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CHSE Odisha Elective Biology study materials
CHSE Odisha Elective Biology study resources

CHSE Odisha Elective Biology practice questions

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Question 1Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

In the five-kingdom classification proposed by R. H. Whittaker, which kingdom includes unicellular eukaryotes such as Euglena and Paramecium?

  1. Monera
  2. Fungi
  3. Protista Correct answer.
  4. Animalia

Explanation

Whittaker's five-kingdom system places all eukaryotic organisms that are predominantly unicellular, or that lack the tissue-level organisation of plants and animals, in Kingdom Protista. Euglena and Paramecium are classic protistan examples. Monera covers prokaryotes, Fungi covers heterotrophic absorptive eukaryotes, and Animalia covers multicellular heterotrophic consumers.

Question 2Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following features is characteristic of organisms placed in Kingdom Monera?

  1. Presence of chitinous cell walls and absorptive nutrition
  2. Absence of a membrane-bound nucleus and membrane-bound organelles Correct answer.
  3. Presence of cellulose cell walls and chloroplasts
  4. Presence of histone-bound DNA within a nuclear envelope

Explanation

Monera comprises prokaryotes, whose defining feature is the absence of a membrane-bound nucleus and other membrane-bound organelles. Their genetic material is a naked circular DNA molecule not enclosed by a nuclear envelope. Cell walls, when present, contain peptidoglycan rather than cellulose or chitin.

Question 3Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

The binomial name Mangifera indica was given by Linnaeus. In this name, the word 'indica' refers to which rank?

  1. Family
  2. Author citation
  3. Species epithet Correct answer.
  4. Genus

Explanation

In binomial nomenclature the first word is the genus and the second is the specific epithet. Hence Mangifera is the genus and indica is the species epithet, together forming the species name. The author's name, when cited, is written after the binomial and is not part of the two-word name.

Question 4Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following groups of algae is characterised by the presence of chlorophyll a and b, storage of starch inside chloroplasts, and cell walls containing cellulose?

  1. Chlorophyceae Correct answer.
  2. Rhodophyceae
  3. Cyanophyceae
  4. Phaeophyceae

Explanation

Green algae (Chlorophyceae) contain chlorophyll a and b, store starch within the chloroplast, and possess cellulose cell walls, features they share with land plants. Brown algae use fucoxanthin and store laminarin, red algae contain phycoerythrin and store floridean starch, and cyanobacteria are prokaryotic.

Question 5Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

In the classification of bryophytes, the liverworts are placed in which class?

  1. Anthocerotae
  2. Hepaticae Correct answer.
  3. Musci
  4. Pteropsida

Explanation

Bryophyta is traditionally divided into three classes: Hepaticae (liverworts), Anthocerotae (hornworts) and Musci (mosses). Liverworts are therefore placed in Hepaticae, distinguished by their thalloid or leafy gametophytes and simple sporophytes.

Question 6Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following animals is a coelenterate exhibiting radial symmetry and a gastrovascular cavity with a single opening?

  1. Earthworm
  2. Ascaris
  3. Hydra Correct answer.
  4. Planaria

Explanation

Hydra is a cnidarian (coelenterate) with radial symmetry, two germ layers, and a single-opening gastrovascular cavity. Its diploblastic body plan and tentacles bearing nematocysts are diagnostic. The other options are bilaterally symmetrical worms.

Question 7Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following is a defining feature of the phylum Echinodermata?

  1. Presence of a water vascular system with tube feet Correct answer.
  2. Presence of nephridia for excretion in each segment
  3. Presence of a notochord in the adult stage
  4. Presence of jointed appendages and an exoskeleton of chitin

Explanation

Echinoderms possess a unique water vascular system, a network of canals derived from the coelom that operates tube feet for locomotion, feeding and respiration. This system, together with calcareous ossicles and pentaradial symmetry in adults, identifies the phylum.

Question 8Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

The scientific name of a species must be printed in italics and, when handwritten, underlined. Which statement best explains the reason for this convention?

  1. It distinguishes the scientific name from the surrounding ordinary text Correct answer.
  2. It indicates that the author citation has been omitted
  3. It shows that the name is derived from Latin or Greek
  4. It marks the name as belonging to a newly described species

Explanation

The International Code of Zoological Nomenclature and the botanical Code require scientific names to be typographically distinguished from ordinary text, by italics in print and underlining in handwriting. This is a convention of presentation, not a statement about etymology, authorship or novelty of the species.

