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Q1. The hormone released in fear is:
AdrenalineAdrenaline (also called epinephrine) is released by the adrenal glands in response to fear or stress. It prepares the body for a “fight‑or‑flight” response by increasing heart rate, blood pressure, and energy availability. Insulin regulates blood sugar, thyroxine controls metabolism, and growth hormone regulates body growth.
Q2. Geotropism is a response to:
GravityGeotropism (or gravitropism) is the growth response of a plant to gravity. Roots show positive geotropism (grow toward gravity), while shoots show negative geotropism (grow away from gravity). Light (phototropism), chemicals (chemotropism), and water (hydrotropism) are different stimuli.
Q3. Auxin helps plant cells to:
Grow longerAuxin is a plant hormone that promotes cell elongation (growing longer) in shoots and young stems. It does not cause cell death, shrinking, or rapid division (that is more associated with cytokinins). Auxin also influences phototropism and gravitropism.
Q4. Cytokinins are found in high concentration in:
Fruits and seedsCytokinins are plant hormones that promote cell division. They are synthesized in root tips but are found in high concentrations in developing fruits and seeds, as well as in young leaves and embryos. Old leaves and bark have lower levels.
Q5. Chemical communication is useful for:
Long-lasting coordinationChemical communication (via hormones) is slower than electrical impulses but provides prolonged, sustained effects (e.g., growth, development, reproduction). It is not for instant reactions (those use nerves), nor for growth stoppage or random movements. Long-lasting coordination is its key advantage.
Q6. ‘Hydro’ in hydrotropism refers to:
Water“Hydro” is Greek for water. Hydrotropism is the growth response of plants toward or away from water (e.g., roots growing toward moisture). Air (aerotropism), light (phototropism), and soil are different.
Q7. Auxin is synthesised at the:
Shoot tipAuxin (IAA) is primarily synthesised in the shoot apical meristem (shoot tip) and young leaves. From there it moves downward. Root tips also produce some auxin, but the main source for shoot growth is the shoot tip.
Q8. Blood supply to digestive system during fear:
Is reducedDuring fear or stress, adrenaline causes vasoconstriction (reduced blood flow) to the digestive system and skin, while increasing blood flow to skeletal muscles, heart, and brain. This prioritizes emergency action over digestion. It does not stop completely but is significantly reduced.
Q9. Endocrine glands are:
Ductless glandsEndocrine glands secrete hormones directly into the bloodstream without ducts – hence “ductless glands.” Exocrine glands (e.g., sweat, salivary) have ducts. Digestive glands are mostly exocrine. The term “duct glands” refers to exocrine glands.
Q10. Adrenaline prepares the body to:
Deal with emergencyAdrenaline triggers the “fight‑or‑flight” response, enabling the body to handle stressful or dangerous situations. It does not promote sleep, digestion (it inhibits it), or growth. Emergency response is its primary role.
Q11. Hormones in animals are part of the:
Endocrine systemHormones are chemical messengers produced by endocrine glands (e.g., pituitary, thyroid, adrenal). The endocrine system works alongside the nervous system for control and coordination. The other systems are not primarily involved in hormone production.
Q12. Chemical communication is generally:
Slower than electricalChemical communication (hormones) travels via the bloodstream and takes seconds to minutes to act, whereas electrical impulses (nerves) travel in milliseconds. Thus, it is slower. It is not absent, nor instant, nor faster than electrical.
Q13. Another means of communication in multicellular organisms is:
ChemicalBesides electrical (nervous) communication, multicellular organisms use chemical communication (hormones). Muscular and mechanical are not means of communication. “Electrical only” is incorrect because chemical means also exist.
Q14. When light comes from one side, auxin moves towards the:
Shady sideIn phototropism, light causes auxin to redistribute to the shaded side of the shoot. The higher auxin concentration on the shady side causes cells there to elongate more, bending the shoot toward light. Auxin does not move toward the bright side, soil, or root in this context.
Q15. Adrenaline is released directly into the:
BloodAs a hormone, adrenaline is secreted by the adrenal glands directly into the bloodstream (endocrine function). It then travels to target organs. It is not released into nerves, muscles directly, or lymph primarily.
Q16. Faster heartbeat increases supply of:
OxygenA faster heartbeat increases cardiac output, delivering more oxygen to tissues (especially muscles and brain) to meet increased demand during stress or exercise. Carbon dioxide removal also increases, but the key supply increase is oxygen. Hormones and water are not primarily increased by heart rate alone.
Q17. Electrical impulses can reach only cells that are:
Connected by nervous tissueElectrical impulses travel along neurons, which form synapses with specific target cells (muscles, glands, or other neurons). They cannot reach cells that are not connected by nervous tissue. Dividing, growing, or near blood vessels are not relevant.
