Explanation

• Monotremes are mammals that lay eggs instead of giving birth to live young.
• The platypus and echidnas are the only living groups of monotremes.
• Placentals develop their young inside the uterus with the help of a placenta.
• Marsupials usually give birth to underdeveloped young that continue developing in a pouch.
• Cetacea includes whales, dolphins, and porpoises.

Last verified on 27-10-2026

Explanation

• The fourth ventricle is a fluid-filled cavity located in the hindbrain, between the brainstem and cerebellum.
• It lies behind the pons and upper medulla oblongata and in front of the cerebellum.
• It is continuous with the cerebral aqueduct above and the central canal of the spinal cord below.

Last verified on 27-10-2026

Explanation

• The biceps brachii contracts to bend the elbow joint, a movement called flexion.
• The triceps brachii performs the opposite movement, extending or straightening the elbow.
• The biceps and triceps work as an antagonistic pair: when one contracts, the other generally relaxes to allow movement.

Last verified on 27-10-2026

Explanation

• Exhaled air contains about 16% oxygen.
• Because the body absorbs some oxygen during gas exchange in the lungs.
• Atmospheric air contains approximately 21% oxygen.
• Exhaled air contains approximately 4% carbon dioxide, compared with about 0.04% in atmospheric air.

Last verified on 27-10-2026

Explanation

• The lingual vein drains blood from the tongue region in a frog and carries it toward the venous circulation.
• The cutaneous veins carry blood from the skin, which is important for cutaneous respiration in frogs.

Last verified on 27-10-2026

Explanation

• Thymine is a pyrimidine nitrogenous base found in DNA.
• But normally absent in RNA, where uracil takes its place.
• The two pyrimidine bases in RNA are uracil (U) and cytosine (C).
• Adenine (A) and guanine (G) are purine bases found in both DNA and RNA.
• DNA contains A, T, G, C.
• RNA contains A, U, G, C.

Last verified on 25-10-2026

Explanation

• N-formyl methionine (fMet) is the initiating amino acid in protein synthesis in bacteria, including E. coli.
• Chloroplasts and mitochondria have bacterial-like ribosomes and generally use fMet to initiate protein synthesis.
• Eukaryotic cytoplasmic ribosomes usually begin protein synthesis with ordinary methionine (Met), not formylated methionine.

Last verified on 01-11-2026

Explanation

• During DNA replication, helicase unwinds the double-stranded DNA.
• This unwinding creates tension and excessive twisting (supercoiling) ahead of the replication fork.
• Topoisomerases temporarily cut one or both DNA strands, allow the DNA to relax, and then rejoin the strands.
• DNA gyrase is a type of topoisomerase found in bacteria that helps remove positive supercoiling and introduces negative supercoiling.
• Topoisomerases prevent DNA tangling and help replication proceed smoothly.

Last verified on 01-11-2026

Explanation

• Mitochondria produce most of the ATP (adenosine triphosphate) in eukaryotic cells through aerobic cellular respiration.
• ATP is the main energy-carrying molecule of the cell.
• It provides energy for various cellular activities.

Additional information:

• ATP is also produced in the cytoplasm during glycolysis.
• In plant cells, chloroplasts also produce ATP during photosynthesis.
• It is mainly for use within the chloroplast.

Last verified on 27-10-2026

Explanation

• Quill feathers (flight feathers) are found on the wings and tail and provide lift, thrust, and steering.
• Contour feathers cover the bird’s body and give it a streamlined shape that reduces air resistance.

Last verified on 01-11-2026