Question 9Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

A specimen shows the following features: eukaryotic, multicellular, cell walls of chitin, heterotrophic nutrition by absorption, and a body made of filamentous hyphae. To which kingdom should it be assigned?

  1. Fungi Correct answer.
  2. Plantae
  3. Monera
  4. Protista

Explanation

Eukaryotic, multicellular, chitin-walled, absorptive heterotrophs with hyphal bodies are diagnostic of Kingdom Fungi. Plants have cellulose walls and are photosynthetic, protists are largely unicellular, and monerans are prokaryotic.

Question 10Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following statements about the life cycle of brown algae such as Fucus is correct?

  1. Alternation of generations involves an independent haploid thallus and a dependent diploid sporophyte
  2. The dominant phase is a haploid gametophyte and the sporophyte is reduced
  3. The plant body is diploid and meiosis occurs during gamete formation Correct answer.
  4. The plant body is haploid and gametes are produced by mitosis

Explanation

In brown algae such as Fucus the conspicuous plant body is the diploid sporophyte, and gametes are formed after meiosis, so the gametes are the only haploid stage. There is no independent haploid thallus in this genus. This contrasts with the haploid gametophyte dominance seen in many green algae.

Question 11Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which feature of the sporophyte of mosses distinguishes them from the sporophyte of liverworts?

  1. The moss sporophyte is dependent on the gametophyte and bears a capsule with an operculum Correct answer.
  2. The moss sporophyte is haploid and produces gametes
  3. The moss sporophyte lacks a seta and foot
  4. The moss sporophyte is independent and photosynthetic from an early stage

Explanation

The moss sporophyte remains attached to and nutritionally dependent on the gametophyte, but is differentiated into foot, seta and capsule, the capsule typically opening by an operculum. Liverwort sporophytes are simpler, usually with a capsule that dehisces by valves or splits and lacks an operculum.

Question 12Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

In pteridophytes, the prothallus represents which stage of the life cycle?

  1. The diploid gametophyte
  2. The diploid sporophyte
  3. The haploid sporophyte
  4. The haploid gametophyte Correct answer.

Explanation

The prothallus is the free-living, photosynthetic, haploid gametophyte of ferns, bearing antheridia and archegonia. It arises from a germinating spore and produces gametes by mitosis. The familiar leafy fern plant is the diploid sporophyte.

Question 13Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which combination of characters correctly describes the phylum Arthropoda?

  1. Bilaterally symmetrical, segmented, with jointed appendages and an exoskeleton of chitin Correct answer.
  2. Bilaterally symmetrical, segmented, with a closed circulatory system and nephridia
  3. Bilaterally symmetrical, unsegmented, with a notochord and pharyngeal gill slits
  4. Radially symmetrical, unsegmented, with a calcareous endoskeleton

Explanation

Arthropods are bilaterally symmetrical, metamerically segmented animals with jointed appendages and a chitinous exoskeleton that is shed by moulting. They have an open circulatory system and excretory organs such as Malpighian tubules or green glands, not nephridia.

Question 14Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following is the correct sequence of taxonomic categories from the most inclusive to the least inclusive?

  1. Kingdom, phylum, class, order, family, genus, species Correct answer.
  2. Kingdom, phylum, order, class, family, genus, species
  3. Phylum, kingdom, class, family, order, genus, species
  4. Kingdom, class, phylum, order, family, genus, species

Explanation

The standard hierarchy descends from kingdom through phylum, class, order, family, genus to species, each level nested within the one above. Any rearrangement of class and phylum or of order and family breaks the nesting order and is therefore wrong.

Question 15Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

A biologist finds an organism with the following features: triploblastic, bilaterally symmetrical, pseudocoelomate, unsegmented, and with a complete digestive tract. Which phylum fits best?

  1. Platyhelminthes
  2. Annelida
  3. Mollusca
  4. Nematoda Correct answer.

Explanation

Nematodes are triploblastic, bilaterally symmetrical, pseudocoelomate and unsegmented worms with a complete digestive tube opening by mouth and anus. Platyhelminths are acoelomate, annelids are true coelomates and segmented, and molluscs are coelomate and typically unsegmented with a mantle.

Question 16Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following features distinguishes the phylum Mollusca from the phylum Annelida?

