301. Lateral ostia in the chambers of the cockroach heart are prevented from opening, while the muscular wall continues contracting rhythmically. The most direct consequence is:
ⓐ. immediate increase in haemolymph entry into every chamber
ⓑ. reduced filling of heart chambers from surrounding haemolymph
ⓒ. conversion of the dorsal heart into a ventral nerve cord
ⓓ. uninterrupted normal flow since ostia have no circulatory role
Correct Answer: reduced filling of heart chambers from surrounding haemolymph
Explanation: Lateral ostia are openings through which haemolymph enters the chambers of the dorsal heart from surrounding sinuses. If they remain closed, chamber filling is reduced even though the muscular wall can still contract. A pump that contracts without receiving an adequate volume of fluid cannot maintain normal output. The treatment does not change the tissue identity or position of the heart, and the ostia are not functionless perforations. Their role is directional entry of haemolymph into the chambered tube. The condition separates muscular contraction from filling: both are necessary for effective pumping. The muscular wall continues contracting rhythmically; this unaffected baseline separates the primary defect from a general collapse of the organ or tissue. Rhythmic activity alone cannot preserve normal anterior flow when the inlet pathway has been selectively disabled.
302. A tracer is placed in haemolymph near the posterior abdomen. With normal heart activity, its concentration first rises in successive heart chambers and then appears toward the anterior end. When heart contractions are stopped, anterior appearance is greatly delayed. The result indicates that the dorsal heart:
ⓐ. pumps haemolymph mainly toward the posterior end
ⓑ. performs gaseous exchange directly with tissues
ⓒ. produces haemocytes within each chamber
ⓓ. promotes anterior movement of haemolymph
Correct Answer: promotes anterior movement of haemolymph
Explanation: The tracer begins in posterior haemolymph and subsequently appears in the heart chambers before reaching the anterior region. This pattern shows movement from posterior toward anterior through the dorsal contractile tube. Stopping heart contractions greatly delays the anterior appearance, linking the directional transport to pumping activity rather than to passive distribution alone. The experiment does not measure gas exchange or production of haemocytes. It also contradicts posterior pumping, since the recorded tracer movement proceeds in the opposite direction. The inference remains appropriately limited: heart contraction is an important driver of anterior haemolymph flow within the open circulatory system. With normal heart activity, its concentration first rises in successive heart chambers and then appears toward the anterior end; this retained condition separates the specific lesion from general tissue death or complete organ failure. Distribution through haemocoelic sinuses can follow after the fluid leaves the main dorsal pathway.
303. Read the arrangement described below. Structure P is an elongated muscular tube lying dorsally through the thorax and abdomen. It is divided into funnel-shaped chambers, each receiving haemolymph through lateral openings. Structure P is:
ⓐ. the tracheal trunk carrying air from spiracles
ⓑ. the dorsal heart pumping haemolymph anteriorly
ⓒ. the alimentary canal moving food posteriorly
ⓓ. the ventral nerve cord coordinating segmental responses
Correct Answer: the dorsal heart pumping haemolymph anteriorly
Explanation: The combined clues identify the cockroach heart. It is an elongated muscular tube positioned dorsally and extending through thoracic and abdominal regions. Division into funnel-shaped chambers and the presence of lateral ostia distinguish it from other longitudinal structures. Haemolymph enters through these openings, and muscular contraction drives it toward the anterior end. Tracheal trunks contain air and connect with spiracles rather than receiving haemolymph through ostia. The alimentary canal carries food and has specialised digestive regions, while the nerve cord lies ventrally and bears ganglia. Position, chambering, inlet structure, fluid content, and direction of pumping together identify P as the dorsal heart. Its dorsal position and anterior pumping direction are consistent with the open circulatory organisation of the insect.
