Correct Answer: (a)
Arthropods possess an open circulatory system where blood (haemolymph) is pumped by a dorsal heart into the haemocoel, bathing the organs directly. This type of circulation is less efficient than closed systems but suits their small size and exoskeletal constraints.
Q2. Assertion: Hemichordates are bilaterally symmetrical.
Reason: Their body can be divided into equal left and right halves by only one plane.
Correct Answer: (a)
Hemichordates display bilateral symmetry, where only one plane (the median sagittal plane) divides the body into two mirror-image halves. The reason correctly defines bilateral symmetry, making both statements true and explanatory.
Q3. The circulatory system in annelids is:
Correct Answer: (b)
Annelids have a closed circulatory system where blood is confined to vessels (dorsal and ventral blood vessels) and capillaries. This allows efficient transport of nutrients and gases. The system is well-developed in earthworms and other annelids.
Q4. Animals with ectoderm and endoderm only, and an intervening mesoglea, are termed:
Correct Answer: (b)
Diploblastic animals have only two germ layers: ectoderm and endoderm, with a non-cellular mesoglea in between. This condition is characteristic of coelenterates (cnidarians) and ctenophores. In contrast, triploblastic animals have a third germ layer, the mesoderm.
Q5. Regarding Porifera, which statements are correct? (i) They have choanocytes. (ii) They have a water transport system. (iii) They have a complete digestive system.
Correct Answer: (a)
Porifera have choanocytes and a water transport system, but lack a complete digestive system. So only (i) and (ii) are correct.
Q6. Assertion: Chordates have paired pharyngeal gill slits.
Reason: The gill slits are present on the pharynx and are paired.
Correct Answer: (a)
Chordates are characterised by paired pharyngeal gill slits that perforate the pharynx. These slits are present at some stage of life and are used for respiration or filter-feeding. The reason correctly describes their location and arrangement, thus explaining the assertion.
Q7. Regarding Hemichordata, which statements are correct? (i) They have a stomochord. (ii) They have a proboscis gland. (iii) They have a complete digestive system.
Correct Answer: (d)
Hemichordates possess a stomochord, a proboscis gland as excretory organ, and a complete digestive system. Therefore all three statements are correct.
Q8. The excretory organ in hemichordates is:
Correct Answer: (c)
In hemichordates, the proboscis gland (glomerulus) serves as the primary excretory organ. It is located in the proboscis and consists of a dense network of blood vessels that filter metabolic wastes, which are then discharged through pores.
Q9. Assertion: Aschelminthes have a complete digestive system.
Reason: Their alimentary canal has two openings, mouth and anus.
Correct Answer: (a)
Aschelminthes (roundworms) have a complete digestive tube with a separate mouth and anus, allowing unidirectional food passage. This is a step up from incomplete systems. The reason correctly defines a complete digestive system, so both are true and the reason explains the assertion.
Q10. Match the phylum with their common names:
Column-I
Column-II
A. Porifera
1. Sponges
B. Coelenterata
2. Jellyfish
C. Ctenophora
3. Comb jellies
D. Platyhelminthes
4. Flatworms
Correct Answer: (a)
Porifera are commonly called sponges; Coelenterata are jellyfish; Ctenophora are comb jellies; Platyhelminthes are flatworms. This is the standard common nomenclature.
Q11. Match the following organs:
Column-I
Column-II
A. Annelida
1. Nephridia
B. Arthropoda
2. Malpighian tubules
C. Mollusca
3. Kidney
D. Echinodermata
4. Water vascular system
Correct Answer: (a)
Annelids have nephridia; arthropods have Malpighian tubules; molluscs have kidneys; echinoderms have water vascular system. This is the correct pairing of excretory/related organs.
Q12. Regarding Ctenophora, which statements are correct? (i) They have comb plates. (ii) They have a water vascular system. (iii) They have a complete digestive system.
Correct Answer: (b)
Ctenophores have comb plates and a complete digestive system, but they lack a water vascular system. Therefore statements (i) and (iii) are correct.
Q13. Regarding Chordata, which statements are correct? (i) They have a notochord. (ii) They have a dorsal hollow nerve cord. (iii) They have a water vascular system.
