- Loss of water vapour from plant surface is called
(A) Respiration
(B) Transpiration
(C) Evaporation
(D) Excretion
ANSWER: Transpiration
Explanation:
Why (B) Transpiration is correct: Transpiration is the biological process by which plants lose water vapour, mainly through stomata in leaves.
Why the others are wrong: (A) Respiration is the metabolic process of releasing energy from food, not water loss. (C) Evaporation is a general physical process of liquid becoming vapour — transpiration is the biological equivalent and involves stomata and plant physiology. (D) Excretion is removal of metabolic wastes; transpiration is specifically water vapour loss.
- Water is lost mainly through
(A) Roots
(B) Stem
(C) Stomata
(D) Flowers
ANSWER: Stomata
Explanation:
Why (C) Stomata is correct: Stomata are tiny pores on leaf surfaces that provide the main pathway for water vapour exit.
Why the others are wrong: (A) Roots absorb water rather than lose it. (B) Stem has few structures for major water loss (some lenticels, but minimal). (D) Flowers contribute little to total transpiration compared to stomata on leaves.
- Water lost is replaced from
(A) Phloem
(B) Cortex
(C) Xylem
(D) Cambium
ANSWER: Xylem
Explanation:
Why (C) Xylem is correct: Xylem vessels transport water and dissolved minerals upward from roots to leaves to replace transpired water.
Why the others are wrong: (A) Phloem transports food (sugars), not bulk water. (B) Cortex is mainly storage/support tissue, not the main conducting tissue. (D) Cambium is meristematic tissue that produces xylem/phloem, not the transport pathway itself.
- Transpiration helps in
(A) Absorption of CO₂
(B) Cooling plant
(C) Food synthesis
(D) Seed formation
ANSWER: Cooling plant
Explanation:
Why (B) Cooling plant is correct: Evaporation of water from leaf surfaces removes heat, cooling the plant (evaporative cooling).
Why the others are wrong: (A) CO₂ absorption is by stomata for photosynthesis, not a primary role of transpiration. (C) Food synthesis occurs in chloroplasts (photosynthesis); transpiration indirectly aids transport but is not food synthesis. (D) Seed formation is a reproductive process unrelated to the primary role of transpiration.
- Evaporation from leaves causes
(A) Root pressure
(B) Transport of food
(C) Suction force
(D) Photosynthesis
ANSWER: Suction force
Explanation:
Why (C) Suction force is correct: Evaporation from the leaf surface creates a negative pressure (suction/transpiration pull) that draws water up through xylem.
Why the others are wrong: (A) Root pressure is a positive push from roots due to osmotic uptake — it’s different and usually weaker than transpiration pull. (B) Transport of food occurs in phloem (translocation), not caused by leaf evaporation. (D) Photosynthesis is light-driven synthesis of food, not caused by evaporation.
- Pull created by evaporation is
(A) Transpiration pull
(B) Root pressure
(C) Osmotic pull
(D) Capillary action
ANSWER: Transpiration pull
Explanation:
Why (A) Transpiration pull is correct: The pull generated by water evaporation at leaf surfaces that pulls water up xylem is called transpiration pull.
Why the others are wrong: (B) Root pressure is a push from roots, not the pull from leaves. (C) Osmotic pull refers to movement due to osmotic gradients but is not the standard term for the evaporation-generated pull. (D) Capillary action helps a bit in narrow vessels but is far weaker and not the main driving force in tall plants.
- Root pressure is more important
(A) Morning
(B) Evening
(C) Night
(D) Afternoon
ANSWER: Night
Explanation:
Why (C) Night is correct: At night transpiration is low (stomata often closed), so root pressure (osmotic push from roots) becomes relatively more significant for water movement.
Why the others are wrong: (A/B/D) During morning, evening, and especially afternoon, transpiration rates are higher and transpiration pull dominates over root pressure.
- Major driving force during daytime transport is
(A) Root pressure
(B) Gravity
(C) Osmosis
(D) Transpiration pull
ANSWER: Transpiration pull
Explanation:
Why (D) Transpiration pull is correct: In daytime, evaporation from leaves is high, creating the major suction that pulls water upward.