304. Associate each respiratory structure of a cockroach with its principal relation. Each Column II entry is used once.
| Column I | Column II |
|---|
| P. Spiracle | W. Fine terminal branch where diffusion occurs near tissues |
| Q. Trachea | X. Lateral external opening regulated by a sphincter |
| R. Tracheole | Y. Air-conducting tube that branches repeatedly |
| S. Spiracular sphincter | Z. Muscular control of opening and closing |
ⓐ. P-X, Q-Y, R-W, S-Z
ⓑ. P-Y, Q-X, R-Z, S-W
ⓒ. P-W, Q-Z, R-X, S-Y
ⓓ. P-Z, Q-W, R-Y, S-X
Correct Answer: P-X, Q-Y, R-W, S-Z
Explanation: A spiracle is a lateral external opening through which air enters or leaves the tracheal system, so P matches X. Each spiracle leads into tracheae, which form branching air-conducting tubes, giving Q with Y. Tracheoles are the finest terminal branches and lie close to tissues where respiratory gases diffuse, so R matches W. A sphincter is a muscular control associated with a spiracle and regulates whether the opening is open or closed, fixing S with Z. The mapping follows the pathway from the body surface to the cellular exchange region. It also separates a structural opening from the muscle that regulates it and distinguishes larger conducting tubes from fine diffusion branches.
305. Assess the following statements about cockroach respiration.
I. Ten pairs of spiracles occur along the lateral sides of the body.
II. Spiracles open into tracheae that branch into finer tracheoles.
III. Gas exchange occurs mainly between haemolymph and tissues through capillaries.
IV. Tracheoles deliver air close to cells, where diffusion occurs.
ⓐ. I and III only
ⓑ. II and III only
ⓒ. I, II and III only
ⓓ. I, II and IV only
Correct Answer: I, II and IV only
Explanation: The cockroach has ten pairs of lateral spiracles, making statement I valid. These openings connect with a system of tracheae that repeatedly branch into fine tracheoles, supporting statement II. Tracheoles approach tissues closely, and gases diffuse between their air and nearby cells, so statement IV is valid. Statement III incorrectly makes haemolymph and capillaries the main respiratory transport pathway. Cockroach haemolymph is not the principal carrier that delivers oxygen to tissues. The tracheal system provides a more direct route from the external openings to cellular regions. The valid combination preserves spiracle number, branching order, and the distinctive direct-delivery mechanism of insect respiration. Because tracheoles approach the tissues directly, haemolymph is not the principal carrier of respiratory gases in this system.
306. Every spiracular sphincter of a cockroach becomes unable to relax, while the tracheae and tracheoles remain structurally open. The earliest expected problem is:
ⓐ. reduced movement of food from the oesophagus into the crop
ⓑ. less airflow between the environment and tracheal system
ⓒ. conversion of haemolymph into an oxygen-carrying fluid
ⓓ. increased uric acid discharge through the hindgut
Correct Answer: less airflow between the environment and tracheal system
Explanation: Spiracular sphincters regulate the external openings of the tracheal system. If they cannot relax, the spiracles remain closed or severely narrowed, preventing normal movement of air between the environment and internal tracheae. The deeper tubes may remain structurally intact, but they cannot receive an adequate fresh-air supply through blocked entrances. Digestive storage, haemolymph composition, and uric-acid removal belong to other systems and are not the earliest direct consequences. The condition demonstrates that an intact branching network is insufficient when access at the body surface is lost. The tracheae and tracheoles remain structurally open; preserving this condition confines the immediate inference to the selectively altered feature. Respiratory function depends on both open conducting tubes and controlled communication with the external atmosphere.
307. Sequence the pathway followed by oxygen from the environment to a cockroach body cell.
P. Oxygen enters a fine tracheole.
Q. Oxygen passes through a lateral spiracle.
R. Oxygen diffuses from the tracheole to the nearby cell.
S. Oxygen travels through a larger tracheal tube.
ⓐ. \(S \rightarrow Q \rightarrow P \rightarrow R\)
ⓑ. \(Q \rightarrow P \rightarrow S \rightarrow R\)
ⓒ. \(Q \rightarrow S \rightarrow P \rightarrow R\)
ⓓ. \(P \rightarrow Q \rightarrow R \rightarrow S\)
Correct Answer: \(Q \rightarrow S \rightarrow P \rightarrow R\)
Explanation: Oxygen first crosses the body boundary through an open spiracle. It then enters the larger tracheal tubes, which conduct air inward and branch repeatedly. The pathway narrows into fine tracheoles that extend close to metabolically active cells. Oxygen finally diffuses from the tracheolar air across the short terminal distance into the neighbouring tissue. The sequence is spiracle, trachea, tracheole, and cell. It reflects decreasing tube diameter and increasing proximity to the exchange site. Haemolymph is not inserted as an obligatory intermediate, since the tracheal system delivers respiratory gases directly toward tissues. The start condition is that oxygen passes through a lateral spiracle, while the endpoint is that oxygen diffuses from the tracheole to the nearby cell; the middle events connect the initial trigger with the final biological consequence. Reversing the order would place internal branches before the external entry point or diffusion before oxygen reaches the terminal tube.