  1. Presence of radial symmetry in molluscs versus bilateral symmetry in annelids
  2. Presence of jointed appendages in molluscs versus a chitinous exoskeleton in annelids
  3. Presence of a muscular foot and mantle in molluscs versus metameric segmentation with setae in annelids Correct answer.
  4. Presence of a pseudocoelom in molluscs versus a true coelom in annelids

Explanation

Molluscs are characterised by a soft unsegmented body with a muscular foot, a visceral mass and a mantle that often secretes a shell. Annelids are metamerically segmented worms with setae and a true coelom, so the presence of a foot and mantle versus segmentation and setae separates the two phyla.

Question 17Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following animals is a hemichordate that shows a combination of chordate and invertebrate features?

  1. Balanoglossus Correct answer.
  2. Nereis
  3. Branchiostoma
  4. Ascidia

Explanation

Balanoglossus is a hemichordate, possessing a stomochord in the proboscis rather than a true notochord, together with pharyngeal gill slits. It illustrates the intermediate position of hemichordates near the chordate line. Branchiostoma and Ascidia are true chordates, and Nereis is an annelid.

Question 18Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

In the classification of vertebrates, which of the following is a characteristic that separates Chondrichthyes from Osteichthyes?

  1. A cartilaginous skeleton with placoid scales and no swim bladder Correct answer.
  2. A bony skeleton with cycloid scales and a swim bladder
  3. The presence of internal fertilisation
  4. The presence of a two-chambered heart

Explanation

Chondrichthyes have a skeleton made of cartilage, placoid scales, and lack a swim bladder, relying on a large oily liver for buoyancy. Osteichthyes have a bony skeleton with cycloid or ctenoid scales and usually a swim bladder. Both groups have a two-chambered heart, so that feature cannot separate them.

Question 19Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following groups of plants is heterosporous and produces seeds enclosed within an ovary?

  1. Angiosperms Correct answer.
  2. Bryophytes
  3. Pteridophytes
  4. Gymnosperms

Explanation

Angiosperms are heterosporous plants whose ovules are enclosed in an ovary that develops into a fruit, and whose seeds are therefore enclosed. Gymnosperms are also heterosporous but bear naked ovules on cones, while pteridophytes and bryophytes are not seed plants.

Question 20Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

A plant specimen shows the following features: vascular tissue, independent sporophyte, seeds borne on the surface of megasporophylls, and motile sperm in the pollen tube of some genera. Which group does it most likely belong to?

  1. Filicopsida
  2. Cycadopsida Correct answer.
  3. Hepaticae
  4. Dicotyledonae

Explanation

Cycads are gymnosperms with naked seeds on megasporophylls and, uniquely among seed plants, multiflagellate motile sperm released in the pollen chamber. They are vascular with an independent sporophyte. Dicotyledons enclose seeds in an ovary, ferns are seedless, and liverworts lack vascular tissue.

Question 21Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which statement best explains why cyanobacteria were formerly grouped with algae but are now placed in Monera?

  1. They perform oxygenic photosynthesis but lack a membrane-bound nucleus and organelles Correct answer.
  2. They reproduce sexually by conjugation with gamete fusion
  3. They possess chlorophyll b and store starch in chloroplasts
  4. They have cellulose cell walls and flagellated gametes

Explanation

Cyanobacteria carry out oxygenic photosynthesis using chlorophyll a and phycobilins, which is why they were once treated as blue-green algae. However, they are prokaryotic, lacking a nuclear envelope and membrane-bound organelles, so modern classification places them in Monera.

Question 22Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which pairing of excretory structure with animal group is correct?

  1. Malpighian tubules in Annelida and nephridia in Insecta
  2. Flame cells in Nematoda and green glands in Crustacea
  3. Nephridia in Platyhelminthes and flame cells in Mollusca
  4. Flame cells in Platyhelminthes and nephridia in Annelida Correct answer.

Explanation

Flame cells (protonephridia) are the excretory organs of flatworms, while annelids excrete by metamerically arranged nephridia. Malpighian tubules occur in insects and other arthropods, green glands in crustaceans, and nematodes use renette gland cells.

Question 23Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

Which of the following best justifies placing birds and mammals in separate classes rather than in a single class of warm-blooded vertebrates?

  1. Birds are oviparous while all mammals are viviparous, so reproduction alone separates the classes
  2. Birds lack a diaphragm while mammals possess one, and this single feature defines the classes
  3. Birds have feathers and a four-chambered heart with a single aortic arch, while mammals have hair and a four-chambered heart with a single aortic arch on the left Correct answer.
  4. Birds have a cloaca while mammals never possess one, so excretion separates the classes

Explanation

Birds and mammals share endothermy and a four-chambered heart, so those features cannot be used to unite them. They differ in integumentary structures (feathers versus hair and mammary glands) and in aortic arch patterns, and these combined characters justify separate classes.