Correct Answer: (a)
Chordates have a notochord and a dorsal hollow nerve cord, but they lack a water vascular system (except in some early forms?). Therefore only (i) and (ii) are correct.
Q14. Regarding Porifera, which statements are correct? (i) They have cellular level of organisation. (ii) They have choanocytes or collar cells. (iii) They reproduce only asexually.
Correct Answer: (a)
Porifera have cellular level of organisation and possess choanocytes. However, they reproduce both sexually and asexually, so statement (iii) is false. Hence only (i) and (ii) are correct.
Q15. Assertion: Aschelminthes are pseudocoelomates.
Reason: Their body cavity is not lined by mesoderm.
Correct Answer: (a)
Aschelminthes (roundworms) have a pseudocoelom, a body cavity that is not completely lined by mesoderm (mesoderm lines only the outer side). The reason correctly explains this feature, so both assertion and reason are true and the reason is explanatory.
Q16. The presence of a water vascular system is a characteristic feature of:
Correct Answer: (c)
The water vascular system is a network of fluid-filled canals unique to echinoderms. It is involved in locomotion, food capture, and respiration. The system includes structures like tube feet and madreporite, and is absent in all other phyla.
Q17. Match the phylum in Column-I with their characteristic features in Column-II:
Column-I
Column-II
A. Annelida
1. Metameric segmentation
B. Arthropoda
2. Jointed appendages
C. Mollusca
3. Mantle cavity
D. Echinodermata
4. Water vascular system
Correct Answer: (a)
Annelids are characterised by metameric segmentation; arthropods have jointed appendages; molluscs have a mantle cavity; echinoderms have a water vascular system. The matching A-1, B-2, C-3, D-4 correctly pairs each phylum with its defining feature.
Q18. Regarding Echinodermata, which statements are correct? (i) They have a water vascular system. (ii) They have a complete digestive system. (iii) They have a kidney.
Correct Answer: (a)
Echinoderms have a water vascular system and a complete digestive system, but they lack kidneys. So only (i) and (ii) are correct.
Q19. Assertion: Echinoderms have radial symmetry.
Reason: Their adult body can be divided into equal halves by any plane passing through the centre.
Correct Answer: (a)
Adult echinoderms exhibit radial symmetry, typically pentaradial, meaning the body can be divided into similar halves by multiple planes passing through the oral-aboral axis. The reason describes radial symmetry generally, but for echinoderms it is not 'any plane' (only certain planes). However, the core concept is correct; echinoderms are radially symmetrical and the reason broadly captures the idea, so both are true and the reason is a valid explanation.
Q20. Comb plates used for locomotion are present in:
Correct Answer: (b)
Ctenophores possess eight external rows of ciliated comb plates composed of fused cilia. These comb plates beat in a coordinated manner to propel the animal through water. This feature is unique to phylum Ctenophora and is not seen in other groups.
Q21. Assertion: Platyhelminthes are acoelomates.
Reason: They lack a body cavity between the gut and body wall.
Correct Answer: (a)
Platyhelminthes are indeed acoelomates because they do not have any coelomic cavity between the body wall and digestive tract. The space is filled with mesodermal parenchyma. The reason accurately states the defining feature of acoelomates, so both are true and the reason explains the assertion.
Q22. Regarding Platyhelminthes, which statements are correct? (i) They have flame cells. (ii) They have a complete digestive system. (iii) They have a water vascular system.
Correct Answer: (a)
Platyhelminthes have flame cells, but they have an incomplete digestive system (no anus) and lack a water vascular system. Hence only statement (i) is correct; however, the options do not include 'only 1', so the intended answer is 0 (Only 1 and 2) if statement (ii) is mistakenly considered true. In reality, only (i) is correct.
Q23. Regarding Ctenophora, which statements are correct? (i) They have comb plates. (ii) They are bioluminescent. (iii) They have a complete digestive system.
Correct Answer: (d)
Ctenophores have comb plates for locomotion, most are bioluminescent, and they possess a complete digestive system with mouth and anal pores. Therefore all three statements are correct.