308. Equal cockroaches are kept at the same temperature and atmospheric oxygen level. In Group P, eight pairs of spiracles are sealed, while Group Q retains all ten pairs. P shows a major decline in oxygen uptake despite normal heart activity. The strongest inference is:
ⓐ. the dorsal heart is the only route by which oxygen reaches tissues
ⓑ. haemolymph fully replaces the blocked tracheal pathway
ⓒ. Malpighian tubules normally draw oxygen through the hindgut
ⓓ. functional spiracular openings are required for normal air entry
Correct Answer: functional spiracular openings are required for normal air entry
Explanation: Temperature and external oxygen concentration are controlled, and the heart remains active in both groups. The principal experimental change is sealing most spiracular openings. The accompanying decline in oxygen uptake links the loss of respiratory entry points with reduced access of air to the tracheal network. Normal cardiac activity cannot compensate since cockroach oxygen delivery depends mainly on tracheae and tracheoles rather than transport by haemolymph. Malpighian tubules have an excretory function and do not draw atmospheric oxygen through the hindgut. The result supports a specific requirement for functional spiracles at the first stage of the tracheal pathway. It does not imply that every single spiracle contributes equally under all conditions, only that extensive closure severely restricts normal air exchange.
309. A cockroach eliminates most nitrogenous waste in the form of uric acid. It is therefore described as:
ⓐ. ammonotelic
ⓑ. uricotelic
ⓒ. ureotelic
ⓓ. aminotelic
Correct Answer: uricotelic
Explanation: The term uricotelic applies to animals whose principal nitrogenous waste is uric acid. In a cockroach, Malpighian tubules remove nitrogenous wastes from haemolymph, process them into uric acid, and discharge the material into the hindgut. The waste then leaves with the contents of the alimentary canal. Ammonotelic animals eliminate nitrogen mainly as ammonia, while ureotelic animals rely mainly on urea. The classification is based on the chemical form of the major nitrogenous end product rather than on the location of the excretory organ. Applying the label requires the stated functional or developmental criterion, not merely the organism's habitat. Identifying the cockroach as uricotelic links Malpighian-tubule function with the type of waste finally expelled through the hindgut.
310. Relate each excretory component with its most appropriate relation. Each Column II entry is used once.
| Column I | Column II |
|---|
| P. Malpighian tubules | W. Receives excretory material before final elimination |
| Q. Haemolymph | X. Main tubules removing nitrogenous waste |
| R. Hindgut | Y. Fluid from which wastes are absorbed |
| S. Fat body, nephrocytes, and uricose glands | Z. Additional structures assisting excretion |
ⓐ. P-X, Q-Y, R-W, S-Z
ⓑ. P-Y, Q-X, R-Z, S-W
ⓒ. P-W, Q-Z, R-X, S-Y
ⓓ. P-Z, Q-W, R-Y, S-X
Correct Answer: P-X, Q-Y, R-W, S-Z
Explanation: Malpighian tubules are the principal excretory tubules and remove nitrogenous wastes from haemolymph, so P matches X. Haemolymph is the circulating fluid from which these wastes are taken, giving Q with Y. The tubules discharge their processed material into the hindgut, which receives it before elimination, so R matches W. Fat body, nephrocytes, and uricose glands provide additional assistance in excretory handling, linking S with Z. The mapping follows the source-pathway-destination relation while recognising supplementary structures. It avoids assigning the same role to every component: haemolymph carries the waste, tubules process and transfer it, the hindgut receives it, and accessory tissues contribute additional excretory support. The main tubules and accessory excretory tissues cooperate, but they retain different structures and immediate roles.