Question 24Diversity of Living Organisms (taxonomy, classification, plant and animal diversity)

A newly discovered organism is multicellular, heterotrophic, lacks cell walls, and its cells are organised into tissues with a body cavity lined by mesoderm. Which of the following conclusions is most defensible?

  1. It is a fungus because it is heterotrophic and multicellular
  2. It is an animal belonging to Animalia and is likely a coelomate Correct answer.
  3. It is a plant because it is multicellular and organised into tissues
  4. It is a protist because it lacks cell walls

Explanation

Multicellular heterotrophy without cell walls, together with tissue-level organisation and a mesoderm-lined body cavity, points to Animalia and specifically to a coelomate animal. Fungi have chitinous walls and no mesodermal cavity, plants are photosynthetic, and protists are largely unicellular.

Question 25Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In a dicot stem, the vascular bundles are arranged in a ring and each bundle is described as conjoint, collateral and open. What does the term 'open' specifically indicate about such a bundle?

  1. Cambium is present between xylem and phloem, permitting secondary growth Correct answer.
  2. Xylem completely surrounds the phloem tissue within the bundle
  3. The bundle lacks a bundle sheath of sclerenchyma cells
  4. Phloem lies on both the inner and outer sides of xylem

Explanation

An open vascular bundle contains a strip of intrafascicular cambium between the xylem and phloem, so new secondary vascular tissues can be added during secondary growth. Closed bundles, typical of monocot stems, lack this cambium and cannot grow in thickness this way. The presence of cambium is therefore the defining feature of an open bundle.

Question 26Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

A transverse section of a root shows a central solid core of xylem with protoxylem at the periphery and metaxylem towards the centre, and phloem strands lie between the xylem arms. Which type of vascular arrangement is this?

  1. Concentric amphivasal
  2. Conjoint bicollateral
  3. Conjoint collateral
  4. Radial Correct answer.

Explanation

In a radial vascular arrangement, xylem and phloem occupy separate radii and alternate with each other around a common axis, which is the typical condition in roots. The xylem is exarch, with protoxylem peripheral and metaxylem central. Conjoint arrangements have xylem and phloem on the same radius and are typical of stems.

Question 27Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Which tissue is chiefly responsible for the storage of starch in a mature dicot root such as a carrot, and also constitutes the bulk of the cortex?

  1. Sclerenchyma
  2. Collenchyma
  3. Phloem fibres
  4. Parenchyma Correct answer.

Explanation

Parenchyma cells are thin-walled, living and retain the ability to store reserves, so the bulky cortical region of storage roots is mainly parenchymatous. Their large vacuoles hold starch and other reserves. Collenchyma and sclerenchyma are strengthening tissues with thickened walls poorly suited to bulk storage.

Question 28Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

The stomatal apparatus of a grass leaf differs from that of a typical dicot leaf in that the guard cells are:

  1. Kidney-shaped and flanked by several subsidiary cells
  2. Sunken in pits beneath a thick cuticle
  3. Absent, with gas exchange occurring through lenticels
  4. Dumbbell-shaped with bulbous ends and accompanied by two parallel subsidiary cells Correct answer.

Explanation

In grasses the guard cells are narrow in the middle with swollen bulbous ends, giving a dumbbell shape, and each stoma is flanked by two subsidiary cells lying parallel to the guard cells. Dicot guard cells are typically kidney-shaped. This dumbbell architecture allows efficient opening and closing with relatively little water movement.

Question 29Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In a monocot root, a well-developed endodermis with Casparian thickenings separates the cortex from the stele. What is the principal functional significance of the Casparian strip?

  1. It stores starch that is later mobilised during flowering
  2. It forces water and dissolved ions to pass through the symplast by blocking the apoplastic route Correct answer.
  3. It accelerates the apoplastic movement of water into the xylem vessels
  4. It permits free diffusion of solutes between cortex and stele through the cell walls

Explanation

The Casparian strip is a band of suberin and lignin in the radial and transverse walls of endodermal cells that blocks the apoplastic pathway. Water and ions must therefore cross the endodermal plasma membrane, giving the root selective control over what enters the stele. This is why the endodermis is described as a physiological checkpoint.