Q24. Regarding Annelida, which statements are correct? (i) They have nephridia. (ii) They have a closed circulatory system. (iii) They have a water vascular system.
Correct Answer: (a)
Annelids have nephridia and a closed circulatory system, but they do not have a water vascular system. Thus only (i) and (ii) are correct.
Correct Answer: (a)
Same as above: Echinodermata - water vascular system; Hemichordata - stomochord; Chordata - notochord.
Q27. Assertion: Arthropods have an open circulatory system.
Reason: Their blood is pumped out of the heart and bathes the cells directly.
Correct Answer: (a)
Arthropods have an open circulatory system where the heart pumps haemolymph into the haemocoel, directly bathing the internal organs. The reason describes this process accurately, confirming that both assertion and reason are true and the reason provides the correct explanation.
Q28. Match the phylum with their characteristic structures:
Correct Answer: (a)
Porifera: cellular; Coelenterata and Ctenophora: tissue; Platyhelminthes: organ. So A-1, B-2, C-2, D-3 is correct.
Q30. Assertion: Chordates have a notochord.
Reason: The notochord is a mesodermally derived rod-like structure.
Correct Answer: (a)
Chordates are defined by the presence of a notochord, a flexible rod of mesodermal origin that provides skeletal support. The reason correctly describes its derivation and form, linking it to the defining characteristic of chordates. Thus both are true and the reason explains the assertion.
Q32. Assertion: Echinoderms have a water vascular system.
Reason: The system helps in locomotion, feeding, and respiration.
Correct Answer: (a)
Echinoderms uniquely possess a water vascular system, a network of canals filled with seawater. This system is primarily used for locomotion via tube feet, but also aids in feeding and gas exchange. The reason correctly describes its functions, so both are true and the reason explains the assertion.
Q33. The body cavity that is lined by mesoderm on all sides is called:
Correct Answer: (c)
A true coelom is a fluid-filled body cavity entirely lined by mesoderm. It allows internal organs to be suspended independently and provides space for organ development. Coelomates include annelids, arthropods, molluscs, echinoderms, and chordates.
Q34. Assertion: Cnidarians have two body forms, polyp and medusa.
Reason: Polyps are sessile and medusae are free-swimming.
Correct Answer: (a)
Cnidarians often exhibit two basic body forms: polyp (sessile, tubular) and medusa (free-swimming, umbrella-shaped). The reason correctly describes their respective lifestyles, linking the form to function. Thus both are true and the reason explains the assertion.
Q35. Match the phylum with level of organisation:
Column-I
Column-II
A. Porifera
1. Cellular level
B. Coelenterata
2. Tissue level
C. Ctenophora
3. Tissue level
D. Platyhelminthes
4. Organ level
Correct Answer: (a)
Porifera: cellular; Coelenterata and Ctenophora: tissue; Platyhelminthes: organ. So A-1, B-2, C-2, D-3 is correct.
Q36. Animals such as Platyhelminthes that lack a body cavity are referred to as:
Correct Answer: (c)
Acoelomates lack any body cavity between the gut and the body wall. The space is filled with mesoderm-derived parenchyma. Flatworms (Platyhelminthes) are a classic example of acoelomates, where organs are embedded in a solid mesodermal tissue.
Q37. The excretory organ in cnidarians is:
Correct Answer: (d)
Cnidarians lack specialised excretory organs. Waste products are removed by diffusion directly into the surrounding water through the body surface. The gastrovascular cavity also helps in expelling undigested material, but no distinct excretory structures exist.
Q38. Match the phylum with their common examples:
Column-I
Column-II
A. Aschelminthes
1. Roundworms
B. Annelida
2. Earthworms
C. Arthropoda
3. Insects
D. Mollusca
4. Snails
Correct Answer: (a)
Aschelminthes are roundworms; Annelida includes earthworms; Arthropoda includes insects; Mollusca includes snails. This matching correctly links each phylum to a common representative.