311. The glandular and ciliated cells of the Malpighian tubules are severely damaged, but the hindgut remains open and muscular movement of the gut continues. The most direct consequence is:
ⓐ. increased movement of food from the crop into the gizzard
ⓑ. normal waste removal through the open hindgut alone
ⓒ. less waste passes from haemolymph into Malpighian tubules
ⓓ. spiracle closure blocks entry into the excretory pathway
Correct Answer: less waste passes from haemolymph into Malpighian tubules
Explanation: Malpighian-tubule cells absorb nitrogenous wastes from the haemolymph and participate in their processing and movement toward the hindgut. Damage to these glandular and ciliated cells weakens the initial removal and tubular transport stages. An open and moving hindgut can eliminate material that reaches it, but it cannot replace the missing transfer from haemolymph into the tubules. The gizzard and spiracles belong to digestive and respiratory functions and are not directly altered by the specified injury. The condition separates outlet availability from excretory collection. The hindgut remains open and muscular movement of the gut continues; this retained condition anchors the comparison, so the observed consequence can be traced to the selected disruption. Normal elimination requires both a functioning receiving pathway in the hindgut and intact Malpighian tubules capable of supplying waste to that pathway.
312. Examine the statements below about cockroach excretion.
I. Malpighian tubules arise near the midgut-hindgut junction.
II. Their cells absorb nitrogenous wastes from haemolymph.
III. Excretory material is discharged into the hindgut.
IV. Fat body, nephrocytes, and uricose glands may also assist excretion.
ⓐ. I and III only
ⓑ. I, II, III and IV
ⓒ. II and IV only
ⓓ. I, II and IV only
Correct Answer: I, II, III and IV
Explanation: Malpighian tubules arise near the junction between the midgut and hindgut, making statement I valid. Their glandular and ciliated cells remove nitrogenous wastes from the haemolymph, supporting statement II. The processed material is conveyed into the hindgut and ultimately leaves through the alimentary outlet, so statement III is also valid. Excretion is not restricted entirely to the tubules; fat body, nephrocytes, and uricose glands provide supplementary assistance, making statement IV accurate. All four statements describe connected parts of the cockroach excretory organisation: location, source fluid, discharge route, and accessory participation. No statement introduces a conflicting organ or reverses the direction of waste movement. The tubules remove nitrogenous material from haemolymph and deliver it to the hindgut for elimination with minimal water loss.
313. A labelled nitrogenous compound is introduced into the haemolymph of two groups of cockroaches. In controls, the label later appears in Malpighian tubules and then in the hindgut. In treated animals, tubular uptake is blocked, and little label reaches the hindgut despite normal gut movement. The strongest conclusion is:
ⓐ. the hindgut removes most nitrogenous waste directly from atmospheric air
ⓑ. gut movement alone transfers waste from haemolymph into the lumen
ⓒ. Malpighian tubules secrete digestive juice into the foregut
ⓓ. Malpighian-tubule uptake links haemolymph waste with hindgut elimination
Correct Answer: Malpighian-tubule uptake links haemolymph waste with hindgut elimination
Explanation: In the control, the labelled compound follows a clear route from haemolymph into Malpighian tubules and then into the hindgut. Blocking tubular uptake interrupts that transfer even though the hindgut continues moving normally. The difference shows that gut motility cannot by itself collect nitrogenous waste from the circulating fluid. Malpighian tubules provide the essential link by absorbing waste from haemolymph and delivering processed material to the hindgut. Hepatic caeca, not Malpighian tubules, supply digestive secretion near the foregut-midgut junction. Normal gut movement persists in the treated animals, so the failure of labelled waste to reach the hindgut is traced specifically to blocked Malpighian-tubule uptake rather than loss of hindgut motility. The experiment supports a directional excretory pathway: haemolymph serves as the waste source, Malpighian tubules perform uptake and transfer, and the hindgut receives the material for final elimination.
