Structural Organisation in Animals - Free MCQ Practice Test with solutions,

The correct answer is Option D - A: A-II, B-I, C-III, D-IV

Truncus arteriosus divides anteriorly into branches that form the right and left aortic arches, so it corresponds to II.

Pulmonary artery carries deoxygenated blood from the heart to the lungs for oxygenation, so it corresponds to I.

Sinus venosus collects venous blood from the body through precaval, postcaval and hepatic veins and hence receives blood from all parts of the body, corresponding to III.

Pulmonary vein returns oxygenated blood from the lungs to the heart, so it corresponds to IV.

All four individual correspondences are correct; therefore the given combination in Option D is consistent and correct.

Topic in NCERT: Heart anatomy

Line in NCERT: "heart is a muscular structure situated in the upper part of the body cavity. it has three chambers, two atria and one ventricle and is covered by a membrane called pericardium."

The correct answer is Option A - A-III, B-II, C-I, D-III

Cerebellum is part of the hindbrain and is mainly involved in the coordination of voluntary movements and maintenance of posture.

Optic lobes constitute the major portion of the midbrain and serve as the primary visual processing centres in frogs.

Olfactory lobes develop from the forebrain and are responsible for receiving and processing olfactory (smell) information.

Medulla oblongata belongs to the hindbrain and contains vital autonomic centres that regulate functions such as respiration and heart activity.

Topic in NCERT: Nervous system

Line in NCERT: "the brain is divided into fore-brain, mid-brain and hind-brain. forebrain includes olfactory lobes, paired cerebral hemispheres and unpaired diencephalon. the midbrain is characterised by a pair of optic lobes. hind-brain consists of cerebellum and medulla oblongata."

Option C is correct: The ureter acts as a urinogenital duct in males.

Sperm produced in the testes pass into the vasa efferentia, which open into the renal region; from there sperm enter the ureter and are carried to the cloaca.

Because the same duct conveys both urine and sperm, the ureter functions as a urinogenital duct in the male frog.

• Statement A is incorrect: the testes are actually paired structures lying close to the kidneys; the edited option that says they are unpaired is false.
• Statement B is incorrect: the vasa efferentia connect the testes to the renal region of the kidneys, not directly to the ureter.
• Statement D is incorrect: Bidder's canal is not a structure present only in males; the claim that it is male-only is false.

The correct answer is Option A - A: A-II, B-III, C-IV, D-I

Gizzard performs the grinding of food by strong muscular walls often with sclerotised teeth-like structures; this matches II.

Hepatic caecae secrete digestive juices/enzymes and increase the digestive surface, so their function is secretion of digestive enzymes, matching III.

Malpighian tubules are the excretory structures that remove nitrogenous wastes and help in osmoregulation; this corresponds to IV (excretion).

Ileum, as part of the posterior gut, is involved in the absorption of digested food (and reabsorption of water), therefore it corresponds to I.

Option A - A, B and C only is correct.

Cutaneous respiration occurs across the moist skin, which is highly vascularised and allows diffusion of oxygen and carbon dioxide; this contributes substantially to gas exchange in adult frogs.

Buccopharyngeal respiration takes place across the moist lining of the buccopharyngeal cavity; rhythmic movements of the floor of the mouth ventilate this surface and permit gas exchange in adults.

Pulmonary respiration is carried out by paired lungs; air is moved into the lungs by buccal pumping and gas exchange occurs across the lung surfaces in adult frogs.

Tracheal respiration through spiracles is not a mode of respiration in frogs; this mechanism is characteristic of many insects, so statement D is incorrect for adult frogs.

Branchial respiration using gills occurs in the larval tadpole stage and is lost during metamorphosis; therefore adult frogs do not perform branchial respiration and statement E does not apply to adults.

Thus only statements A, B and C are correct for the adult frog, matching Option A.

The correct answer is Option C - Supra-oesophageal ganglion and sub-oesophageal ganglion connected by circum-oesophageal connectives

• The supra-oesophageal ganglion is the dorsal brain region located above the oesophagus; it receives sensory input from the head appendages.
• The sub-oesophageal ganglion lies below the oesophagus and controls mouthparts and associated muscles.
• A pair of circum-oesophageal connectives runs around the oesophagus, linking the supra- and sub-oesophageal ganglia; together these three elements form a nerve ring that encircles the gut.
• The paired ventral nerve cord with its thoracic and abdominal ganglia runs along the ventral side and does not form the nerve ring; it serves segmental motor and sensory functions.
• Hence, the configuration described in Option C correctly identifies the structures that form the nerve ring; the other options are incomplete or refer to different parts of the nervous system.