All Free Biology MCQs with Answers

• A. Opens partially
• B. Closes completely
• C. Opens completely
• D. Remains unchanged

Explanation: The correct answer is that the stomatal pore closes completely when sugar is converted into starch in guard cells.

• A. Two meters
• B. Five meters
• C. One meter
• D. Half meter

Explanation: The correct answer is "One meter". A rye plant less than one meter tall can develop branch roots with a combined length of over 600…

• A. 50% of vascular plants
• B. 70% of angiosperms
• C. 70% of gymnosperms
• D. 90% of angiosperms

Explanation: Answer is "90% of angiosperms"Explanation: Mycorrhizal fungi get sugar and shelter from the plant, and in exchange increase the plant's…

• A. 200 meters
• B. 400 feet
• C. 300 meters
• D. 500 feet

Explanation: The correct answer is "200 meters." Xylem water tension, a result of transpiration and the cohesive and adhesive properties of water, can…

• A. 100 times
• B. 200 times
• C. 300 times
• D. 150 times

Explanation: The correct answer is "200 times." During the process of imbibition, seeds absorb a significant amount of water, causing their volume to…

• A. Metabolism
• B. Respiration
• C. Photosynthesis
• D. Vernalization

Explanation: The correct answer is Photosynthesis. During photosynthesis, plants use about 1% of the absorbed water to convert carbon dioxide and light…

• A. Cuticular transpiration
• B. Stomatal transpiration
• C. Lenticular transpiration
• D. None of these

Explanation: The correct answer is Lenticular transpiration. This type of transpiration occurs through lenticels, which are unique to woody plants and…

• A. Gibberellins
• B. Ethylene
• C. Abscisic acid
• D. Cytokinins

Explanation: The correct answer is Abscisic acid. Abscisic acid (ABA) is a plant hormone that plays a critical role in regulating the closure of…

• A. Increased
• B. Does not change
• C. Decreased
• D. First increased and then decreased

Explanation: The correct answer is "Decreased." When leaves transpire, they lose water vapor, which decreases the water potential of the mesophyll…

• A. 1 meter/8 years
• B. 1 meter/day
• C. 1 meter/hour
• D. 20 cm/min

Explanation: The correct answer is "1 meter/hour" because studies have shown that the average velocity of sugar transport in the phloem is…

• A. Capillarity
• B. Role of atmospheric pressure
• C. Pulsating action of living cells
• D. Transpiration cohesion theory of Dixon

Explanation: The transpiration cohesion theory states that water molecules in the xylem of a tree are held together by cohesion, or the attraction…

• A. Gibberellins, Leaf fall
• B. Cytokinin, Cell division
• C. IAA, Cell wall elongation
• D. Abscissic acid, Stomatal closure

Explanation: Gibberellins promote leaf growth and fruit growth and sometimes can induce parthenocarpy.

• A. It releases wound hormones.
• B. It induces the differentiation of new shoots
• C. It frees axillary buds from apical dominance.
• D. The apical shoot grows faster after pruning.

Explanation: (c) : Prunning is the process of cutting shoot tips to promote lateral growth of branches.

• A. Meristems
• B. Epistcms
• C. Peristems
• D. Mesostems
• E. Cyclostems

Explanation: "The explanation for this question will be added soon!".

• A. 5°C to 10°C
• B. 10°C to 15°C
• C. 18°C to 28°C
• D. 28°C to 30°C
• E. 25°C to 37°C

Explanation: Most of the enzyme work optimally in between 25°C to 37°C. Many enzymes work optimally within a specific temperature range, typically…

• A. Acetic Acid
• B. Ethyl Acetic Acid
• C. Methyl acetic Acid
• D. Indole Acetic Acid
• E. None of these

Explanation: Plant hormone "AUXIN" is indole Acetic Acid. Indole-3-acetic acid (IAA) is a naturally occurring plant hormone and a member of the auxin…

• A. Inhibitory Effects
• B. Compensatory Effects
• C. Compression Effects
• D. Comprehension Effect
• E. Conversion Effects

Explanation: The removal of apex releases the lateral buds from apical dominance is called compensatory Effects.

• A. Potassium excretion
• B. Sodium retention
• C. Water loss
• D. Urea excretion

Explanation: Aldosterone stimulates sodium reabsorption in DCT and collecting duct.

• A. Abdominal aorta (the large artery supplying blood to the body)
• B. Renal vein (carries oxygenated blood away from the kidney)
• C. Ureter (transports urine from kidney to urinary bladder)
• D. Inferior vena cava (large vein returning blood to the heart)

Explanation: A is the adrenal gland secreting adrenaline and noradrenaline for quick energy.

• A. Heterotherm
• B. Poikilotherm
• C. Ectotherm
• D. Endotherm

Explanation: A heterotherm is an organism that can regulate its body temperature, but not to a constant level.