Why the others are wrong: (A) Root pressure is relatively minor daytime. (B) Gravity opposes upward movement rather than driving it. (C) Osmosis plays a role at cellular level but is not the main long-distance driving force during the day.
- Transpiration occurs mostly from
(A) Roots
(B) Leaves
(C) Stem
(D) Flowers
ANSWER: Leaves
Explanation:
Why (B) Leaves is correct: Leaves have the highest density of stomata, so most water loss occurs there.
Why the others are wrong: (A) Roots primarily absorb water. (C) Stems lose little compared to leaves (some via lenticels). (D) Flowers may lose some but not the majority.
- Transpiration also helps in
(A) Heating
(B) Cooling
(C) Respiration
(D) Growth only
ANSWER: Cooling
Explanation:
Why (B) Cooling is correct: Evaporative water loss lowers leaf temperature and prevents overheating.
Why the others are wrong: (A) Heating is the opposite. (C) Respiration is metabolic energy release, unrelated to the cooling effect. (D) Growth involves many factors; transpiration contributes indirectly but its direct effect is cooling.
TRANSPORT OF FOOD IN PLANTS
- Transport of food is called
(A) Diffusion
(B) Translocation
(C) Absorption
(D) Evaporation
ANSWER: Translocation
Explanation:
Why (B) Translocation is correct: Translocation is the specific term for movement of sugars and other organic solutes in the phloem.
Why the others are wrong: (A) Diffusion is passive, short-distance movement; not the organized long-distance transport in plants. (C) Absorption is uptake into cells/tissues, not long-distance transport. (D) Evaporation is loss of water, unrelated.
- Food is transported through
(A) Xylem
(B) Phloem
(C) Cortex
(D) Pith
ANSWER: Phloem
Explanation:
Why (B) Phloem is correct: Phloem tissue conducts organic nutrients (sugars, amino acids) from source to sink.
Why the others are wrong: (A) Xylem carries water and minerals upward. (C/D) Cortex and pith are primarily storage/support tissues, not the primary conducting tissue for food.
- Food movement occurs in
(A) Vessels
(B) Tracheids
(C) Sieve tubes
(D) Fibres
ANSWER: Sieve tubes
Explanation:
Why (C) Sieve tubes is correct: Sieve tube elements are the specialized phloem cells through which translocation occurs.
Why the others are wrong: (A) Vessels and (B) tracheids are xylem elements for water transport. (D) Fibres are supportive cells, not conduits for food.
- Helper cells in phloem are
(A) Guard cells
(B) Companion cells
(C) Root cells
(D) Xylem cells
ANSWER: Companion cells
Explanation:
Why (B) Companion cells is correct: Companion cells are metabolically active cells adjacent to sieve tubes that assist with loading/unloading of sugars and provide ATP.
Why the others are wrong: (A) Guard cells control stomata, not phloem transport. (C) Root cells are generic; not specific helper cells of phloem. (D) Xylem cells are part of water-conducting tissue, not helpers for phloem.
- Phloem movement is
(A) Only upward
(B) Only downward
(C) Both directions
(D) Circular
ANSWER: Both directions
Explanation:
Why (C) Both directions is correct: Phloem translocation is bidirectional — nutrients move from sources (leaves) to various sinks (roots, fruits, growing tissues) as needed.
Why the others are wrong: (A/B) Limiting to one direction is incorrect because sinks can be above or below sources. (D) “Circular” is not a correct description of the mechanism.
- Unlike xylem, phloem transport uses
(A) Pressure only
(B) Gravity only
(C) ATP energy
(D) Diffusion only
ANSWER: ATP energy
Explanation:
Why (C) ATP energy is correct: Phloem loading/unloading is active, requiring metabolic energy (ATP) for concentration gradients.
Why the others are wrong: (A) Pressure is part of the pressure-flow mechanism but energy is needed to create gradients. (B) Gravity does not drive phloem flow. (D) Diffusion alone cannot account for long-distance, directional phloem transport.