Q18. Fast responses require information transfer to be:
Very quickFast responses (e.g., pulling hand from fire) rely on rapid information transfer. Nervous impulses are very quick (milliseconds). Slow or interrupted transfer would delay response; random transfer is not useful.
Q19. Plant hormones are used to coordinate:
Growth and responsesPlant hormones (auxins, gibberellins, cytokinins, abscisic acid, ethylene) regulate growth, development, tropic responses, flowering, fruit ripening, etc. They do not control digestion, circulation (plants lack circulatory system in animal sense), or only respiration.
Q20. Growth‑related movements in plants are:
SlowerGrowth‑related movements (tropisms) depend on differential cell elongation, which takes minutes to hours – they are slower than turgor‑based movements (e.g., Mimosa). They are not instant, fast, or absent.
Q21. Adrenaline is secreted by:
Adrenal glandThe adrenal glands (specifically the adrenal medulla) secrete adrenaline. The pituitary secretes many hormones (e.g., growth hormone), pancreas secretes insulin and glucagon, and thyroid secretes thyroxine.
Q22. A scary situation prepares animals for:
Fighting or runningThe “fight‑or‑flight” response to fear prepares an animal to either confront the threat or flee. Digestion, eating, and sleeping are suppressed during this state. Fighting or running are the adaptive responses.
Q23. Abscisic acid is a hormone that:
Inhibits growthAbscisic acid (ABA) is a plant stress hormone that inhibits growth, promotes seed dormancy, and causes stomatal closure during drought. It opposes growth‑promoting hormones like auxin and gibberellin. It does not increase height or promote flowering (that’s gibberellin/florigen).
Q24. Chemical compounds used for coordination are called:
HormonesHormones are chemical messengers that coordinate activities in multicellular organisms. Vitamins are nutrients, enzymes catalyze reactions, and minerals are inorganic nutrients. Hormones are the correct term for chemical coordination.
Q25. Blood is diverted mainly to:
Skeletal musclesDuring fear or stress, adrenaline diverts blood flow to skeletal muscles (for fighting or running) and to the heart and brain. Digestion and kidneys receive reduced flow. While brain also receives more, the primary massive diversion is to skeletal muscles.
Q26. Wilting of leaves is caused by:
Abscisic acidAbscisic acid (ABA) induces stomatal closure and reduces water loss, but prolonged water deficit combined with ABA can lead to wilting. Gibberellin promotes growth, auxin promotes elongation, cytokinin delays senescence – none cause wilting directly. ABA is associated with drought responses and wilting prevention, but severe water stress with ABA presence leads to wilting; the question likely refers to the hormone that when overexpressed or under water stress causes wilting. In many textbooks, ABA is linked to wilting because it reduces turgor via stomatal closure. However, note: wilting is primarily due to water loss; ABA is released to combat it, but excessive ABA can be correlated. Among options, ABA is correct.
Q27. One limitation of electrical impulses is that:
Cells need time to resetAfter an electrical impulse (action potential), neurons and muscle cells enter a refractory period during which they cannot fire again immediately – they need time to reset. Impulses do not last forever, do not reach all cells (only connected ones), and are fast, not slow.
Q28. Chemical communication can be:
Continuous and steadyHormonal signals can provide prolonged, continuous, and steady regulation (e.g., growth hormone, thyroxine). Unlike nerve impulses which are discrete, hormones can maintain long‑term states. They are not only temporary, one‑time, or random.
Q29. Hormones act on:
Target organsHormones are specific; they bind to receptors on or in specific target cells (target organs). They do not act on all cells equally, nor only on bones or skin. For example, insulin acts on liver, muscle, and fat cells.
Q30. Adrenaline causes the heart to:
Beat fasterAdrenaline increases heart rate (positive chronotropy) and force of contraction to prepare the body for emergency. It does not stop or slow the heart, nor cause it to shrink.
Q31. Plant hormones are synthesised:
Away from the place of actionPlant hormones are often synthesised in one part (e.g., auxin in shoot tip) and transported to another part where they act. This is similar to animal hormones. They are not necessarily synthesised at the place of action, nor only in leaves or roots.
Q32. Higher concentration of auxin causes cells to:
Grow longerAuxin promotes cell elongation in shoots. At moderate concentrations, it stimulates growth; very high concentrations can inhibit growth or cause damage, but the general effect (especially in tropisms) is elongation. Breaking, stopping, or shrinking are not typical effects of higher auxin in shoots.
Q33. Growth of pollen tubes towards ovules is an example of:
ChemotropismPollen tubes grow toward chemicals (calcium, specific proteins) released by the ovule – a growth response to chemical stimuli, i.e., chemotropism. Hydrotropism (water), geotropism (gravity), phototropism (light) are not involved here.
