CBSE Class 11 Biology Flashcards

24 sample cards from the Biology deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Define tidal volume, vital capacity, and residual volume.

   Tidal volume (TV): volume of air inspired or expired in a normal breath (~500 mL). Vital capacity (VC): maximum air a person can breathe out after a maximum inspiration (ERV + TV + IRV). Residual volume (RV): volume of air remaining in the lungs after a maximal expiration (~1100–1200 mL).

2. How is oxygen and carbon dioxide transported in human blood?

   Oxygen is transported mainly (~97%) as oxyhaemoglobin (bound to haemoglobin) and ~3% dissolved in plasma. CO2 is transported ~70% as bicarbonate ions (HCO3-) in plasma, ~20–25% as carbamino-haemoglobin (bound to Hb), and ~7% dissolved in plasma.

3. Name the components and functions of human blood.

   Blood is a fluid connective tissue with plasma (~55%, mostly water with proteins like albumin, globulin, fibrinogen) and formed elements (~45%): RBCs/erythrocytes (carry O2 via haemoglobin), WBCs/leukocytes (immunity/defence), and platelets/thrombocytes (blood clotting).

4. Describe the double circulation of blood in humans.

   Double circulation means blood passes through the heart twice per complete cycle. Pulmonary circulation: deoxygenated blood goes from the right ventricle to the lungs and oxygenated blood returns to the left atrium. Systemic circulation: oxygenated blood goes from the left ventricle to body tissues and deoxygenated blood returns to the right atrium.

5. What are nitrogenous excretory products, and classify animals as ammonotelic, ureotelic, and uricotelic.

   Ammonotelic animals excrete ammonia (most toxic, needs much water; e.g. bony fishes, aquatic amphibians). Ureotelic animals excrete urea (less toxic; e.g. mammals, many adult amphibians, marine fishes). Uricotelic animals excrete uric acid (least toxic, least water; e.g. reptiles, birds, insects, land snails).

6. Name the structural and functional unit of the kidney and its main parts.

   The nephron is the structural and functional unit of the kidney (~1 million per kidney). Its parts are the Malpighian/renal corpuscle (glomerulus enclosed by Bowman's capsule) and the renal tubule (proximal convoluted tubule, loop of Henle, distal convoluted tubule, leading to the collecting duct).

7. List the three main steps of urine formation in the nephron.

   (1) Glomerular filtration (ultrafiltration of blood in the glomerulus/Bowman's capsule forming filtrate), (2) Reabsorption (selective reabsorption of useful substances like glucose, amino acids, water, ions in the tubules), and (3) Secretion (tubular secretion of H+, K+, NH3 into the filtrate to maintain ionic and acid-base balance).

8. Differentiate the three types of muscle tissue (skeletal, smooth, cardiac).

   Skeletal (striated) muscle: striated, multinucleate, voluntary, attached to bones. Smooth (visceral) muscle: non-striated, spindle-shaped, uninucleate, involuntary, in walls of internal organs. Cardiac muscle: striated, branched, uninucleate, involuntary, found only in the heart, with intercalated discs.

9. Name the proteins involved in muscle contraction and outline the sliding filament theory.

   The main proteins are actin (thin filament), myosin (thick filament), and the regulatory proteins troponin and tropomyosin. By the sliding filament theory, muscle contraction occurs when actin (thin) filaments slide over myosin (thick) filaments; cross-bridges form, the sarcomere shortens, the H-zone and I-band shrink, but the A-band length stays constant. It requires Ca2+ and ATP.

10. Name the three types of skeletal joints (functional) with examples.

    Fibrous (immovable) joints, e.g. the sutures of the skull; Cartilaginous (slightly movable) joints, e.g. between adjacent vertebrae; and Synovial (freely movable) joints, e.g. ball-and-socket (shoulder, hip) and hinge (knee, elbow) joints.

11. Describe the structure of a neuron and name its three parts.

    A neuron is the structural and functional unit of the nervous system. Its three parts are: the cell body/cyton (contains nucleus and cytoplasm with Nissl's granules), dendrites (short branched processes that receive impulses), and the axon (a single long process that transmits impulses away from the cell body, often myelinated).

12. What is a resting membrane potential and an action potential in a neuron?

    The resting potential is the polarised state of a non-conducting axon membrane (~ -70 mV, with more Na+/positive outside and K+/negative inside, maintained by the Na+/K+ pump). An action potential (nerve impulse) is a transient reversal (depolarisation) of this potential when Na+ rushes in, followed by repolarisation as K+ moves out.

