All Free Biology MCQs with Answers

• A. CO2 cycle
• B. Nitrogen cycle
• C. Phosphorus cycle
• D. All of the above

Explanation: Bacteria are indispensable in various biogeochemical cycles. In the carbon cycle, they decompose organic matter, releasing carbon dioxide.

• A. Within nucleolus
• B. Prior to fission
• C. Just before transcription
• D. During S phase

Explanation: In bacteria, DNA replication occurs just prior to binary fission, ensuring that each daughter cell receives a complete set of genetic…

• A. It protects the bacterium from desiccation
• B. Provides pathogenicity to bacteria
• C. It allows bacterium to "hide" from host's immune system
• D. It allows the bacterium to attach to the surface
• E. All

Explanation: A bacterial capsule is advantageous to a bacterium, particularly in terms of pathogenicity, for the following reasons:1.

• A. It forms a bridge between two bacterial cells
• B. It involves the transport of genetic material via vectors
• C. It is a form of sexual reproduction
• D. None of these

Explanation: Bacterial conjugation is a mechanism of horizontal gene transfer where genetic material, typically plasmid DNA, is directly transferred…

• A. Choanoflagellates
• B. Trypanosoma
• C. Trichonymphas
• D. Paramecium

Explanation: Trypanosoma is a protozoan that causes African sleeping sickness, transmitted by the tsetse fly.

• A. Chrysophyta
• B. Pyrophyta
• C. Rhodophyta
• D. Phaeophyta

Explanation: Pinnularia is part of the diatom group, which falls under the Chrysophyta division.

• A. E. coli
• B. Salmonella
• C. Entamoeba histolytica
• D. Bacteroides fragilis
• E. Listeria monocytogenes

Explanation: This protozoan parasite is the correct answer. It is known to cause amoebic dysentery, a severe intestinal infection leading to diarrhea…

• A. Headache
• B. Muscular pains
• C. Constipation
• D. Chills

Explanation: Constipation is not typically associated with malaria. Malaria symptoms mainly include fever, chills, headache, and muscle pain.

• A. Bacterium
• B. Virus
• C. Fungus
• D. Alga

Explanation: Chlorella is a genus of freshwater green algae. It is a photosynthetic microorganism and belongs to the group of algae, specifically green…

• A. They move by forming specialized cytoplasmic projections called pseudopodia
• B. They have rigid cell wall
• C. They are multicellular organisms
• D. They are autotrophic

Explanation: Amoeba is a unicellular, heterotrophic organism without a rigid cell wall. It moves and captures food by extending pseudopodia (false feet).

• A. It ingests bacteria, yeasts, spores and decaying organic matter
• B. Form resistant haploid spores
• C. Undergoes meiosis
• D. Their zygote produces a single nucleated plasmodium

Explanation: Slime molds form diploid spores, not resistant haploid ones.

• A. Always viewed with a light microscope
• B. An enzyme-nucleus mixture
• C. Obligate, intracellular parasites
• D. Cellular
• E. Host independent

Explanation: Viruses are obligate, intracellular parasites, which means they require a host cell to reproduce and carry out their life cycle.

• A. Protista
• B. Monera
• C. Metazoa
• D. Animalia
• E. Bryophyta

Explanation: Kingdom Protista has membrane-bound organelles, as shown in the diagram and a true nucleus. That is why option A is correct

• A. Algae increase the level of dissolved oxygen in the immediate environment
• B. Algin is obtained from red algae and carrageenan from brown algae
• C. Agar­-agar is obtained from Gelidium and Gracilaria
• D. Laminaria and Sargassum are used as food

Explanation: (b) : Alginic acid is obtained from brown algae whereas carrageenan is obtained from red algae.

• A. Chlorella and Spirulina are used as space food
• B. Mannitol is stored food in red algae
• C. Algin and carrageenan are products of algae
• D. Agar­agar is obtained from Gelidium and Gracilaria

Explanation: (b) : Laminarin and mannitol are food reserves of brown algae or Phaeophyceae.

• A. They move by forming specialized cytoplasmic projections called pseudopodia
• B. They have a rigid cell wall
• C. They are multicellular organisms
• D. They are autotrophic

Explanation: This is the correct answer. Amoebas are single-celled organisms that move by extending and retracting temporary, finger-like projections…

• A. Unicellular organisms only
• B. Filamentous organisms only
• C. Huge multicellular organisms only
• D. Simple Acellular organisms
• E. Ranges from unicellular to Filaments to huge multicellular organisms

Explanation: Algae can be unicellular (existing as individual cells), colonial (several to many cells living in a colony), filamentous (several to many…

• A. Amoeba
• B. Radiolarians
• C. Forams
• D. Female Anopheles mosquito

Explanation: The female Anopheles mosquito is the correct answer because it acts as the vector for Plasmodium, the parasite that causes malaria.

• A. Uninucleated
• B. Enucleate
• C. Mononucleated
• D. Multinucleated

Explanation: The plasmodium of slime molds is an amoeboid mass of cytoplasm that is multinucleated, meaning it contains many nuclei within a single…

• A. Exhibit solely animal-like characteristics
• B. Exhibit solely plant-like characteristics
• C. Exhibit both animal and plant-like characteristics
• D. Exhibit characteristics typical of bacteria
• E. Exhibit characteristics typical of viruses

Explanation: Euglena is a protist that uniquely combines traits of both plants and animals.