General Q&A for Class 12 · Page 258
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Define sustainable agriculture
Sustainable agriculture is a farming approach that focuses on producing food, fiber, and other plant or animal products in ways that protect the environment, support economic viability, and promote social equity for present and future generations. It emphasizes practices that maintain soil health, conserve water, minimize chemical inputs, preserve biodiversity, and reduce environmental degradation while ensuring farmers can maintain productive and profitable operations. The core principle is
- GeneralClass 12All
Why are manures and fertilizer used in fields
Manures and fertilizers are added to field mainly to replenish minerals which get depleted due to withdrawal by crop plants and leaching down to lower strata of soil. (i) Manures add small quantity of all minerals to the soil. They improve soil hydration, soil aeration and activity of soil micro- organism, some of which are required for solubilisation of heavy minerals.
- GeneralClass 12All
Explain any one method of crop production which ensures high yield.
Rotation of crops is a method of crop production which ensures high yield. Crop rotation is growing of different crop on the same piece of land in a preplanned succession. Crop rotation is done for one year, two year and three year cycle. Crops chosen are such that they withdraw nutrients from different layers of the soil. Crop rotation involving a leguminous crop ensures that the soil gets naturally enriched with nitroge
- GeneralClass 12All
What factors may be responsible for huge losses during strorage ?
Abiotic Factors. Excess moisture in grains, dampness and high temperature in storage place. Biotic Factors. Insects, mites, rodents, birds, fungi and bacteria.
- GeneralClass 12All
What are the different types of parenchyma? Write their special features.
Parenchyma is a simple permanent plant tissue with thin-walled, living cells that serves various functions, and it differentiates into specialized types based on specific roles. The main types include chlorenchyma (parenchyma with chloroplasts for photosynthesis), aerenchyma (parenchyma with large air cavities for buoyancy and gas exchange), and storage parenchyma (for storing food, water, or waste products). Each type has structural modifications that make it exceptionally suited to its part
- GeneralClass 12All
Give the examples of some involuntary movements.
Involuntary movements are actions controlled by the autonomic nervous system that occur without conscious thought or deliberate control. Common examples include the beating of your heart (cardiac muscle contractions), the rhythmic contractions of the digestive tract that move food along (peristalsis), breathing during sleep, blinking to keep eyes moist, blood vessel constriction or dilation to regulate blood pressure and body temperature, and the constant adjustments your pupils make to contr
- GeneralClass 12All
Based on the cell layers and shape of cells, state the different types of epithelial tissues.
Epithelial tissues are systematically classified using a two-part naming system that combines the number of cell layers with the predominant cell shape. Based on cell layers, epithelia are either simple (single layer of cells), stratified (multiple layers), or pseudostratified (appears multi-layered but all cells touch the basement membrane, though not all reach the surface). The three basic cell shapes are squamous (flat and scale-like), cuboidal (roughly equal in height and width, cube-shap
- GeneralClass 12All
Which tissue is called loose connective tissue?
Areolar tissue is commonly referred to as loose connective tissue because of its loosely arranged fibers and abundant ground substance. This tissue has a gel-like matrix containing irregularly distributed collagen and elastic fibers, with plenty of space between them filled with tissue fluid. You'll find areolar tissue beneath the skin (connecting it to underlying muscles), surrounding blood vessels and nerves, and filling spaces between organs throughout the body. The "loose" structu
- GeneralClass 12All
Write the name of most abundant muscular tissue found in our body.
Skeletal muscle tissue is the most abundant muscular tissue in the human body, comprising approximately 40-45% of total body weight in adults. This voluntary muscle tissue is attached to bones via tendons and is responsible for all conscious movements we make, from walking and lifting objects to facial expressions and maintaining posture. The term "skeletal" reflects its primary function of moving the skeletal system. What makes skeletal muscle distinctive is its striated appearance u
- GeneralClass 12All
Name the different types of epithelial tissues.
Epithelial tissues are classified based on two key features: the number of cell layers and the shape of the cells. The main types include simple epithelium (single layer), stratified epithelium (multiple layers), and pseudostratified epithelium (appears layered but isn't). Based on cell shape, we have squamous (flat, scale-like cells), cuboidal (cube-shaped cells), and columnar (tall, column-like cells) epithelial tissues. When we combine these characteristics, we get specific tissue
- GeneralClass 12All
Why should preventive measures and biological cantrol methods are preferred for protection crops ?