13. How is a nerve impulse transmitted across a chemical synapse?

    At a chemical synapse, the arriving impulse triggers Ca2+ influx into the pre-synaptic axon terminal, causing synaptic vesicles to release neurotransmitters (e.g. acetylcholine) into the synaptic cleft. These bind to receptors on the post-synaptic membrane, opening ion channels and generating a new impulse in the post-synaptic neuron.

14. Differentiate the central nervous system (CNS) and the peripheral nervous system (PNS).

    The CNS consists of the brain and spinal cord and is the site of information processing and control. The PNS consists of all the nerves (cranial and spinal) connecting the CNS to body parts; it has an afferent (sensory) division carrying impulses to the CNS and an efferent (motor) division carrying impulses from the CNS to effectors.

15. Differentiate the sympathetic and parasympathetic nervous systems.

    Both are divisions of the autonomic nervous system. The sympathetic system prepares the body for emergency 'fight or flight' responses (increases heart rate, dilates pupils, inhibits digestion). The parasympathetic system promotes 'rest and digest' activities (slows heart rate, constricts pupils, stimulates digestion) — they are antagonistic.

16. Name the major endocrine glands and one key hormone secreted by each.

    Hypothalamus (releasing hormones), Pituitary (GH, TSH, ACTH, etc.), Thyroid (thyroxine/T4, T3), Parathyroid (PTH), Adrenal (adrenaline, cortisol), Pancreas (insulin, glucagon), Pineal (melatonin), Thymus (thymosin), and Gonads — testes (testosterone) and ovaries (estrogen, progesterone).

17. What is the difference between endocrine and exocrine glands?

    Endocrine (ductless) glands secrete hormones directly into the blood, which act on distant target organs (e.g. thyroid, pituitary). Exocrine glands have ducts that carry their secretions (enzymes, sweat, saliva) to a specific site or surface (e.g. salivary glands, sweat glands). The pancreas is a mixed (heterocrine) gland.

18. Compare the actions of insulin and glucagon in blood glucose regulation.

    Both are secreted by the islets of Langerhans of the pancreas. Insulin (from beta cells) lowers blood glucose by promoting cellular glucose uptake and glycogenesis (glucose → glycogen). Glucagon (from alpha cells) raises blood glucose by stimulating glycogenolysis (glycogen → glucose) and gluconeogenesis in the liver. They are antagonistic.

19. Which hormones regulate calcium balance in the body and how?

    Parathyroid hormone (PTH) from the parathyroid glands raises blood calcium by stimulating bone resorption, increasing intestinal absorption (via vitamin D activation) and renal reabsorption. Calcitonin (from the thyroid) lowers blood calcium by suppressing bone resorption. They act antagonistically to maintain calcium homeostasis.

20. What hormones does the thyroid gland produce and what is their main function?

    The thyroid gland produces thyroxine (T4) and triiodothyronine (T3), which contain iodine and regulate the basal metabolic rate (BMR), growth, and development. It also secretes thyrocalcitonin (TCT/calcitonin) which lowers blood calcium. Iodine deficiency causes goitre and hypothyroidism.

21. What is a reflex action and a reflex arc?

    A reflex action is a rapid, automatic, involuntary response to a stimulus, not requiring conscious thought (e.g. knee-jerk). The reflex arc is the neural pathway involved: receptor → afferent (sensory) neuron → CNS (spinal cord, with an interneuron) → efferent (motor) neuron → effector (muscle/gland).

22. Name the three main parts of the human brain and a key function of each.

    Forebrain (cerebrum — thinking, memory, intelligence, voluntary actions; plus thalamus and hypothalamus for homeostasis), Midbrain (controls visual and auditory reflexes), and Hindbrain (cerebellum — balance and coordination; pons; medulla oblongata — controls heartbeat, breathing, blood pressure).

23. What are the five kingdoms in Whittaker's system of classification?

    R.H. Whittaker (1969) proposed five kingdoms: Monera (prokaryotes — bacteria), Protista (single-celled eukaryotes), Fungi (heterotrophic, cell wall of chitin), Plantae (multicellular autotrophs — plants), and Animalia (multicellular heterotrophs — animals). The criteria included cell structure, body organisation, mode of nutrition, and phylogeny.

24. What are guttation and transpiration, and how do they differ?

    Transpiration is the loss of water as vapour from the aerial parts (mainly stomata) of a plant. Guttation is the loss of water in liquid (droplet) form from the margins/tips of leaves through special pores called hydathodes, occurring due to root pressure when transpiration is low (e.g. early morning).

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