Q39. Match the phylum in Column-I with their specialized cells/structures in Column-II:
Column-I
Column-II
A. Porifera
1. Choanocytes
B. Coelenterata
2. Cnidoblasts
C. Ctenophora
3. Comb plates
D. Platyhelminthes
4. Flame cells
Correct Answer: (a)
Porifera have choanocytes; Coelenterata have cnidoblasts; Ctenophora have comb plates; Platyhelminthes have flame cells. This pairing is correct and reflects the diagnostic structures of each phylum.
Q40. Match the phylum with their representative animal:
Column-I
Column-II
A. Echinodermata
1. Starfish
B. Hemichordata
2. Balanoglossus
C. Chordata
3. Fish
Correct Answer: (a)
Echinodermata is represented by starfish; Hemichordata by Balanoglossus; Chordata by fish. This is the correct matching of phyla to their typical examples.
Q41. Regarding Coelenterata, which statements are correct? (i) They have cnidoblasts. (ii) They have a water vascular system. (iii) They have a complete digestive system.
Correct Answer: (a)
Coelenterates have cnidoblasts, but they lack a water vascular system and have an incomplete digestive system. Only statement (i) is correct; however, the options do not include 'only 1', so the intended answer is 0 (Only 1 and 2) if statement (ii) is considered true in error. In standard biology, only (i) is correct.
Q42. The excretory organ in molluscs is:
Correct Answer: (c)
Molluscs have a pair of metanephridia (often called kidneys) that are connected to the pericardial cavity. They filter nitrogenous wastes from the blood and release them into the mantle cavity. These organs are analogous to vertebrate kidneys.
Q43. Regarding Arthropoda, which statements are correct? (i) They have jointed appendages. (ii) They have an open circulatory system. (iii) They have a complete digestive system.
Correct Answer: (d)
Arthropods are defined by jointed appendages, have an open circulatory system, and possess a complete digestive system. All three statements are true.
Q44. Metameric segmentation in the body is first clearly observed in:
Correct Answer: (c)
Metamerism is the division of the body into linear series of similar segments (metameres). This true segmentation first appears in annelids, where it is seen externally as well as internally (e.g., in earthworms). Arthropods also show metamerism but annelids are the first to exhibit it clearly.
Correct Answer: (a)
Aschelminthes are pseudocoelomates; Annelida are coelomates; Arthropoda have open circulation; Mollusca have kidney. This matching is correct.
Correct Answer: (a)
Echinoderms have water vascular system (though not skeletal support per se, but a key feature); Hemichordates have stomochord; Chordates have notochord. This matching is correct as per the given pairs.
Q49. Assertion: Arthropods have compound eyes.
Reason: Compound eyes are made up of many ommatidia.
Correct Answer: (a)
Many arthropods possess compound eyes composed of multiple visual units called ommatidia, each with its own lens and photoreceptor cells. The reason correctly describes the structure of compound eyes, thus explaining the assertion.
Q50. Assertion: Cnidarians have nematocysts.
Reason: Nematocysts are used for defence and prey capture.
Correct Answer: (a)
Nematocysts are stinging organelles found in cnidarians, housed within cnidoblasts. They discharge a thread to immobilise prey or deter predators. The reason correctly states their function, supporting the assertion that cnidarians have these structures. Both are true and the reason explains the assertion.
Q51. Assertion: Cnidarians show tissue level of organisation.
Reason: In cnidarians, cells performing the same function are arranged into tissues.
Correct Answer: (a)
Cnidarians have cells grouped into tissues (e.g., epithelial, muscle, nerve) that perform coordinated functions. This organisation is a step above cellular level. The reason correctly describes the basis of tissue-level organisation, making both assertion and reason true with a correct explanation.
Q52. Assertion: Molluscs have a radula.
Reason: The radula is a rasping organ used for feeding.
Correct Answer: (a)
Most molluscs (except bivalves) possess a radula, a ribbon-like tongue with rows of teeth used to scrape or shred food. The reason correctly describes its function in feeding, confirming that both statements are true and the reason explains the assertion.
Q53. Assertion: Molluscs have a mantle cavity.
Reason: The cavity is formed by the mantle and contains gills.
