All Free Biology MCQs with Answers

1621. Which one of these is a set of useful insects?

• A. Sandfly , butterfly, hoeybee
• B. Sikmoth, honeybee, locust
• C. Honeybee, silkmoth, tsetse fly
• D. Honeybee , lac insect, cochineal insect

Explanation: Honeybees provide honey and wax, lac insects provide lac, and cochineal insects provide the red dye carmine, making this the set of useful insects. Students may choose the silkmoth set, but locusts are crop pests and tsetse flies transmit disease, so those sets contain harmful insects.

1622. A moth is closely related to_________?

• A. Wasp
• B. Beetle
• C. Cricket
• D. Butterfly

Explanation: Moths and butterflies both belong to the order Lepidoptera and share scaled wings and a coiled proboscis in the adult stage. Students may choose wasp because both are flying insects, but wasps belong to Hymenoptera and are not as closely related as butterflies.

1623. Which one of these is an insect?

• A. Mite
• B. Spider
• C. Moth
• D. Scorpion

Explanation: A moth is an insect because it has six jointed legs, three body regions, and an exoskeleton, and it belongs to Lepidoptera. Mites, spiders, and scorpions are arachnids, which characteristically have eight legs rather than six.

1624. Which of the following is not nocturnal?

• A. Bedbug
• B. Mosquito
• C. Butterfly
• D. Cockroach

Explanation: Butterflies are generally diurnal, meaning they are active during daylight, whereas bedbugs, mosquitoes, and cockroaches are commonly active at night. Students may choose mosquitoes because some species feed during the day, but nocturnal activity is the usual textbook description for mosquitoes in this comparison.

1625. The most important group of producers in marine ecosystem is of__________?

• A. Diatoms
• B. Euglenoids
• C. Dinoflagellates
• D. Brown algae

Explanation: Diatoms are major marine phytoplankton, so they carry out a very large share of photosynthesis and form the base of marine food chains. Dinoflagellates are also important producers, but students may choose them because some species form conspicuous blooms; blooms do not make them the most important overall group.

1626. Lime stone deposits are formed from__________?

• A. Zooflagellates
• B. Foraminferans
• C. Aetinopods
• D. Apicomplexans

Explanation: Foraminiferans have calcium carbonate shells, and the accumulated shells and remains of these organisms contribute substantially to limestone deposits. Actinopods may have mineral-like skeletons, but their deposits are not the main source referred to here.

1627. Of the following which one is not the characteristic of dinoflagellates?

• A. Most of them are unicellular
• B. They have blooms
• C. Their cells are often covered with shells of interlocking cellulose plates impregnated with calcium
• D. None of these

Explanation: Most dinoflagellates are unicellular and many produce blooms, while many have cellulose plates forming a theca. The statement about plates being impregnated with calcium is not a general characteristic, so option c is the exception; students may choose d if they overlook that calcium impregnation is inaccurate.

1628. Examples of Rhodophytes are___________?

• A. Chondrus
• B. Polysiphonia
• C. Both of these
• D. Pinnularia

Explanation: Chondrus and Polysiphonia are both red algae, or rhodophytes, containing red pigments such as phycoerythrin. Pinnularia is a diatom, so a student who selects d is confusing a brownish photosynthetic protist with a red alga.

1629. Which of the following statement about eiliates in incorrect_____________?

• A. Contain mainly unicellular organisms.
• B. Their contractile vacoule is respobsible for water regulation.
• C. They are even capable of sexual reproduction.
• D. Diploid nucleus being smaller is responsible for cells metabolism and growth while polyploidy nucleus functions in sexual process.Biological Sciences

Explanation: In ciliates, the diploid micronucleus is involved mainly in sexual reproduction, whereas the usually polyploid macronucleus controls metabolism, growth and everyday cell activities. Option d reverses these functions, so students may instead select b if they misunderstand that the contractile vacuole regulates water balance rather than respiration.

1630. Radiolarians belong to which of the following protozoal group____________?

• A. Zooflagellates
• B. Actinopods
• C. Foraminifera
• D. Apicomplexans

Explanation: Radiolarians are actinopods, characterized by fine, radiating axopodia supported by a central skeletal structure. Foraminiferans also have shells and pseudopodia, so their similar appearance can lead students to choose c.