All Free Biology MCQs with Answers

• A. 11:00 hours
• B. 15:00 hours
• C. 11 ½ Hours
• D. 15 ½ hours

Explanation: Critical day length is the length of the light period in a 24-hour cycle required to inhibit the flowering of short-day plants.

• A. Abscisic acid
• B. Cytokinin
• C. Seisomonasty
• D. Demonasty

Explanation: Senescence is the aging of individual cells within an organism. The organism itself is still alive and metabolizing energy, but its cells…

• A. Shoot
• B. Flowers
• C. Leaves
• D. Base of the plant

Explanation: Auxin is a plant hormone that is primarily produced in the shoot tips and young leaves.

• A. Chlamydemonas
• B. Mimesa pudica
• C. Oxalis
• D. Crocus

Explanation: The locomotary movement of free swimming organisms or their organs in response to one-sided illumination is called phototaxis.

• A. Auxins
• B. Gibberellins
• C. Cytokinis
• D. Ethylene

Explanation: Ethylene is a gaseous plant hormone that helps regulate various processes in plants.

• A. Cellulose
• B. Cuticle
• C. Chitin
• D. Lignin

Explanation: Cellulose is a tough, fibrous, and water-insoluble polysaccharide that plays an integral role in keeping the structure of plant cell walls…

• A. Red light
• B. Blue light
• C. Sunlight
• D. Green light

Explanation: Greenlight range spectrum is considered as least effective for the process of photosynthesis: The wavelength of green light is thought to…

• A. corymbs
• B. umbel
• C. catkin
• D. panicle

Explanation: The pedicel is a stalk or stem that supports a single flower. It connects the single flower to the inflorescence.

• A. Xylem
• B. Collenchyma
• C. Sclerenchyma
• D. Parenchyma

Explanation: Collenchyma is living tissue that provides support to the plant as it has extra cellulose deposited in its cell wall the cell wall is…

• A. Stomata are opened
• B. Day is humid
• C. Concentration of CO2 inside the leaf is high
• D. Concentration of O2 inside leaf is high

Explanation: Photorespiration occurs when Rubisco, an enzyme involved in photosynthesis, binds with O2 instead of CO2.

• A. Nepenthes
• B. Utricularia
• C. Dionea
• D. Sundew

Explanation: Drosera or sundew is a carnivorous plant found in moist, acidic, and nutrient-deficient soils.

• A. Sugar
• B. pH
• C. Potassium
• D. All of the above

Explanation: The opening and closing of stomata are primarily controlled by the conversion of starch to sugar and vice versa in guard cells.

• A. Xerophytes
• B. Mesophytes
• C. Halophytes
• D. Hydrophytes

Explanation: Mangroves are tropical plants that are adapted to lose, wet soils, salt water and being periodically submerged by tides

• A. Stoma of chloroplasts
• B. Granum of the chloroplast
• C. Cytoplasm of the cell
• D. ....

Explanation: Unlike the light reactions, which take place in the thylakoid membrane, the reactions of the Calvin cycle take place in the stroma, the…

• A. Lateral meristem
• B. Apical meristem
• C. Intercalary
• D. None

Explanation: The meristem responsible for wood formation in plants is the lateral meristem, specifically the vascular cambium and the cork cambium.

• A. Capillary rise of water
• B. Root pressure
• C. Tensile strength
• D. All of these

Explanation: Guttation is the process by which plants excrete excess water in the form of droplets through specialized structures called hydathodes.

• A. Increase in the soil nutrient
• B. More aeration of soil
• C. Soil fertility
• D. ....

Explanation: Crop rotation helps return nutrients to the soil without synthetic inputs.

• A. 3
• B. 5
• C. 6
• D. 7

Explanation: The ion crosses three main structures when moving from one cell to an adjacent cell in a woody plant:Middle Lamella: This is the…

• A. C55H70O6N4Mg
• B. C70H55O11N5Mg4
• C. C14H55O6N5Mg3
• D. C55H76O5N6Mg2

Explanation: The correct molecular formula of chlorophyll b is C55H70O6N4Mg. This formula indicates the presence of 55 carbon atoms, 70 hydrogen atoms…

• A. 6C14
• B. 1H2
• C. 2He4
• D. 6O16

Explanation: Oxygen-16 is the ideal isotope for studying photosynthesis because it allows for precise measurements of oxygen uptake and flow during the…