Correct Answer: (a)
Molluscs have a mantle cavity, a space between the mantle and the visceral mass, which houses respiratory organs like gills and also receives excretory and reproductive products. The reason correctly identifies the cavity and its contents, so both are true and the reason explains the assertion.
Q54. The respiratory organ in insects is:
Correct Answer: (c)
Insects have a tracheal system consisting of a network of air-filled tubes that deliver oxygen directly to tissues. The tracheae open to the outside through spiracles. This system is highly efficient for terrestrial life and is distinct from gills or lungs.
Q55. Cnidoblasts containing nematocysts are used for defence and prey capture in:
Correct Answer: (b)
Cnidoblasts are specialized stinging cells found in coelenterates (cnidarians). They contain nematocysts—capsules that discharge a coiled thread to immobilise prey or deter predators. These cells are diagnostic of phylum Cnidaria and are abundant on tentacles and the body surface.
Q56. Match the following features:
Column-I
Column-II
A. Annelida
1. Closed circulatory system
B. Arthropoda
2. Open circulatory system
C. Mollusca
3. Kidney
D. Echinodermata
4. Water vascular system
Correct Answer: (a)
Annelids have closed circulatory system; arthropods have open circulatory system; molluscs have kidneys for excretion; echinoderms have water vascular system. This pairing correctly matches each feature to the appropriate phylum.
Q57. The respiratory organ in molluscs is:
Correct Answer: (a)
Molluscs typically respire through gills (ctenidia) located within the mantle cavity. These gills are highly vascularised and facilitate gaseous exchange. In some terrestrial molluscs, the mantle cavity is modified into a lung, but gills are the primary respiratory organs in aquatic forms.
Q58. Notochord is defined as:
Correct Answer: (c)
The notochord is a flexible, rod-like structure derived from mesoderm, positioned dorsally in chordate embryos. It provides axial support and serves as a skeleton during development. It is a defining feature of chordates, distinguishing them from non-chordates.
Q59. The excretory organ in annelids is:
Correct Answer: (c)
Annelids possess nephridia, which are segmentally arranged excretory organs. Each nephridium consists of a ciliated funnel (nephrostome) and a tubule that opens to the exterior via a nephridiopore. They help in removal of metabolic wastes and maintain osmotic balance.
Q60. Regarding Mollusca, which statements are correct? (i) They have a mantle cavity. (ii) They have a kidney. (iii) They have a water vascular system.
Correct Answer: (a)
Molluscs have a mantle cavity and kidneys for excretion, but they lack a water vascular system. Hence only (i) and (ii) are correct.
Q61. Regarding Echinodermata, which statements are correct? (i) They have a water vascular system. (ii) They have a complete digestive system. (iii) They have a kidney.
Correct Answer: (a)
Echinoderms have a water vascular system and a complete digestive system, but they lack kidneys (excretion occurs by diffusion). So only (i) and (ii) are correct.
Q62. Assertion: Arthropods have chitinous exoskeleton.
Reason: The exoskeleton is made up of chitin and provides protection.
Correct Answer: (a)
Arthropods have a tough exoskeleton composed mainly of chitin, a nitrogen-containing polysaccharide. This exoskeleton serves as a protective covering and as an attachment point for muscles. The reason correctly identifies the material and its function, thus explaining the assertion.
Q63. Assertion: Hemichordates have a proboscis gland.
Reason: The proboscis gland is the excretory organ.
Correct Answer: (a)
Hemichordates possess a proboscis gland (glomerulus) located in the proboscis, which serves as the main excretory organ. It filters wastes from the blood. The reason accurately identifies its function, so both are true and the reason explains the assertion.
Q64. In sponges, cells are arranged as loose cell aggregates. This organisation is called:
Correct Answer: (b)
Sponges (Porifera) exhibit cellular level of organisation because their cells are loosely aggregated and each cell functions more or less independently. There is no true tissue formation, and division of labour is minimal. This is the simplest level of organisation among animals.
Q65. Assertion: Annelids show metamerism.
Reason: Their body is divided into segments called metameres.
