All Free Biology MCQs with Answers

2611. The infective stage of malarial parasite, Plasmodium that enters human body is

• A. Merozoite
• B. Sporozoite
• C. Trophozoite
• D. Minuta form

Explanation: Sporozoites are the form of Plasmodium that is transmitted to humans through the bite of an infected female Anopheles mosquito. When the mosquito feeds on an infected human, it ingests the sexual forms of the parasite, which then develop into sporozoites within the mosquito's salivary glands. Sporozoites are injected into the human bloodstream during a mosquito bite and travel to the liver, where they infect liver cells to initiate the liver stage of the malaria life cycle.

2612. The main difference in Gram (+)ve and Gram (-)ve bacteria resides in their

• A. Cell wall
• B. Cell membrane
• C. Cytoplasm
• D. Flagella

Explanation: Gram-positive bacteria have a thick layer of peptidoglycan in their cell wall, which retains the crystal violet stain used in the Gram staining technique. This thick peptidoglycan layer is responsible for giving them their characteristic purple color when viewed under a microscope. On the other hand, Gram-negative bacteria have a thinner layer of peptidoglycan and an additional outer membrane composed of lipopolysaccharides. The thinner peptidoglycan layer in Gram-negative bacteria does not retain the crystal violet stain, and they appear pink when counterstained with safranin in the Gram staining process.

2613. Which one belongs to monera?

• A. Amoeba
• B. Escherichia
• C. Gelidium
• D. Spirogyra

Explanation: Escherichia belongs to the kingdom Monera, which is now considered an obsolete taxonomic classification. Monera used to include all prokaryotic organisms, including bacteria and cyanobacteria. Escherichia coli (E. coli) is a well-known bacterium and a member of the genus Escherichia.

2614. Absorptive heterotrophic nutrition is exhibited by

• A. Algae
• B. Fungi
• C. Bryophytes
• D. Pteridophytes

Explanation: Fungi are the correct answer. Fungi are classic examples of organisms that exhibit absorptive heterotrophic nutrition. They secrete enzymes that break down complex organic matter in their surroundings (such as decaying organic material or living organisms) into simpler forms, which they then absorb as nutrients. This process allows them to obtain energy and essential nutrients for their growth and survival. Option B is correct.

2615. System of classification used by Linnaeus was

• A. Natural system
• B. Artificial system
• C. Phylogenetic system
• D. Asexual system

Explanation: Linnaeus indeed proposed an artificial system of plant classification, which was based on specific morphological characters, especially sexual characters like the number of stamens, pistils, and other reproductive organs. This system is commonly referred to as the "sexual system" of plant classification.

2616. A bite of tsetse fly may pass to humans

• A. Leishmania donovani
• B. Trypanosoma gambiense
• C. Entamoeba histolytica
• D. Plasmodium vivax

Explanation: The correct option is B) Trypanosoma gambiense. A bite from the tsetse fly can transmit the parasite Trypanosoma gambiense to humans, causing a disease called African Trypanosomiasis, also known as sleeping sickness.

2617. Malaria fever coincides with liberation of

• A. Cryptomerozoties
• B. Metacryptomerozoites
• C. Merozoites
• D. Trophozoites

Explanation: Malaria fever coincides with the liberation of merozoites. Cryptomerozoites: Cryptomerozoites are dormant forms of the malaria parasite that reside in the liver cells of infected individuals. They can remain dormant for months or years before becoming active and causing infection. Metacryptomerozoites: Metacryptomerozoites are immature forms of the malaria parasite that develop from cryptomerozoites. They are released from the liver cells and invade red blood cells. Merozoites: Merozoites are actively dividing forms of the malaria parasite that reside in red blood cells. They multiply and eventually rupture the red blood cells, releasing new merozoites into the bloodstream. Trophozoites: Trophozoites are the feeding forms of the malaria parasite. They reside in red blood cells and consume the hemoglobin inside the cells.

2618. Trypanosoma belongs to class

• A. Sarcodina
• B. Zooflagellata
• C. Ciliata
• D. Sporozoa

Explanation: Trypanosoma belongs to the class Zooflagellata, which is a group of protozoa characterized by having flagella for movement in their active stages. Trypanosoma is a flagellated protozoan parasite responsible for causing diseases like African trypanosomiasis (also known as sleeping sickness) and Chagas disease.

2619. The vector for sleeping sickness is

• A. House fly
• B. Tsetse fly
• C. Sand fly
• D. Fruit fly

Explanation: The vector for sleeping sickness, also known as African trypanosomiasis, is the tsetse fly. Tsetse flies are large biting flies belonging to the genus Glossina, and they are the primary vectors responsible for transmitting the protozoan parasite Trypanosoma brucei, which causes sleeping sickness.

2620. Lichens indicate SO2 pollution because they

• A. Show association between algae and fungi
• B. Grow faster than others
• C. Are sensitive to SO2
• D. Flourish in SO2 rich environment

Explanation: Lichens are composite organisms formed through a mutualistic association between a fungus and an alga or a cyanobacterium. The alga or cyanobacterium provides food through photosynthesis, while the fungus provides a protective structure and absorbs water and nutrients.Lichens are highly sensitive to air pollution, especially sulfur dioxide (SO2) pollution. When SO2 is present in the air, it can be absorbed by the lichens along with other pollutants. The high sensitivity of lichens to SO2 makes them excellent bioindicators of air quality.As SO2 levels increase in the environment due to pollution, lichens become stressed and can even die off. So, the presence or absence of certain lichen species in an area can indicate the level of SO2 pollution. If lichens are thriving and diverse in an area, it suggests a cleaner, less polluted environment. On the other hand, if lichens are absent or limited in their diversity, it indicates higher levels of SO2 pollution in that region.