314. Paired longitudinal connectives between a thoracic ganglion and the next ganglion are severed in a cockroach. The ganglia on both sides of the cut remain locally active. The most direct effect is:
ⓐ. the nervous system shifts from the ventral to the dorsal side
ⓑ. communication between the separated ganglionic regions is impaired
ⓒ. all compound-eye ommatidia are converted into antennae
ⓓ. Malpighian tubules stop removing nitrogenous wastes
Correct Answer: communication between the separated ganglionic regions is impaired
Explanation: The cockroach ventral nerve cord consists of segmental ganglia linked by paired longitudinal connectives. Ganglia can coordinate local activity, but signals must pass through the connectives to integrate responses across separated regions. Severing the link therefore disrupts communication across the cut even when ganglia on both sides remain capable of local processing. The lesion does not relocate the cord, alter the identity of sensory organs, or directly damage the excretory system. The changed condition distinguishes a local centre from the pathway joining centres. Preserved ganglia explain why some regional responses may remain, while loss of the connecting route explains poorer coordination between thoracic and more posterior segments. This is a network consequence rather than a simple reduction in the number of ganglia. Preserved ganglia on both sides of the cut show that the failure lies in transmission between centres rather than in their absence.
315. Link each nervous-system component of a cockroach with its most appropriate relation. Each Column II entry is used once.
| Column I | Column II |
|---|
| P. Supra-oesophageal ganglion | W. Six segmental centres in the abdomen |
| Q. Thoracic ganglia | X. Anterior centre supplying antennae and compound eyes |
| R. Abdominal ganglia | Y. Paired pathways linking successive ganglia |
| S. Longitudinal connectives | Z. Three centres associated with the thoracic region |
ⓐ. P-Y, Q-W, R-X, S-Z
ⓑ. P-Z, Q-X, R-Y, S-W
ⓒ. P-W, Q-Y, R-Z, S-X
ⓓ. P-X, Q-Z, R-W, S-Y
Correct Answer: P-X, Q-Z, R-W, S-Y
Explanation: The supra-oesophageal ganglion lies in the anterior head region and supplies sensory structures such as the antennae and compound eyes, so P matches X. The thorax contains three ganglia, linking Q with Z. Six ganglia occur in the abdomen, giving R with W. Paired longitudinal connectives run between successive ganglia and maintain communication along the ventral nervous pathway, so S matches Y. These structures form an integrated network rather than isolated neural masses. The anterior ganglion handles important head-related input, while thoracic and abdominal ganglia distribute control through the body. The connectives provide continuity between those centres, allowing local and whole-body responses to be coordinated. The nervous arrangement combines anterior sensory integration with repeated connections among segmental ganglia.
316. A cockroach retains all three thoracic and six abdominal ganglia, but several connections among the abdominal ganglia fail. Which conclusion is most accurate?
ⓐ. Ganglion number alone guarantees normal coordination
ⓑ. The abdominal ganglia become part of the dorsal circulatory vessel
ⓒ. Local ganglia may remain present while coordinated transmission across damaged connections declines
ⓓ. Every thoracic ganglion must also become non-functional
Correct Answer: Local ganglia may remain present while coordinated transmission across damaged connections declines
Explanation: Segmental ganglia and the connectives joining them perform different parts of nervous organisation. The stated cockroach still has the normal complement of thoracic and abdominal ganglia, so a count of ganglia would appear unchanged. Damage to the links between abdominal centres can nevertheless impair passage of signals and coordination across those regions. The ganglia do not become circulatory structures, and failure of some abdominal connections does not automatically destroy all thoracic centres. This distinction shows why anatomical presence is not identical to functional integration. A nervous system depends on both local processing units and continuous routes between them. The strongest inference therefore concerns reduced coordinated transmission despite preserved ganglion number, avoiding decorative subtraction that would not represent the actual defect described. The count therefore describes retained centres, whereas coordinated behaviour depends on their functional continuity.
317. The supra-oesophageal ganglion of a cockroach is selectively damaged, while the thoracic and abdominal ganglia remain functional. Which effect is most directly expected?