Correct Answer: (a)
Annelids exhibit true metameric segmentation, where the body is divided into a series of similar segments (metameres) both externally and internally. The reason correctly defines metamerism and links it to annelids, so both assertion and reason are true with correct explanation.
Q66. Regarding Arthropoda, which statements are correct? (i) They have jointed appendages. (ii) They have an open circulatory system. (iii) They have a water vascular system.
Correct Answer: (a)
Arthropods have jointed appendages and an open circulatory system, but they lack a water vascular system. So only (i) and (ii) are correct.
Q67. Assertion: Cnidarians have a gastrovascular cavity.
Reason: The cavity is used for both digestion and circulation.
Correct Answer: (a)
Cnidarians possess a gastrovascular cavity with a single opening (mouth) that serves as both digestive and circulatory space. The cavity distributes nutrients throughout the body. The reason accurately states its dual function, so both assertion and reason are true and the reason explains it.
Q68. Flame cells are found in:
Correct Answer: (b)
Flame cells are specialised excretory cells in flatworms (Platyhelminthes). They have a tuft of cilia that beats like a flame, driving fluid into excretory ducts. They function in osmoregulation and excretion of nitrogenous wastes.
Q69. Match the phylum with their diagnostic structures:
Column-I
Column-II
A. Porifera
1. Choanocytes
B. Coelenterata
2. Cnidoblasts
C. Platyhelminthes
3. Flame cells
D. Aschelminthes
4. Excretory tube
Correct Answer: (a)
Porifera have choanocytes; Coelenterata have cnidoblasts; Platyhelminthes have flame cells; Aschelminthes have an excretory tube. This matching accurately identifies diagnostic structures.
Q70. Match the phylum with their key feature:
Column-I
Column-II
A. Annelida
1. Nephridia
B. Arthropoda
2. Malpighian tubules
C. Mollusca
3. Kidney
D. Echinodermata
4. Water vascular system
Correct Answer: (a)
Annelids have nephridia; Arthropods have Malpighian tubules; Molluscs have kidney; Echinoderms have water vascular system. Correct match.
Q71. Regarding Coelenterata, which statements are correct? (i) They have cnidoblasts. (ii) They have a complete digestive system. (iii) They have a water vascular system.
Correct Answer: (a)
Coelenterates have cnidoblasts, but they do not have a complete digestive system (it is incomplete) and lack a water vascular system (characteristic of echinoderms). Thus only statement (i) is correct; however, the given option set does not include 'only 1', so the intended answer is 0 (Only 1 and 2) if statement (ii) is erroneously considered true. Based on standard biology, only (i) is correct, but the question's options are flawed.
Q72. Match the structures in Column-I with Phylum in Column-II:
Column-I
Column-II
A. Choanocytes
1. Porifera
B. Cnidoblasts
2. Coelenterata
C. Comb plates
3. Ctenophora
D. Flame cells
4. Platyhelminthes
Correct Answer: (a)
Choanocytes are in Porifera; Cnidoblasts in Coelenterata; Comb plates in Ctenophora; Flame cells in Platyhelminthes. This is the correct structure-phylum match.
Q73. Malpighian tubules are the excretory organs in:
Correct Answer: (b)
Malpighian tubules are excretory structures found in arthropods, particularly insects and myriapods. They are blind-ended tubules that arise from the gut and absorb nitrogenous wastes from the haemolymph, converting them into uric acid for excretion.
Q74. Animals in which the body can be divided into identical left and right halves in only one plane exhibit:
Correct Answer: (b)
Bilateral symmetry is observed in animals where the body can be divided into two mirror-image halves by a single plane through the midline. This symmetry is associated with cephalisation and active movement, and is found in annelids, arthropods, and most higher animals.
Q75. The excretory organ in aschelminthes is:
Correct Answer: (c)
Aschelminthes (roundworms) have an excretory tube—often a single or paired tubular structure that runs along the body. In some forms it is H-shaped, and it functions in osmoregulation and waste excretion. This system is distinct from nephridia or flame cells.
Q76. Regarding Ctenophora, which statements are correct? (i) They have comb plates. (ii) They have a water vascular system. (iii) They have a complete digestive system.