Preventive measures and biological control methods do not allow any measurable loss in quality and quantity of crops. They also do not cause any degradation of the environment. Cost is also very small. Preventive measures protect the crops from pests. Biological control methods eliminate the pests without harming crops and other human interests.
- GeneralClass 12All
Which of the following conditions will give the most benefits ? Why ? (a) Farmers use high quality seed but do not adopt irrigation or use fertilizers. (b) Farmers use ordinary seeds, adopt irrigation and use fertilizers. (c) Farmers use quality seeds, adopt irrigation, use fertilizers and crop protection measures
Farmers are benefitted when they use quality seeds. irrigarion fertilizers and crop protection measures (choice c). Ordinary seeds cannot yield very high due to poor quality while quality seeds without necessary inputs yield low.
- GeneralClass 12All
How do plants get nutrients ?
Plant obtain nutrients from air, water and soil. Air is the source of carbon and oxygen. Hydrogen is obtained from water. The remaining thirteen elements are taken directly from soil through root absorption.
- GeneralClass 12All
Name the types of vacuoles. Which one takes part in osmoregulation?
Vacuoles are classified into several types based on their function and contents. Plant cells typically have a large central vacuole (also called sap vacuole) that occupies 50-90% of the cell volume, storing water, nutrients, pigments, waste products, and maintaining turgor pressure. Food vacuoles (phagosomes) form when cells engulf food particles through phagocytosis, containing the ingested material until it fuses with lysosomes for digestion—common in protozoans like Amoeba. Contracti
- GeneralClass 12All
What are the desirable agronomic characteristics for crop improvement ?
They are different for different crops. Cereals should be dwarf but with large ears. Dwarfness makes their stem stronger. They can withstand lodging affect of strong winds. Nutrient requirement is also less. Large ears produce more grains. Legumes should have more pods which generally develop in relation to stem IMPROVEMENT IN FOOD RESOURCES 101 branching. Therefore, more branching and good foliage increas
- GeneralClass 12All
How do biotic and abiotic factors adversely effect crop production ?
. Biotic factors are living organisms that reduce crop productivity due to either directly feeding on them (e.g., insects, rodents) or causing diseases (e.g., nematodes, mycoplasmas, bacteria, viruses, fungi). Abiotic factors are non-living components of environment that effect growth of crop plants like excess of water (water-logging), scarcity of water drought, salinity, heat, cold or frost. Water logging reduces aerati
- GeneralClass 12All
What do we get from cereals, pulses, fruits and vegetables ?
Cereals. Mostly carbohydrates Pulses. Mostly proteins Fruits. Vitamins, minerals, organic acids. Vegetables. Vitamins, minerals, small quantities of proteins, carbohydrates and oil.
- GeneralClass 12All
What are the functions of stomata?
Stomata are microscopic pores on plant surfaces, primarily leaf epidermis, that serve as the critical gateway for gas exchange between the plant's internal tissues and the external atmosphere. The primary function of these adjustable openings is to facilitate carbon dioxide uptake for photosynthesis while simultaneously allowing oxygen—produced as a photosynthetic byproduct—to diffuse out. Each stoma is bordered by two specialized guard cells that can swell or shrink in response t
- GeneralClass 12All
What is the function of phloem?
Phloem serves as the plant's food distribution system, transporting photosynthetically produced sugars and other organic nutrients from source organs (primarily leaves) to sink organs (roots, fruits, developing shoots, and storage tissues) throughout the plant body. This bi-directional transport system moves nutrient-rich sap through specialized living cells called sieve tube elements, which form continuous channels stacked end-to-end with perforated sieve plates facilitating flow. Unlike xyl
- GeneralClass 12All
Name the two types of cells found in sclerenchymatous tissue
Sclerenchymatous tissue comprises two distinct cell types: fibers and sclereids, each with unique structural characteristics and functional roles in plant support. Fibers are elongated, slender cells with tapering ends that can measure several millimeters in length, arranged in bundles that run parallel to the long axis of plant organs. These cells have thick, heavily lignified walls with a very narrow or obliterated lumen (central cavity), providing tensile strength that prevents breakage wh