Question 30Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Which meristematic region of a root is responsible for producing the root cap cells that are continuously sloughed off as the root pushes through soil?

  1. Pericycle
  2. Phellogen
  3. Quiescent centre
  4. Calyptrogen Correct answer.

Explanation

The calyptrogen is the specialised meristematic layer at the root tip that divides to replenish the root cap as outer cells are worn away. The quiescent centre lies just behind it and divides only rarely, acting as a reserve. The pericycle and phellogen produce lateral roots and cork respectively.

Question 31Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

A student examines a section and notes a single layer of barrel-shaped cells with unevenly thickened corners, no intercellular spaces, and living protoplasts. Which tissue has been described?

  1. Sclerenchyma
  2. Epidermis
  3. Collenchyma Correct answer.
  4. Parenchyma

Explanation

Collenchyma is characterised by living cells with unevenly thickened primary walls, typically at the corners, and little or no intercellular space. It provides flexible support to growing organs such as petioles. Parenchyma has thin uniform walls, sclerenchyma has lignified secondary walls and is usually dead, and epidermis is a surface layer with cuticle.

Question 32Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In the anatomy of a dorsiventral dicot leaf, the palisade mesophyll is typically located:

  1. Between the two bundle sheaths of the veins
  2. On the abaxial side, next to the lower epidermis
  3. On the adaxial side, next to the upper epidermis Correct answer.
  4. Uniformly around the midrib vascular bundle

Explanation

In a dorsiventral leaf the palisade tissue lies towards the upper, adaxial surface where light is strongest, and the spongy tissue lies towards the lower surface. The palisade cells are columnar with many chloroplasts, maximising photosynthesis near the illuminated surface. Isobilateral leaves, by contrast, have palisade on both sides.

Question 33Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In a monocot stem such as maize, the vascular bundles are scattered and each is surrounded by a sclerenchymatous bundle sheath. Which additional feature distinguishes these bundles from those of a dicot stem?

  1. They are concentric with phloem surrounding xylem
  2. They are radial with alternating xylem and phloem
  3. They are conjoint and closed, lacking intrafascicular cambium Correct answer.
  4. They are bicollateral with phloem on both sides of xylem

Explanation

Monocot stem bundles are conjoint, collateral and closed, meaning there is no cambium between xylem and phloem, so secondary growth cannot occur. The scattered distribution and prominent bundle sheath are further typical features. Radial and bicollateral conditions belong to roots and certain dicot stems respectively.

Question 34Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Which of the following is a defining characteristic of epithelial tissue in animals?

  1. Cells are closely packed with little intercellular material and rest on a basement membrane Correct answer.
  2. Cells are separated by abundant intercellular matrix carrying blood vessels
  3. Cells are elongated and contain contractile myofibrils
  4. Cells are embedded in a firm cartilage matrix with lacunae

Explanation

Epithelia are composed of closely apposed cells with minimal intercellular space, and they sit on a basement membrane that separates them from underlying connective tissue. They are avascular and are nourished by diffusion from the connective tissue below. Abundant matrix or contractile fibrils characterise other tissue types.

Question 35Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

The epithelium lining the alveoli of the lungs and the endothelium of blood capillaries is best described as:

  1. Ciliated columnar epithelium
  2. Simple squamous epithelium Correct answer.
  3. Simple cuboidal epithelium
  4. Stratified squamous epithelium

Explanation

Simple squamous epithelium consists of a single layer of flattened cells, giving the thinnest possible barrier for diffusion of gases and exchange of materials. Alveoli and capillary walls both require minimal diffusion distance. Cuboidal and columnar epithelia are thicker and suited to secretion, absorption or protection.

Question 36Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In a neuron, which part contains the nucleus and the bulk of the organelles and is the site of most protein synthesis?

  1. Cyton (cell body) Correct answer.
  2. Node of Ranvier
  3. Axon
  4. Dendrite

Explanation

The cyton or cell body contains the nucleus, Nissl granules and most organelles, so it carries out the metabolic and synthetic work of the neuron. Dendrites conduct impulses towards the cyton and the axon conducts away from it. Nodes of Ranvier are gaps in the myelin sheath along the axon.