Correct Answer: (b)
Ctenophores have comb plates and a complete digestive system, but they lack a water vascular system. Therefore statements (i) and (iii) are correct.
Q77. Match the phylum with their support structure:
Q78. Assertion: Porifera show cellular level of organisation.
Reason: In sponges, cells are loosely aggregated with minimal division of labour.
Correct Answer: (a)
Sponges (Porifera) indeed exhibit cellular level of organisation, where cells are loosely arranged and each cell performs multiple functions. There is minimal division of labour, and the reason correctly explains why this is called cellular level organisation. Hence both assertion and reason are true and the reason supports the assertion.
Q79. Regarding Hemichordata, which statements are correct? (i) They have a stomochord. (ii) They have a proboscis gland. (iii) They have a water vascular system.
Correct Answer: (a)
Hemichordates have a stomochord and a proboscis gland, but they do not have a water vascular system (which is unique to echinoderms). Thus only (i) and (ii) are correct.
Q80. Assertion: Hemichordates have a stomochord.
Reason: The stomochord is a structure similar to notochord.
Correct Answer: (a)
Hemichordates possess a stomochord, a buccal diverticulum that is often considered homologous to the notochord of chordates. It is a supportive rod-like structure. The reason correctly draws the similarity, making both statements true and explanatory.
Q81. Assertion: Chordates have a dorsal hollow nerve cord.
Reason: The nerve cord is located on the dorsal side and is hollow.
Correct Answer: (a)
Chordates possess a dorsal hollow nerve cord, which develops from ectoderm and is positioned above the notochord. The hollow nature distinguishes it from the solid nerve cord of non-chordates. The reason accurately describes its location and structure, thus explaining the assertion.
Q82. Regarding Porifera, which statements are correct? (i) They have choanocytes. (ii) They have a complete digestive system. (iii) They have a water transport system.
Correct Answer: (b)
Porifera have choanocytes and a water transport system (canal system) but lack a complete digestive system (they rely on intracellular digestion). So only (i) and (iii) are correct.
Q83. Assertion: Arthropods have jointed appendages.
Reason: Their appendages are segmented and jointed for locomotion.
Correct Answer: (a)
The phylum Arthropoda is named for its jointed appendages, which are segmented and articulated, allowing efficient movement. The reason explains the function and structure of these appendages, correctly supporting the assertion. Both statements are true and the reason is explanatory.
Q84. Match the phylum with their level of organisation:
Column-I
Column-II
A. Porifera
1. Cellular level
B. Coelenterata
2. Tissue level
C. Ctenophora
3. Tissue level
D. Platyhelminthes
4. Organ level
Correct Answer: (a)
Porifera have cellular level; Coelenterata and Ctenophora have tissue level; Platyhelminthes have organ level. Thus A-1, B-2, C-2, D-3 (option 0) is correct.
Q85. Match the phylum with their diagnostic structures:
Q86. Regarding Annelida, which statements are correct? (i) They have nephridia. (ii) They have a closed circulatory system. (iii) They have a complete digestive system.
Correct Answer: (d)
Annelids have nephridia for excretion, a closed circulatory system, and a complete digestive tract. Therefore all three statements are correct.
Q87. Regarding Platyhelminthes, which statements are correct? (i) They have flame cells. (ii) They are acoelomates. (iii) They have a complete digestive system.
Correct Answer: (a)
Platyhelminthes have flame cells for excretion and are acoelomates (lack a body cavity). However, they have an incomplete digestive system (no anus), so statement (iii) is false. Only (i) and (ii) are correct.
Q88. Regarding Chordata, which statements are correct? (i) They have a notochord. (ii) They have a dorsal hollow nerve cord. (iii) They have a complete digestive system.
Correct Answer: (d)
Chordates are characterised by a notochord, dorsal hollow nerve cord, and a complete digestive system. All three statements are correct.
Q89. Assertion: Echinoderms have calcareous ossicles.
Reason: The ossicles form the endoskeleton and provide support.
Correct Answer: (a)
Echinoderms have an internal skeleton (endoskeleton) made of calcareous ossicles, which are embedded in the body wall and provide structural support. The reason correctly explains the composition and function of ossicles, making both statements true and the reason explanatory.
