General Q&A for Class 12 · Page 64
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What are unwanted plants that grow alongside crop plants called?
These unwanted plants are called weeds. Weeds compete with crop plants for essential resources like nutrients, water, sunlight, and space, reducing crop yields significantly. Examples include Xanthium (cocklebur), Parthenium (carrot grass), and Cyperinus rotundus (purple nutsedge). Weeds also harbor pests and diseases, interfere with harvesting, and reduce crop quality. Effective weed management through mechanical, chemical, or biological methods is
- GeneralClass 12All
What are three factors responsible for grain loss during storage?
Three major factors causing grain loss during storage are biotic factors (insects, rodents, birds, mites, and microorganisms like bacteria and fungi), abiotic factors (moisture content, temperature, and humidity that promote pest growth and grain deterioration), and inadequate storage infrastructure (poor ventilation, improper containers, and lack of protective treatments). These factors can lead to 10-30% post-harvest losses. Proper storage
- GeneralClass 12All
How are fungi useful to us as food material?
Fungi serve as valuable food sources in multiple ways. Edible mushrooms like button mushrooms, oyster mushrooms, and shiitake are consumed directly and are rich in protein, vitamins, and minerals. Yeast, a type of fungus, is essential for baking bread, brewing beer, and producing wine through fermentation. Some fungi are also used to produce enzymes and organic acids used in food processing. Additionally, certain fungi like Penicillium are used in ch
- GeneralClass 12All
What is farming with minimal or no chemicals called?
This approach is called organic farming. Organic farming relies on natural inputs like compost, green manure, biofertilizers, and biopesticides instead of synthetic chemicals. It emphasizes crop rotation, companion planting, biological pest control, and maintaining soil health through organic matter. Organic farming produces healthier food, protects environmental quality, conserves biodiversity, and promotes sustainable agriculture. It builds long-term soil fertility and redu
- GeneralClass 12All
What are the common chemical fertilizers used?
Common chemical fertilizers include urea (providing 46% nitrogen), diammonium phosphate or DAP (containing nitrogen and phosphorus), muriate of potash (rich in potassium), ammonium sulfate (supplying nitrogen and sulfur), and superphosphate (providing phosphorus). These fertilizers are manufactured industrially and provide concentrated nutrients in readily available forms. NPK fertilizers contain all three pr
- GeneralClass 12All
Which contains humus - manure or fertilizers?
Manure contains humus, while chemical fertilizers do not. Humus is the dark, organic component of soil formed from decomposed plant and animal matter. Organic manures like farmyard manure, compost, and green manure are rich in humus, which improves soil structure, water retention, aeration, and microbial activity. Chemical fertilizers provide only specific nutrients without adding organic matter, making manure superior for long-term soil health despite its lower nutrient conc
- GeneralClass 12All
What are the three primary necessities of human beings fulfilled by plants?
Plants fulfill three fundamental human needs: food, clothing, and shelter. Plants provide food through cereals, pulses, fruits, and vegetables that supply energy and essential nutrients. Cotton, jute, and flax plants provide fibers for clothing and textiles. Wood from trees is used for constructing homes, furniture, and various building materials. Additionally, plants supply oxygen, medicines, and fuel, making them indispensable to human survival and well-being.
- GeneralClass 12All
Which three nutrients do plants take up directly from the atmosphere?
Plants absorb three essential nutrients directly from the atmosphere: carbon (C), hydrogen (H), and oxygen (O). Carbon dioxide is absorbed through leaf stomata during photosynthesis, where it combines with water to produce glucose and oxygen. Oxygen is absorbed for respiration, and hydrogen comes from water vapor and water absorbed by roots. These three elements constitute the majority of plant dry matter and are fundamental
- GeneralClass 12All
What is silviculture?
Silviculture is the science and practice of cultivating and managing forests and forest trees. It involves the establishment, growth, composition, health, and quality of forests to meet diverse needs and values. Silviculture practices include tree planting, thinning, pruning, and harvesting timber in sustainable ways. This field is crucial for maintaining ecological balance, providing timber and non-timber forest products, conserving biodiversity, and mitigating climate chang
- GeneralClass 12All
. How do plants take up nutrients from the soil?
