General Q&A for Class 12 · Page 60
5,215 free answers in General for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Which acid is secreted by the gastric glands in the stomach?
The gastric glands in the stomach secrete Hydrochloric acid (HCl), a strong mineral acid that plays multiple critical roles in digestion: Functions of Gastric HCl: pH Regulation: Creates an acidic environment (pH 1.5-3.5) optimal for enzyme activity Enzyme Activation: Converts inactive pepsinogen into active pepsin, the primary protein-digesting enzyme Protein Denaturation</s
- GeneralClass 12All
What glands are associated with the human digestive system?
The human digestive system includes several important glands that secrete enzymes, acids, and other substances essential for digestion: Major Digestive Glands: Salivary Glands (3 pairs) Location: Mouth region Types: Parotid, submandibular, and sublingual glands Secretion: Saliva containing salivary amylase (ptyalin) for starch digestion
- GeneralClass 12All
What is photolysis of water?
Photolysis of water is the light-dependent splitting of water molecules that occurs during photosynthesis. This critical process takes place in the thylakoid membranes of chloroplasts during the light reactions. When light energy is absorbed by chlorophyll and other photosynthetic pigments, it triggers the breakdown of water molecules (H₂O) into hydrogen ions (H⁺), electrons (e⁻), and oxygen gas (O₂). The chemical equation for this process is: 2H₂O &ra
- GeneralClass 12All
What is the source of oxygen in photosynthesis?
The source of oxygen released during photosynthesis is water (H₂O), not carbon dioxide as commonly misunderstood. This was scientifically proven through experiments using isotope labeling techniques. During the light-dependent reactions of photosynthesis, water molecules undergo photolysis (light-driven splitting) in the thylakoid membranes of chloroplasts. When water splits, it produces: Oxygen gas (O₂) – released into the atmosp
- GeneralClass 12All
What are the end products of dark reactions of photosynthesis?
The dark reactions of photosynthesis, also called the Calvin cycle or light-independent reactions, produce glucose (a simple sugar) as the primary end product, along with other important byproducts. Main end products: Glucose (C₆H₁₂O₆): The principal carbohydrate product that serves as an energy source and building block for more complex carbohydrates like starch and cellulose. <l
- GeneralClass 12All
Which type of nutrition takes place in fungi?
Fungi exhibit saprophytic (or saprotrophic) nutrition, which is a heterotrophic mode of nutrition. Unlike plants, fungi cannot produce their own food through photosynthesis because they lack chlorophyll. How saprophytic nutrition works in fungi: Secretion of enzymes: Fungi secrete powerful digestive enzymes onto dead and decaying organic matter, such as fallen leaves, dead wood, animal remains, and other organic waste.<
- GeneralClass 12All
How do autotrophs obtain CO₂ and nitrogen (H₂O) to make their food?
Autotrophs, particularly green plants, have evolved efficient mechanisms to obtain raw materials for photosynthesis: Carbon Dioxide (CO₂) Acquisition: Terrestrial Plants: Absorb CO₂ from the atmosphere through tiny pores called stomata located primarily on leaf surfaces (usually on the underside) Aquatic Plants: Dissolve CO₂ directly from water where it exists as dissolved gas or carbonic acid
- GeneralClass 12All
What do you mean by biodiversity?
Biodiversity (biological diversity) refers to the variety and variability of life on Earth at all levels of biological organization. It encompasses three main dimensions: Species diversity: The variety of different species in a particular region or ecosystem (e.g., tropical rainforests have extremely high species diversity) Genetic diversity: Variation in genetic makeup within species populations, enabling ada
- GeneralClass 12All
Define classification.
Classification is the systematic organization of living organisms into hierarchical groups based on shared characteristics, evolutionary relationships, and structural similarities. This scientific process involves: Identifying organisms based on observable and molecular traits Grouping them into categories (taxa) from broad to specific Naming according to standardized nomenc
- GeneralClass 12All
Name the scientists who gave 2-kingdom and 5-kingdom classification, respectively.
Two-Kingdom Classification: Proposed by Carolus Linnaeus in the 18th century, dividing all life into: Kingdom Plantae (plants) Kingdom Animalia (animals) This simple system became inadequate as microscopy revealed organisms that didn't fit neatly into either category. Five-Kingdom Classification: Proposed by Robert H. Whittaker in 1969<
- GeneralClass 12All
Define sub-kingdom Phanerogamae.