- Sugar enters phloem using
(A) Light
(B) ATP
(C) Osmosis
(D) Gravity
ANSWER: ATP
Explanation:
Why (B) ATP is correct: Sugars are actively loaded into phloem sieve tubes via energy-dependent transporters using ATP.
Why the others are wrong: (A) Light drives photosynthesis but not the loading mechanism directly. (C) Osmosis moves water, not actively transport sugar molecules into phloem. (D) Gravity is irrelevant for active loading.
- Movement in phloem occurs due to
(A) Pressure difference
(B) Heat
(C) Wind
(D) Temperature
ANSWER: Pressure difference
Explanation:
Why (A) Pressure difference is correct: The pressure-flow hypothesis explains phloem movement as flow from high pressure (source) to low pressure (sink).
Why the others are wrong: (B/C/D) Heat, wind, and temperature are not the primary mechanistic drivers of phloem flow.
- Spring season food is transported to
(A) Roots
(B) Leaves
(C) Buds
(D) Fruits
ANSWER: Buds
Explanation:
Why (C) Buds is correct: In spring, dormant buds need resources to develop into leaves and flowers, so translocation is directed to buds.
Why the others are wrong: (A) Roots are storage sinks but early growth priority is buds. (B) Leaves are developing from buds — the food goes to buds/young leaves. (D) Fruits form later, not the primary spring sink.
- Phloem transports
(A) Oxygen
(B) Amino acids
(C) Water only
(D) Minerals
ANSWER: Amino acids
Explanation:
Why (B) Amino acids is correct: Phloem carries organic solutes: sugars, amino acids, hormones — all part of the transported food.
Why the others are wrong: (A) Oxygen is a gas exchanged by stomata and carried in animals by blood, not phloem’s role. (C) Water is mainly transported by xylem, though water also moves with phloem sap. (D) Minerals are primarily moved in xylem from roots.
EXCRETION
- Removal of waste is called
(A) Respiration
(B) Digestion
(C) Excretion
(D) Circulation
ANSWER: Excretion
Explanation:
Why (C) Excretion is correct: Excretion specifically refers to removal of metabolic waste products from organisms.
Why the others are wrong: (A) Respiration releases energy; (B) Digestion breaks down food; (D) Circulation transports substances — none define waste removal.
- Unicellular organisms remove wastes by
(A) Breathing
(B) Excretion organs
(C) Diffusion
(D) Osmosis
ANSWER: Diffusion
Explanation:
Why (C) Diffusion is correct: Single-celled organisms exchange gases and remove soluble wastes directly across their cell membrane by diffusion.
Why the others are wrong: (A) “Breathing” implies specialized organs; unicells lack them. (B) No excretory organs exist in unicellular life. (D) Osmosis is movement of water across a membrane, not the primary method for removal of metabolic wastes.
- Human excretory system contains
(A) Lungs
(B) Heart
(C) Kidneys
(D) Liver
ANSWER: Kidneys
Explanation:
Why (C) Kidneys is correct: Kidneys are the primary organs that filter blood and excrete nitrogenous wastes as urine.
Why the others are wrong: (A) Lungs expel CO₂ and some water vapour but aren’t the full excretory system. (B) Heart circulates blood, not excrete. (D) Liver metabolizes toxins and produces urea but is not the main excretory organ.
- Units of kidney are
(A) Alveoli
(B) Nephron
(C) Lobule
(D) Duct
ANSWER: Nephron
Explanation:
Why (B) Nephron is correct: Each kidney contains many nephrons — the microscopic functional units that filter blood and form urine.
Why the others are wrong: (A) Alveoli are lung air sacs. (C) Lobule is a term used for liver/lung structures but not the kidney functional unit. (D) Ducts are tubular passages but not the basic unit.
- Kidneys remove
(A) Oxygen
(B) Glucose
(C) Urea
(D) Fat
ANSWER: Urea
Explanation:
Why (C) Urea is correct: Urea is a water-soluble nitrogenous waste produced by protein breakdown and excreted by kidneys.
Why the others are wrong: (A) Oxygen is a gas exchanged by lungs. (B) Glucose is a valuable nutrient normally reabsorbed, not excreted. (D) Fat is not primarily excreted by the kidney.