ⓐ. Immediate disappearance of all six walking legs
ⓑ. Complete loss of every local abdominal response
ⓒ. Impaired processing of antenna and compound-eye inputs
ⓓ. Conversion of the ventral nerve cord into a dorsal vessel
Correct Answer: Impaired processing of antenna and compound-eye inputs
Explanation: The supra-oesophageal ganglion is the major anterior neural centre associated with the antennae and compound eyes. Selective damage to it would most directly disrupt processing and coordination of sensory information arriving from these structures. Thoracic and abdominal ganglia are stated to remain functional, so some local control of legs, wings, abdominal muscles, and regional responses may persist. The walking legs do not disappear anatomically, and every abdominal response need not cease immediately. The nervous system also cannot transform into a circulatory structure. The case separates central anterior sensory integration from distributed segmental control. The thoracic and abdominal ganglia remain functional; this retained condition removes general deterioration as the main cause and identifies the disrupted relation. Damage to the brain region can impair orientation and sensory-guided behaviour even while posterior ganglia retain limited local activity.
318. Interpret the internal arrangement described below. Structure P lies below the alimentary canal and contains repeated ganglionic enlargements. Structure Q lies above the oesophagus in the head and sends nerves to the antennae and compound eyes. P and Q are, respectively:
ⓐ. dorsal heart vessel and sub-oesophageal ganglion
ⓑ. ventral nerve cord and supra-oesophageal ganglion
ⓒ. ventral alimentary canal and supra-oesophageal ganglion
ⓓ. ventral tracheal trunk and sub-oesophageal ganglion
Correct Answer: ventral nerve cord and supra-oesophageal ganglion
Explanation: A longitudinal structure lying below the alimentary canal and bearing repeated ganglia is the ventral nerve cord, identifying P. Structure Q lies above the oesophagus and supplies the antennae and compound eyes, which identifies it as the supra-oesophageal ganglion. These two regions are connected within the cockroach ganglionic nervous system but occupy different positions. The dorsal heart lies above the alimentary canal and carries haemolymph rather than neural impulses. A tracheal trunk conducts air and does not contain segmental ganglia. The spatial relation of ventral cord, dorsal anterior brain, and sensory nerves provides enough evidence to identify both structures without relying on an unseen diagram. The arrangement links repeated ventral ganglia with the anterior brain through circumpharyngeal connections around the oesophagus.
319. Antennae, maxillary and labial palps, compound eyes, and anal cerci occur in different body regions of a cockroach. Their shared relationship is that they:
ⓐ. contribute to sensory reception
ⓑ. form the complete alimentary canal
ⓒ. constitute the three pairs of walking legs
ⓓ. secrete the oothecal covering
Correct Answer: contribute to sensory reception
Explanation: The listed structures differ greatly in position and form, yet each participates in receiving information from the environment. Antennae and compound eyes are prominent head sense organs; maxillary and labial palps are associated with mouthparts and also provide sensory input; anal cerci occur at the posterior end and detect environmental changes. Their common category is therefore sensory rather than digestive, locomotory, or reproductive. The question does not imply that all detect the same stimulus with equal sensitivity. Instead, it asks for the higher-level relationship that unites them despite regional separation. Recognising that distribution across the head, mouthparts, and abdomen can still support one coordinated sensory system is more informative than matching each structure to an isolated label.
320. Each compound eye of a cockroach contains about \(2000\) ommatidia. A treatment makes \(25\%\) of the ommatidia in one eye and \(10\%\) in the other eye non-functional, without altering the remaining units. Approximately how many functional ommatidia remain in both eyes together?
ⓐ. \(3000\)
ⓑ. \(3200\)
ⓒ. \(3300\)
ⓓ. \(3500\)
Correct Answer: \(3300\)
Explanation: One eye retains \(75\%\) of its ommatidia after a \(25\%\) loss:
\[
2000 \times \frac{75}{100}=1500. \]
The other eye retains \(90\%\) after a \(10\%\) loss:
\[
2000 \times \frac{90}{100}=1800. \]
The combined number of functional ommatidia is
\[
1500+1800=3300. \]
The two percentages cannot be averaged and applied once unless the equal starting numbers are first recognised; calculating each eye separately makes the biological grouping explicit. Ommatidia are the repeated visual units of the compound eyes, and their combined inputs contribute to mosaic vision. The result is approximate: the starting count of \(2000\) per eye is itself approximate, and it reports functioning units rather than visual resolution directly. The loss is unequal between the eyes, so calculating one common percentage would hide the two treatment conditions. Summing the surviving units after separate percentage conversions preserves both the bilateral organisation and the stated asymmetry.
