All Free Biology MCQs with Answers

• A. Animal-like Protist
• B. Bacteria-like Protist
• C. Plant-like Protist
• D. Virus-like Protist
• E. Fungi-like Protist

Explanation: Slime molds are classified as fungi-like protists because they share some characteristics with fungi, such as the production of spores and…

• A. Both locomotory organelles and contractile vacuoles
• B. Locomotory organelles but not contractile vacuoles
• C. Contractile vacuoles but not locomotory organelles
• D. Neither locomotory organelle nor contractile vacuoles
• E. All are incorrect

Explanation: Sporozoans are a group of protists that are adapted to a parasitic lifestyle.

• A. Erythrocytic phase ⟶ Pre-erythrocytic phase ⟶ Gamogony ⟶ Post-erythrocytic phase
• B. Erythrocytic phase ⟶ Gamogony ⟶ Pre-erythrocytic phase ⟶ Post-erythrocytic phase
• C. Pre-erythrocytic phase ⟶ Post-erythrocytic phase ⟶ Gamogony ⟶ Erythrocytic phase
• D. Post-erythrocytic phase ⟶ Pre-erythrocytic phase ⟶ Erythrocytic phase ⟶ Gamogony
• E. Pre-erythrocytic phase ⟶ Erythrocytic phase ⟶ Post-erythrocytic phase ⟶ Gamogony

Explanation: The Plasmodium life cycle in humans starts with the pre-erythrocytic phase, where sporozoites infect liver cells and multiply.

• A. 6 - 8 sperm-like microgametes
• B. 6 - 8 sperm-like macrogametes
• C. 8 - 12 sperm-like microgametes
• D. 5 - 7 sperm-like macrogametes
• E. 12 - 15 sperm-like microgametes

Explanation: During the gametogony stage of the sexual cycle in certain protists, male gametocytes produce several flagellated microgametes, which are…

• A. 50% relative humidity is essential for sporangia production
• B. Sporangia cannot be produced if relative humidity exceeds 70%
• C. Sporangia are typically produced in a fully saturated atmosphere at temperatures between 25°C - 37°C
• D. The optimum temperature for producing sporangia is around 21°C
• E. Sporangia never form in their preferred environmental conditions

Explanation: The correct answer is Option D: 'The optimum temperature for the production of sporangia is 21°C'.

• A. Flagellata
• B. Sarcodina
• C. Sporozoa
• D. Ciliata
• E. Suctoria

Explanation: The correct answer is Ciliata. Balantidium and Opalina are ciliated protozoans, meaning they use cilia for movement and feeding, which is…

• A. 102°F
• B. 104°F
• C. 106°F
• D. 107°F
• E. 106°C

Explanation: Malaria can cause high fevers as part of its symptomatology, especially in severe cases.

• A. Headache
• B. Muscular pains
• C. Constipation
• D. Chills
• E. Flu-like symptoms

Explanation: Constipation is not a typical symptom of malaria. Malaria commonly presents with symptoms that affect the body's temperature regulation…

• A. The plant body is called thallus
• B. Sporophyte is thallus with 26 chromosomes
• C. Gametophyte is thallus with 26 chromosomes
• D. Reproduction is by sexual as well as asexual methods
• E. It is found growing along the sea-coasts between high and low tides.

Explanation: The correct answer is Option D: 'Reproduction is by sexual as well as asexual methods.' This statement is typically true for many algae…

• A. Yeast ­- Ethanol
• B. Streptomycetes ­- Antibiotic
• C. Coliforms ­- Vinegar
• D. Methanogens ­- Gobar gas

Explanation: Coliform bacteria are a commonly used bacterial indicator of the sanitary quality of foods and water.

• A. Streptomyces- Antibiotic
• B. Serratia-Drug addiction
• C. Spirulina Single-celll protein
• D. Rhizobium­-Biofertilizer

Explanation: Serratia marcescens is considered a harmful human pathogen that has been known to cause urinary tract infections, wound infections, and…

• A. The method is less effective as compared with the use of insecticides.
• B. The practical difficulty of introducing the predator to specific areas.
• C. The predator develops a preference to other diets and may itself become a pest.
• D. The predator does not always survive when transferred to a new environment.

Explanation: Insect enemies play an important role in nature for managing the phytophagous insect pests and keep a balance.

• A. Legumes fix nitrogen only through the specialized bacteria that live in their roots.
• B. Legumes fix nitrogen independently of the specialized bacteria that live in their roots.
• C. Legumes fix nitrogen only through specialized bacteria that live in their leaves.
• D. Legumes are incapable of fixing nitrogen.

Explanation: The nitrogen­-fixing ability of leguminous plants is not a property of the plants as such but results from infection of their roots by…

• A. Tendency of biological systems to change with change in the environment
• B. Tendency of biological systems to resist change
• C. Disturbance of self regulatory system and natural controls
• D. Biotic materials used in homeopathic medicines

Explanation: The ability to maintain a steady state within a constantly changing environment is essential for the survival of living systems.

• A. Aerenchyma-Opuntia
• B. Age pyramid-Biome
• C. Parthenium hysterophorus-Threat to biodiversity
• D. Stratification-Population

Explanation: Parthenium hysterophorus is commonly known as congress grass or carrot weed. It is a herbaceous annual plant of the Family Asteraceae.

• A. Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants.
• B. Cyanobacteria such as Anabaena and Nostoc are not important mobilizers of phosphates and for plant nutrition in soil.
• C. At present it is not possible to grow maize without chemical fertilizers.
• D. Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.

Explanation: Eutrophication is the excessive growth of algae, plants, and animals in water bodies due to nutrient enrichment, particularly with…

• A. Anabaena and Nostoc are capable of fixing nitrogen in a free­living state also
• B. Root nodule-forming nitrogen fixers live as aerobes under free­living conditions
• C. Phosphorus is a constituent of cell membranes, certain nucleic acids, and all proteins
• D. Nitrosomonas and nitrobacteria are chemo­ autotrophs

Explanation: Phosphorus is present in the plasma membrane in the form of a phospholipid bilayer.

• A. Robert Hook
• B. Robert Brown
• C. Gregor Mendel
• D. Charless Darwin

Explanation: Gregor Mendel established the basic laws of inheritance through controlled breeding experiments with pea plants, earning him the title…

• A. They are multinucleated
• B. They are 1-1 nm in diameter and surrounded by sarcolemma
• C. They contain O2 storing molecules called myoglobin
• D. Their cytoplasm contains a high concentration of carbohydrates

Explanation: Skeletal muscle fibres are not 1-1 nm in diameter. They are 10-100 micrometers in diameter and are surrounded by sarcolemma.

• A. Syphilis
• B. Gonorrhoea
• C. AIDS
• D. Herpes

Explanation: Syphilis is a sexually transmitted infectious (STI) disease caused by the bacterium Treponema pallidum.