- Urine passes from kidneys to bladder through
(A) Urethra
(B) Ureter
(C) Nephron
(D) Vena cava
ANSWER: Ureter
Explanation:
Why (B) Ureter is correct: Ureters are paired tubes that carry urine from each kidney to the urinary bladder.
Why the others are wrong: (A) Urethra carries urine from bladder to the outside. (C) Nephron makes urine but is not the transport duct. (D) Vena cava is a large vein returning blood to the heart.
- Urine is stored in
(A) Kidney
(B) Urethra
(C) Urinary bladder
(D) Ureter
ANSWER: Urinary bladder
Explanation:
Why (C) Urinary bladder is correct: The urinary bladder is the organ that stores urine until elimination.
Why the others are wrong: (A) Kidneys produce urine. (B) Urethra is the outlet tube. (D) Ureters transport urine but do not store it.
- Urine leaves body via
(A) Kidney
(B) Ureter
(C) Bladder
(D) Urethra
ANSWER: Urethra
Explanation:
Why (D) Urethra is correct: The urethra is the tube that allows urine to exit the body from the bladder.
Why the others are wrong: (A) Kidneys produce urine. (B) Ureters transport urine from kidney to bladder. (C) Bladder stores urine but is not the external exit.
- Filtration occurs in
(A) Tubules
(B) Capillaries of nephron
(C) Ureter
(D) Bladder
ANSWER: Capillaries of nephron
Explanation:
Why (B) Capillaries of nephron is correct: The glomerular capillaries in the nephron filter blood plasma into Bowman’s capsule — the primary filtration site.
Why the others are wrong: (A) Tubules are mainly for reabsorption and secretion. (C) Ureter transports urine. (D) Bladder stores urine.
- Nephron filters wastes from
(A) Plasma
(B) Water
(C) Blood
(D) Oxygen
ANSWER: Blood
Explanation:
Why (C) Blood is correct: Nephrons filter waste products out of the blood (plasma filtered is part of blood), removing urea and excess ions.
Why the others are wrong: (A) Plasma is the fluid component of blood — technically filtration is of plasma, but the conventional answer is blood as the source. (B) Water is a component but the nephron filters the blood, not water alone. (D) Oxygen is not a waste and is not what nephrons filter out.
- Reabsorption includes
(A) Waste only
(B) Water, salts, glucose
(C) Oxygen
(D) CO₂
ANSWER: Water, salts, glucose
Explanation:
Why (B) Water, salts, glucose is correct: After filtration, useful substances (water, ions, glucose) are reabsorbed from nephron tubules back into the blood.
Why the others are wrong: (A) Wastes are generally not reabsorbed. (C/D) Gases like oxygen and CO₂ are handled by respiration/gas exchange, not by tubular reabsorption in the kidney.
- Water reabsorption depends on
(A) Time
(B) Temperature
(C) Body needs
(D) Light
ANSWER: Body needs
Explanation:
Why (C) Body needs is correct: The kidney adjusts reabsorption according to hydration status and physiological demands to maintain internal balance.
Why the others are wrong: (A) Time of day can influence but is not primary. (B) Temperature has minor effect. (D) Light has no direct role in renal water reabsorption.
- Bladder control is
(A) Automatic only
(B) Hormonal
(C) Nervous
(D) Chemical
ANSWER: Nervous
Explanation:
Why (C) Nervous is correct: Urination is controlled by neural reflexes and voluntary nervous control (brain and spinal cord).
Why the others are wrong: (A) Not purely automatic in adults — voluntary control exists. (B) Hormones modulate kidney function but bladder control is neural. (D) Chemical control isn’t the mechanism for bladder emptying.
- Kidney failure causes
(A) Dengue
(B) Waste accumulation
(C) Fever
(D) Anaemia
ANSWER: Waste accumulation
Explanation:
Why (B) Waste accumulation is correct: When kidneys fail, metabolic wastes (like urea) accumulate in the blood causing toxicity.