Sub-kingdom Phanerogamae (meaning "visible reproduction") comprises seed-bearing plants with well-developed, conspicuous reproductive structures. The term derives from Greek "phaneros" (visible) and "gamos" (marriage/reproduction). Defining characteristics: Seed production: Reproduce through seeds rather than spores Well-developed reproductive organs: Flowers
- GeneralClass 12All
Give any two distinctive characteristics of chordates.
Two defining characteristics of phylum Chordata (present at least during embryonic development): Notochord: A flexible, rod-like supporting structure running along the back (dorsal side) of the organism. In primitive chordates and embryos, it provides skeletal support. In vertebrates, it's largely replaced by the vertebral column (backbone) during development, though remnants persist as intervertebral discs.
- GeneralClass 12All
What is the importance of electron emission from chlorophyll during photosynthesis?
Electron Emission from Chlorophyll: When chlorophyll molecules absorb light energy, electrons in the chlorophyll are excited to higher energy levels and are eventually ejected. This process is crucial for several reasons: Energy Conversion: Converts light energy into chemical energy by initiating the electron transport chain ATP Synthesis: The flow of electrons through the electron transport chain creates a pr
- GeneralClass 12All
What is the CO₂ acceptor during the dark reaction of C3 photosynthesis?
The CO₂ acceptor in the dark reaction (Calvin cycle) of C3 photosynthesis is Ribulose-1,5-bisphosphate (RuBP), a five-carbon sugar molecule. During carbon fixation, the enzyme RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) catalyzes the attachment of CO₂ to RuBP, forming an unstable six-carbon intermediate that immediately splits into two molecules of 3-phosphoglycerate (3-PGA), a three-carbon compound. This is the first stable product of C3 photosynthesis, which i
- GeneralClass 12All
What is the product formed during the C3 cycle of the dark reaction?
The primary product formed during the C3 cycle (Calvin cycle) is glucose (C₆H₁₂O₆), a six-carbon sugar molecule. However, the immediate products and intermediates include: Immediate Products: 3-Phosphoglycerate (3-PGA): First stable three-carbon compound formed when CO₂ combines with RuBP Glyceraldehyde-3-phosphate (G3P or PGAL): A three-carbon sugar that is the actual product of the Calvin cy
- GeneralClass 12All
What are the different modes of nutrition and how are they classified?
Nutrition modes are classified into two main categories based on how organisms obtain food: Autotrophic Nutrition (Self-feeding) Organisms synthesize their own food from inorganic substances using external energy sources. Photoautotrophs: Use light energy for food synthesis Example: Green plants, algae, and cyanobacteria perform photosynthesis Chemoautotrophs:
- GeneralClass 12All
What is the symbiotic association between fungi and algae called?
The symbiotic association between fungi and algae is called lichen. In this unique partnership, the fungus provides protection, moisture retention, and structural support, while the algae or cyanobacteria (photobiont) perform photosynthesis to produce food for both organisms. This mutualistic relationship allows lichens to thrive in extreme environments where neither organism could survive independently, such as bare rocks, tree bark, and arctic tundra. Lichens serve as impor
- GeneralClass 12All
Define birds. Give two examples of flightless birds.
Birds (Class Aves) are warm-blooded, egg-laying vertebrates characterized by: Defining features: Feathers - Unique to birds, providing insulation and enabling flight Wings - Modified forelimbs (though not all birds fly) Beaks/Bills - Without teeth Four-chambered heart - Efficient circulatory system Hollow
- GeneralClass 12All
Where do light and dark reactions of photosynthesis occur?
Light Reaction (Light-dependent reaction) Location: Thylakoid membranes of chloroplasts (grana) Function: Converts light energy into chemical energy (ATP and NADPH) Requirements: Requires sunlight, chlorophyll, and water Products: ATP, NADPH, and oxygen (released as byproduct) Dark Reaction (Calvin Cycle/Light-independent reaction)<
- GeneralClass 12All
Name all phyla which are included in Kingdom Animalia.
The major phyla of Kingdom Animalia include: Non-chordates (Invertebrates): Porifera - Sponges Coelenterata/Cnidaria - Jellyfish, corals, hydra Platyhelminthes - Flatworms Nematoda/Aschelminthes - Roundworms Annelida - Segmented worms (earthworms, leeches) Arthropoda - Insects, spiders,