Q34. Breathing rate increases due to contraction of:
Diaphragm and rib musclesBreathing (ventilation) is driven by the diaphragm and intercostal (rib) muscles. Their contraction increases thoracic volume, drawing air in. Increased breathing rate during fear or exercise is caused by faster contractions of these muscles. Stomach, arm, and heart muscles are not directly responsible.
Q35. Control and coordination in organisms is achieved by:
Nervous and endocrine systemsBoth systems work together: the nervous system provides rapid, short‑lived control, and the endocrine system provides slower, long‑lasting coordination. Muscles are effectors, not controllers. Neither system alone achieves full control and coordination.
Q36. Chemical communication works through:
Diffusion of chemicalsChemical communication (hormones) relies on the diffusion (or bulk flow via blood) of chemical messengers to target cells. It does not use bones, nerves only (though nerves can release neurotransmitters locally), or muscles. Diffusion is key.
Q37. Hormonal coordination in animals works:
Through blood circulationEndocrine hormones are secreted into the bloodstream and carried to distant target organs. They do not work only locally (that’s paracrine), nor through nerves only, nor independently of blood (most hormones travel via blood). Blood circulation is essential.
Q38. Gibberellins mainly help in:
Stem growthGibberellins promote stem elongation, seed germination, and fruit growth. They do not cause leaf fall (abscisic acid/ethylene), wilting (water deficit), or inhibit growth – they stimulate it.
Q39. The fastest means of information transmission is:
Electrical impulsesElectrical impulses along neurons travel at speeds up to 100 m/s – much faster than hormonal flow (via blood, cm/s) or simple chemical diffusion. Cell growth is extremely slow. Thus, electrical impulses are fastest.
Q40. Preparation for danger requires:
Integration of many tissuesThe fight‑or‑flight response involves the brain, nerves, adrenal glands, heart, lungs, muscles, blood vessels, etc. Integration of many tissues is essential. Only muscles or one tissue cannot produce the full response, and coordination is required.
Q41. Chemical signalling is useful because it:
Reaches all cellsHormones are distributed via the bloodstream, so they can reach all cells, although only target cells respond. This broad reach is a key advantage over nerve impulses, which are limited to connected cells. Chemical signalling is not instant, does not stop growth generally, and does not reach only nerves.
Q42. Controlled movements in organisms can be:
Either slow or fastMovements can be fast (e.g., reflex, voluntary quick actions) or slow (e.g., growth movements in plants, smooth muscle contractions). They are not restricted to one speed. Controlled movements encompass both.
Q43. Movement of sensitive plant leaves is:
Very quickMimosa leaves fold in seconds – very quick for a plant. It is not directional growth (it is a nastic movement independent of stimulus direction) and not growth‑based (uses turgor pressure). Quick is correct.
Q44. Chemotropism is a growth response to:
Chemicals“Chemo” refers to chemicals. Chemotropism is growth toward or away from chemical stimuli (e.g., pollen tube toward ovule). Water (hydrotropism), light (phototropism), gravity (geotropism) are different.
Q45. Cells cannot continuously transmit impulses because:
They need recovery timeAfter an action potential, the refractory period (recovery time) prevents continuous firing without a break. Energy is restored quickly, but the need for repolarization and resetting ion gradients causes a brief non‑responsive period. This is the correct limitation.
Q46. Cytokinins promote:
Cell divisionCytokinins stimulate cytokinesis (cell division) in plant tissues, especially in roots and shoots. They delay leaf fall (senescence), prevent cell death, and do not primarily cause cell elongation (auxin does). Cell division is their hallmark.
Q47. Chemical signals can reach:
All body cellsHormones circulate in the blood, so they can be delivered to every cell in the body. However, only cells with appropriate receptors respond. This is unlike nerve impulses, which reach only connected cells.
Q48. Bending of shoot towards light occurs because cells grow more on the:
Shady sideWhen light comes from one side, auxin moves to the shaded side, causing those cells to elongate more. This differential growth bends the shoot toward the light. The lighted side grows less; the shady side grows more.
Q49. Growth of roots downwards and shoots upwards is an example of:
GeotropismBoth root downward growth (positive geotropism) and shoot upward growth (negative geotropism) are responses to gravity – i.e., geotropism. Hydrotropism is water, chemotropism chemicals, phototropism light.
Q50. Sunflower movement in response to day and night is:
Quite slowSunflowers (young plants) exhibit heliotropism – tracking the sun across the sky. This movement is due to growth and turgor changes, taking hours – quite slow compared to animal movements, but not instant, very fast, or random. It is slow but observable.