Why the others are wrong: (A) Dengue is a viral infection unrelated to kidney failure. (C) Fever may be a symptom but not defining. (D) Anaemia can be associated with chronic kidney disease but is not the direct, immediate result defined by failure — the primary consequence is waste buildup.
- Artificial kidney works by
(A) Filtration
(B) Osmosis
(C) Diffusion
(D) Respiration
ANSWER: Diffusion
Explanation:
Why (C) Diffusion is correct: Dialysis (artificial kidney) removes wastes from blood by diffusion across a semipermeable membrane into dialysis fluid.
Why the others are wrong: (A) Filtration is a kidney process but dialysis mainly relies on diffusion (and some ultrafiltration) rather than biological filtration. (B) Osmosis plays a role for water movement but diffusion is the core mechanism for solute removal. (D) Respiration is unrelated.
- Dialysing fluid lacks
(A) Glucose
(B) Urea
(C) Oxygen
(D) Water
ANSWER: Urea
Explanation:
Why (B) Urea is correct: The dialysing fluid is formulated without urea so urea diffuses from the blood into the fluid, removing it.
Why the others are wrong: (A) Glucose may be present in balanced amount to avoid blood sugar loss. (C) Oxygen is not the key solute; dialysis regarding gas exchange is irrelevant. (D) Water is present in dialysis fluid to allow osmotic balance and ultrafiltration.
- Dialysis does not involve
(A) Filtration
(B) Reabsorption
(C) Diffusion
(D) Purification
ANSWER: Reabsorption
Explanation:
Why (B) Reabsorption is correct (i.e., dialysis does not involve it): Dialysis removes wastes by diffusion/filtration but does not perform selective reabsorption of useful substances back into blood like kidneys do.
Why the others are wrong: (A) Filtration/ (C) Diffusion are the working principles of dialysis. (D) Purification is the goal/result of dialysis.
- Initial kidney filtrate is about
(A) 1 L/day
(B) 5 L/day
(C) 180 L/day
(D) 500 L/day
ANSWER: 180 L/day
Explanation:
Why (C) 180 L/day is correct: The glomerular filtration rate produces roughly 180 litres of filtrate daily in an average adult before reabsorption.
Why the others are wrong: (A/B) 1–5 L are too low and correspond more to final urine or blood plasma volumes; (D) 500 L/day is far above physiological reality.
- Actual urine output per day is
(A) 50 L
(B) 180 L
(C) 1–2 L
(D) 10 L
ANSWER: 1–2 L
Explanation:
Why (C) 1–2 L is correct: After massive reabsorption, the typical adult produces about 1–2 litres of urine daily.
Why the others are wrong: (A) 50 L is impossible; (B) 180 L is initial filtrate before reabsorption; (D) 10 L is excessive and not normal.
EXCRETION IN PLANTS
- Oxygen is a waste from
(A) Respiration
(B) Transpiration
(C) Photosynthesis
(D) Excretion
ANSWER: Photosynthesis
Explanation:
Why (C) Photosynthesis is correct: Oxygen is produced as a by-product of photosynthesis when water is split; for many plants it is surplus and effectively a waste product.
Why the others are wrong: (A) Respiration consumes oxygen rather than producing it. (B) Transpiration is water vapour loss. (D) Excretion is general waste removal — photosynthesis specifically produces O₂.
- Extra water is removed by
(A) Respiration
(B) Transpiration
(C) Transport
(D) Photosynthesis
ANSWER: Transpiration
Explanation:
Why (B) Transpiration is correct: Transpiration is the main mechanism by which plants remove excess water via evaporation from stomata.
Why the others are wrong: (A) Respiration is metabolic; (C) Transport moves water around but doesn’t remove excess to the atmosphere; (D) Photosynthesis consumes water in reactions but doesn’t remove excess.
- Plant wastes are stored in
(A) Roots
(B) Leaves
(C) Vacuoles
(D) Wood
ANSWER: Vacuoles
Explanation:
Why (C) Vacuoles is correct: Vacuoles in plant cells often sequester toxic or waste substances to isolate them from the rest of the cell.