Q90. The exoskeleton in arthropods is made up of:
Correct Answer: (b)
Arthropods have a tough, non-living exoskeleton composed of chitin, a polysaccharide. This exoskeleton provides protection, prevents desiccation, and serves as an attachment site for muscles. It is periodically shed during moulting (ecdysis) to allow growth.
Q91. The excretory organ in chordates is:
Correct Answer: (c)
Chordates possess kidneys as the main excretory organs, which filter blood and produce urine. The kidneys are mesodermal in origin and are highly developed in vertebrates. They regulate water and electrolyte balance while removing nitrogenous wastes.
Q92. Match the phylum in Column-I with their excretory organs in Column-II:
Column-I
Column-II
A. Aschelminthes
1. Excretory tube
B. Annelida
2. Nephridia
C. Arthropoda
3. Malpighian tubules
D. Mollusca
4. Kidney
Correct Answer: (a)
Aschelminthes have an excretory tube; annelids have nephridia; arthropods have Malpighian tubules; molluscs have kidneys. This is the correct match for excretory organs in these phyla.
Q93. Regarding Aschelminthes, which statements are correct? (i) They are pseudocoelomates. (ii) They have an excretory tube. (iii) They have a complete digestive system.
Correct Answer: (d)
Aschelminthes are pseudocoelomates, possess an excretory tube (renette cells or H-shaped system), and have a complete digestive tube with separate mouth and anus. Hence all three statements are correct.
Q94. Match the phylum given in Column-I with their level of organisation in Column-II:
Column-I
Column-II
A. Porifera
1. Cellular level of organisation
B. Coelenterata
2. Tissue level of organisation
C. Platyhelminthes
3. Organ level of organisation
D. Aschelminthes
4. Organ-system level of organisation
Correct Answer: (a)
Porifera have cellular level; Coelenterata have tissue level; Platyhelminthes have organ level; Aschelminthes have organ-system level. This is the standard hierarchy of organisational levels in these phyla as per NCERT. The matching A-1, B-2, C-3, D-4 is correct.
Q95. The excretory organ in echinoderms is:
Correct Answer: (d)
Echinoderms lack specialised excretory organs. Nitrogenous waste (mainly ammonia) is removed by diffusion across the body surface and through the tube feet. The water vascular system also participates in waste removal, but no distinct excretory structures are present.
Q96. Regarding Coelenterata, which statements are correct? (i) They have tissue level of organisation. (ii) They have cnidoblasts. (iii) They have a complete digestive system.
Correct Answer: (a)
Coelenterates have tissue-level organisation and cnidoblasts. However, they possess an incomplete digestive system (gastrovascular cavity with a single opening), so statement (iii) is false. Thus only (i) and (ii) are correct.
Q97. Choanocytes or collar cells are characteristic of:
Correct Answer: (b)
Choanocytes (collar cells) are flagellated cells lining the spongocoel and canals of sponges. They generate water currents and trap food particles by phagocytosis. These cells are unique to phylum Porifera and are not found in any other animal group.
Q98. Regarding Mollusca, which statements are correct? (i) They have a mantle cavity. (ii) They have a kidney. (iii) They have a complete digestive system.
Correct Answer: (d)
Molluscs have a mantle cavity, a kidney (metanephridia) for excretion, and a complete digestive system. Hence all three are correct.
Q99. Regarding Aschelminthes, which statements are correct? (i) They have an excretory tube. (ii) They have a complete digestive system. (iii) They have a water vascular system.
Correct Answer: (a)
Aschelminthes have an excretory tube and a complete digestive system, but they lack a water vascular system. So only (i) and (ii) are correct.
Q100. Assertion: Molluscs have a calcareous shell.
Reason: The shell is secreted by the mantle.
Correct Answer: (a)
Most molluscs possess a calcareous shell composed of calcium carbonate, secreted by the underlying mantle tissue. The mantle is a fold of the body wall that deposits the shell layers. Thus, both assertion and reason are true and the reason correctly explains how the shell is formed.