogen fixation"? State two ways in which nitrogen gas of the atmosphere can be 'fixed' in nature to get nitrogen compounds in the soil.
Nitrogen fixation is the process of converting atmospheric nitrogen gas (N₂), which makes up 78% of Earth's atmosphere but cannot be directly used by most living organisms, into nitrogen compounds such as ammonia (NH₃), nitrates (NO₃⁻), or nitrites (NO₂⁻) that plants can absorb and utilize for synthesizing proteins, nucleic acids, and other essential biomolecules. Although nitrogen is abundant in the atmosphere, the strong triple bond between nitrogen atoms makes N₂ extremely unreactive and u
- GeneralClass 12All
Large scale deforestation leads to decreases in the amount of gas A in the atmosphere whereas the amount of gas B increases. The increased amount of gas B in the atmosphere causes an effect C which leads to excessive heating of the earth and its atmosphere producing an undesirable phenomenon D. What are A, B, C and D?
Gas A is oxygen, which decreases when large-scale deforestation occurs because trees are the primary producers of oxygen through photosynthesis. Gas B is carbon dioxide, which increases because trees that normally absorb CO₂ are removed, and burning or decomposition of felled trees releases stored carbon back into the atmosphere. This creates a double impact—losing carbon-absorbing capacity while simultaneously adding more carbon dioxide to the air.
- GeneralClass 12All
Draw a neat, labeled diagram of nitrogen cycle in nature. Which natural phenomenon occurring in the sky is responsible for nitrogen fixation?
The nitrogen cycle illustrates how nitrogen circulates through the atmosphere, soil, living organisms, and back to the atmosphere in a continuous biogeochemical cycle. The cycle begins with nitrogen fixation, where atmospheric nitrogen gas (N₂) is converted into ammonia by nitrogen-fixing bacteria (Rhizobium in root nodules and free-living Azotobacter) and by lightning strikes. The ammonia produced is then converted to nitrites and nitrates through nitrification by soil bact
- GeneralClass 12All
Name one Wildlife Sanctuary and one National Park of Pachmarhi Biosphere Reserve.
The Pachmarhi Biosphere Reserve in Madhya Pradesh contains the Satpura National Park and the Bori Wildlife Sanctuary. Established in 1999, this biosphere reserve was India's first designated biosphere reserve and serves as a critical conservation area protecting unique flora and fauna of the Satpura range. The reserve spans approximately 4,926 square kilometers and encompasses multiple protected zones working together to preserve biodiversity. The Sat
- GeneralClass 12All
Fill in the following blanks with suitable words: (a) Deforestation increases the level of _______ in the atmosphere. (b) Species found only in a particular area is known as ______ species. (c) A place where animals are protected in their natural habitat is called _______. (d) Satpura National Park is a part of ______ Biosphere Reserve. (e) Red Data Book contains a record of _______ species.
(a) Deforestation increases the level of carbon dioxide in the atmosphere. Trees absorb carbon dioxide during photosynthesis, acting as natural carbon sinks. When forests are cleared or burned, this stored carbon is released back into the atmosphere, and the capacity to absorb future emissions is reduced, contributing significantly to climate change and global warming. (b) Species found only in a particular area are known as e
- GeneralClass 12All
What name is given to those species: (a) that are on the verge of vanishing from earth? (b) that have died out completely.
Species on the verge of vanishing from Earth are called endangered species. These are organisms whose population numbers have declined to critically low levels, putting them at extremely high risk of extinction in the near future if protective measures are not implemented. The International Union for Conservation of Nature (IUCN) maintains detailed classifications, with "endangered" representing species facing a very high risk of extinction in the wild, while "critically enda
- GeneralClass 12All
How can infection by microorganisms be checked in poultry?
Preventing and controlling microbial infections in poultry requires comprehensive biosecurity measures starting with maintaining strict hygiene and sanitation in poultry houses, including regular cleaning, disinfection of equipment and housing areas, and proper disposal of dead birds and waste material. Limit human and animal traffic into poultry facilities, use footbaths with disinfectants at entry points, and ensure workers change clothing and footwear before entering. Provide clean, uncont
- GeneralClass 12All
Name two common carriers of disease causing microbes.
Houseflies and mosquitoes are two of the most common carriers (vectors) of disease-causing microbes, responsible for transmitting numerous serious illnesses to humans worldwide. Houseflies (Musca domestica) are mechanical vectors that physically carry pathogens on their hairy legs, bodies, and mouthparts after landing on feces, garbage, sewage, and decaying matter. When flies subsequently land on human food, utensils, or food preparation surfaces, they contaminate them with bacteria,
- GeneralClass 12All
Explain how soil gets affected by the repeated growing of crops in the same fields.
Soil gets significantly affected by repeated growing of crops in the same fields through a process called nutrient depletion and soil degradation. When the same crop is cultivated continuously, it repeatedly extracts the same set of nutrients from the soil in similar proportions, leading to deficiency of those specific nutrients that the crop demands in large quantities. For instance, cereal crops like wheat and rice are heavy feeders of nitrogen, so continuous cultivation depletes soil nitro