Why the others are wrong: (A/B/D) Roots, leaves, and wood can store some wastes at tissue/organ level, but the cellular storage site specifically is the vacuole.
- Gums and resins are stored in
(A) Phloem
(B) Xylem
(C) Old xylem
(D) Roots
ANSWER: Old xylem
Explanation:
Why (C) Old xylem is correct: Gums and resins accumulate in the heartwood/old xylem (dead xylem) where they are sequestered.
Why the others are wrong: (A) Phloem is active food transport tissue, not main resin store. (B) Active xylem (sapwood) transports water — storage of resins occurs in older, dead xylem. (D) Roots may store some substances but resins/gums are characteristic of old xylem.
- Plants remove waste by
(A) Leaves falling
(B) Roots only
(C) Stomata only
(D) Bark only
ANSWER: Leaves falling
Explanation:
Why (A) Leaves falling is correct: Plants accumulate certain wastes in leaves and remove them when these leaves abscise and fall.
Why the others are wrong: (B) Roots don’t “remove” wastes by detachment. (C) Stomata release gases but not all wastes. (D) Bark can store or isolate wastes but leaf fall is a common removal mechanism.
- Some wastes are secreted into
(A) Air
(B) Water
(C) Soil
(D) Leaves
ANSWER: Soil
Explanation:
Why (C) Soil is correct: Roots can excrete certain substances into surrounding soil (e.g., exudates, excess minerals).
Why the others are wrong: (A) Air is where gases like O₂ may be released, but many wastes are secreted into soil. (B) Water bodies may receive runoff but soil is the direct medium for root exudation. (D) Leaves store wastes but “secreting into leaves” is storage rather than secretion into an external medium.
- Plants do not use
(A) Kidneys
(B) Leaves
(C) Stem
(D) Roots
ANSWER: Kidneys
Explanation:
Why (A) Kidneys is correct: Plants lack specialized excretory organs such as kidneys — that is a key difference from animals.
Why the others are wrong: (B/C/D) Leaves, stems, and roots are structures plants do use for various functions including some waste storage/release.
- Wastes in plants are mostly
(A) Urea
(B) Oxygen
(C) Resins
(D) Sweat
ANSWER: Resins
Explanation:
Why (C) Resins is correct: Plants commonly accumulate secondary metabolites like resins, gums, tannins as waste or inert products.
Why the others are wrong: (A) Urea is primarily an animal nitrogen waste. (B) Oxygen is a by-product of photosynthesis but not generally stored as waste. (D) Sweat is an animal excretory product.
- Plants store wastes mainly in
(A) Living parts
(B) Dead cells
(C) Seeds
(D) Flowers
ANSWER: Dead cells
Explanation:
Why (B) Dead cells is correct: Dead tissues (like old xylem, cork) provide safe compartments to store toxic substances without harming living cells.
Why the others are wrong: (A) Storing toxins in living parts would be harmful to metabolic activity. (C/D) Seeds and flowers are not primary long-term waste storage sites.
- Leaves contain waste and fall off because
(A) Growth
(B) Excretion
(C) Respiration
(D) Germination
ANSWER: Excretion
Explanation:
Why (B) Excretion is correct: One reason leaves are shed is that they accumulate wastes (or no longer needed products) and abscission removes those wastes from the plant body.
Why the others are wrong: (A) Growth can cause leaf shedding indirectly but is not the primary reason. (C) Respiration is metabolic; (D) Germination is seed sprouting, unrelated.
- Main difference from animals
(A) Kidneys absent
(B) Heart absent
(C) Blood absent
(D) Oxygen absent
ANSWER: Kidneys absent
Explanation:
Why (A) Kidneys absent is correct: Plants do not possess specialized excretory organs (like kidneys) — they use other strategies for waste handling, making this a key difference highlighted in excretion contexts.
Why the others are wrong: (B) Plants also lack a heart, but the question is framed within excretion context — “kidneys absent” is the specific excretory contrast. (C) Plants do have transport fluids (sap) though not blood as in animals; calling “blood absent” is less precise for excretion comparisons. (D) Oxygen absent is false — plants produce oxygen during photosynthesis.