All Free Biology MCQs with Answers

1221. The part of chloroplast where CO2 is fixed to manufacture sugar is__________?

• A. Stroma
• B. Grana
• C. Thylakoid
• D. Outer membrane

Explanation: Carbon dioxide is fixed into carbohydrate during the Calvin cycle, which takes place in the chloroplast stroma. The stroma contains the enzymes needed for carbon fixation, whereas grana and thylakoids carry out the light-dependent reactions that provide ATP and NADPH. The likely mistake is choosing grana because they contain chlorophyll, but they do not directly fix CO2 into sugar.

1222. Movement of the material across the cell membrane which does not requiring expenditure of metabolic energy is called__________?

• A. Active transport
• B. Passive transport
• C. Co-transport
• D. Counter transport

Explanation: Passive transport moves substances across the membrane down their concentration or electrochemical gradient without ATP expenditure, including diffusion and osmosis. Students may choose active transport because it also moves substances across membranes, but active transport requires metabolic energy and commonly moves substances against a gradient.

1223. Percentage of proteins in cell membrane is____________?

• A. 20-40%
• B. 40-50%
• C. 60-80%
• D. 80-100%

Explanation: Membrane composition varies among cell types, but proteins commonly make up about 60 to 80 percent of the membrane's dry mass because they form channels, carriers, receptors and structural components. Students may choose 40 to 50 percent by recalling an approximate lipid percentage rather than the protein proportion.

1224. Who first observed and thus hypothesized that new cells are formed from previously existing living cell?

• A. Theodor Schwann and Schleiden
• B. Rudolph Virchows
• C. Louis Pasteur
• D. Both b and c

Explanation: Rudolf Virchow extended cell theory with the principle that every new cell arises from a pre-existing cell, expressed as omnis cellula e cellula. Louis Pasteur supported biogenesis by disproving spontaneous generation, but he did not formulate this cell-theory principle, so students may incorrectly choose d.

1225. Who coined the term CELL?

• A. Schwann
• B. Schleiden
• C. Robert Hook
• D. Both a and b

Explanation: Robert Hooke coined the term cell in 1665 after observing box-like compartments in cork under a microscope. Schleiden and Schwann later developed cell theory, so students may choose d by confusing the discoverer of the term with the scientists who proposed the theory.

1226. Animals of which class of arthropoda are present everywhere_____________?

• A. Crustacean
• B. Insecta
• C. Arachnida
• D. Myriapoda

Explanation: Insecta is the most widespread and diverse arthropod class, with members occupying nearly every terrestrial and freshwater habitat. Crustaceans, arachnids and myriapods are also widely distributed, but they are less ecologically ubiquitous, so students may choose arachnids because of their familiar global presence.

1227. How many spiracles are present in cockroach_____________?

• A. 5
• B. 10
• C. 20
• D. 40

Explanation: A cockroach has 10 pairs of spiracles, with two thoracic pairs and eight abdominal pairs. Therefore, 10 pairs x 2 spiracles per pair = 20 spiracles, so students who count pairs as individual openings may choose b.

1228. Double fertilization is feature of____________?

• A. Ferns
• B. Whisk ferns
• C. Gymnosperms
• D. Angiosperms

Explanation: In angiosperms, one male gamete fuses with the egg and the other fuses with the polar nuclei, producing the zygote and endosperm respectively. Students often choose gymnosperms because they are also seed-producing plants, but double fertilization is a defining feature of flowering plants.

1229. The single healthy megaspore retained within the megasporangium germinates to form an egg containing female gaemtophyte called______________?

• A. Ovule
• B. Seed
• C. Fruit
• D. Embroyo sac

Explanation: The surviving megaspore develops by mitotic divisions into the embryo sac, the female gametophyte of flowering plants, which contains the egg cell and other nuclei. Students may choose ovule because the embryo sac is located inside it, but the ovule is the whole structure, not the female gametophyte itself.

1230. Pollen grains in pinus have __________ for dispersal through wind?

• A. Flagella
• B. Cilia
• C. Wings
• D. Feathers

Explanation: Pinus pollen grains possess air sacs or wings that increase surface area and allow them to be carried efficiently by wind. Students may choose flagella because these structures aid movement in some cells, but wind-dispersed pollen is non-motile.