Plants absorb nutrients from soil primarily through their root system via two mechanisms. Active absorption uses energy to take up nutrients against concentration gradients through specialized root hair cells. Passive absorption occurs when nutrients move from higher to lower concentration areas without energy expenditure. Nutrients must be dissolved in soil water to be absorbed. The root hairs greatly increase the surface area for absorption
- GeneralClass 12All
What branch of science deals with the study of bones?
Osteology is the branch of science dedicated to studying bones. This specialized field of anatomy examines bone structure, function, development, and the skeletal system's role in supporting the body, protecting organs, facilitating movement, and producing blood cells. Osteologists study bone composition, growth patterns, diseases, fractures, and evolutionary adaptations. This knowledge is crucial in medicine, forensics, anthropology, and paleontology, helping diagnose bone d
- GeneralClass 12All
What tissues make up the brain and spinal cord?
The brain and spinal cord are primarily composed of nervous tissue (also called neural tissue). This specialized tissue consists of two main cell types: neurons (nerve cells) that transmit electrical signals, and neuroglia (supporting cells) that provide structural support, insulation, and nutrition. Nervous tissue in the central nervous system is organized into gray matter (cell bodies) and white matter (myelinated nerve fibers). This complex tissue enables processing, integ
- GeneralClass 12All
What are the small, branched processes of nerve cells called?
The small, branched processes extending from nerve cells are called dendrites. These tree-like projections receive electrical and chemical signals from other neurons and transmit them toward the cell body. Dendrites significantly increase the surface area of neurons, allowing a single nerve cell to receive input from thousands of other neurons simultaneously. This branching architecture is essential for complex information processing in the nervous system, enabling the integr
- GeneralClass 12All
What nutrients do we obtain from cereals, fruits, and vegetables?
Cereals provide carbohydrates for energy, fruits supply vitamins and minerals (especially vitamin C), and vegetables offer dietary fiber, vitamins, and minerals. Together, these food groups form the foundation of a balanced diet, providing essential nutrients for growth, development, and disease prevention.
- GeneralClass 12All
Which three micronutrients are required by plants?
The three essential micronutrients required by plants are iron (Fe), zinc (Zn), and manganese (Mn). While plants need these nutrients in small quantities, they are crucial for various physiological processes including chlorophyll formation, enzyme activation, and protein synthesis. Deficiency of these micronutrients can significantly reduce crop yield and quality.
- GeneralClass 12All
What is an example of an organic compound used as fertilizer?
Compost is a widely used organic fertilizer made from decomposed plant and animal matter. It improves soil structure, enhances water retention, and provides a slow, steady release of nutrients. Other examples include farmyard manure, vermicompost, and green manure, all of which enrich soil fertility naturally.
- GeneralClass 12All
What are nutrients and how many are essential for plant growth?
Nutrients are chemical elements that plants absorb from soil and atmosphere to grow and develop properly. Plants require 16 essential nutrients: three from air and water (carbon, hydrogen, oxygen), three primary macronutrients (nitrogen, phosphorus, potassium), three secondary macronutrients (calcium, magnesium, sulfur), and seven micronutrients (iron, manganese, zinc, copper, boron, molybdenum, chlorine).
- GeneralClass 12All
What does NPK stand for in fertilizers?
NPK stands for Nitrogen (N), Phosphorus (P), and Potassium (K) - the three primary macronutrients essential for plant growth. Nitrogen promotes leaf growth and gives plants their green color, phosphorus supports root development and flowering, while potassium enhances overall plant health and disease resistance. The NPK ratio on fertilizer packages indicates the percentage of each nutrient.
- GeneralClass 12All
Can you name a biofertilizer?
Rhizobium is a common biofertilizer that consists of beneficial bacteria living in the root nodules of leguminous plants. These bacteria convert atmospheric nitrogen into forms that plants can absorb, reducing the need for chemical nitrogen fertilizers. Another example is Azotobacter, which also fixes nitrogen in the soil.
- GeneralClass 12All
What are three common examples of pulses?
Three common pulses are lentils (masoor), chickpeas (chana), and green gram (moong). Pulses are edible seeds from legume plants that are rich in protein and essential nutrients. They play a vital role in crop rotation and soil fertility by fixing atmospheric nitrogen through their root nodules.