Question 37Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Smooth muscle fibres differ from skeletal muscle fibres in that smooth muscle fibres are:

  1. Striated, uninucleate and joined by intercalated discs
  2. Non-striated, spindle-shaped and under involuntary control Correct answer.
  3. Non-striated, multinucleate and attached to bones by tendons
  4. Striated, multinucleate and under voluntary control

Explanation

Smooth muscle cells are spindle-shaped, uninucleate and lack striations because their contractile filaments are not arranged in regular sarcomeres. They are involuntary and occur in the walls of the gut, blood vessels and other viscera. Striated voluntary muscle is skeletal, while striated involuntary muscle with intercalated discs is cardiac.

Question 38Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Which connective tissue cell type is chiefly responsible for secreting the collagen fibres and ground substance of loose connective tissue?

  1. Mast cell
  2. Adipocyte
  3. Fibroblast Correct answer.
  4. Macrophage

Explanation

Fibroblasts are the principal resident cells of connective tissue proper and synthesise collagen, elastin and the amorphous ground substance. Mast cells release histamine and heparin, macrophages phagocytose debris, and adipocytes store fat. Each of these has a distinct function rather than matrix production.

Question 39Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In a transverse section of a woody dicot stem, which sequence correctly describes the tissues encountered from the outer surface inward?

  1. Epidermis, vascular cambium, cortex, secondary phloem, secondary xylem, pith
  2. Cortex, cork, secondary xylem, vascular cambium, secondary phloem, pith
  3. Cork, cork cambium, cortex, secondary phloem, vascular cambium, secondary xylem, pith Correct answer.
  4. Cork, cortex, vascular cambium, secondary xylem, secondary phloem, pith

Explanation

In a woody stem the outer bark consists of cork produced by the cork cambium, followed inward by cortex remnants, secondary phloem, the vascular cambium, secondary xylem and finally the pith at the centre. The vascular cambium always lies between phloem outside and xylem inside. Any sequence that reverses phloem and xylem or misplaces the cambium is incorrect.

Question 40Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In a typical dicot leaf, the midrib vascular bundle is described as conjoint and collateral with xylem towards the upper side. Which observation explains why xylem lies adaxially?

  1. The bundle is conjoint collateral, so xylem and phloem lie on the same radius with xylem adaxial Correct answer.
  2. The bundle is concentric amphicribral, so phloem encloses xylem
  3. The bundle is bicollateral, so phloem occurs on both sides of xylem
  4. The bundle is radial, so xylem and phloem alternate on separate radii

Explanation

Leaf veins are conjoint collateral bundles in which xylem and phloem share the same radius, with xylem usually facing the upper surface and phloem the lower. This orientation is consistent with the adaxial position of xylem in the midrib. Radial, bicollateral and amphicribral arrangements do not describe the typical midrib bundle.

Question 41Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Which type of cartilage occurs in the intervertebral discs and the pubic symphysis, where it resists compression and provides flexibility?

  1. Calcified cartilage
  2. Elastic cartilage
  3. Hyaline cartilage
  4. Fibrous cartilage Correct answer.

Explanation

Fibrous cartilage has abundant dense collagen bundles in its matrix, making it the strongest and most compression-resistant type, suited to intervertebral discs and the pubic symphysis. Hyaline cartilage forms smooth articular surfaces and elastic cartilage occurs in the pinna and epiglottis. Calcified cartilage is a degenerative change rather than a normal skeletal type.

Question 42Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

A botanist finds a stem in which each vascular bundle has phloem on both the outer and inner sides of the xylem, with cambium present on both sides of the xylem. Which plant is most likely to show this arrangement?

  1. Maize
  2. Sunflower
  3. Nerium leaf midrib
  4. Cucurbita Correct answer.

Explanation

Bicollateral bundles, with phloem on both sides of the xylem and two strips of cambium, are characteristic of the Cucurbitaceae, of which Cucurbita is a familiar example. Maize has closed collateral bundles and sunflower has ordinary open collateral bundles. The condition is a stem feature, not the typical midrib arrangement of a leaf.

Question 43Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

In the phloem of an angiosperm, which cell type is dead at maturity, lacks a protoplast and provides mechanical support to the sieve elements?

  1. Phloem fibre Correct answer.
  2. Companion cell
  3. Phloem parenchyma
  4. Sieve tube element

Explanation

Phloem fibres are sclerenchymatous cells that are dead at maturity with thick lignified walls, giving mechanical strength to the phloem. Sieve tube elements and companion cells remain living, and phloem parenchyma is also living. Only the fibre is a dead supporting element.

Question 44Structural Organisation in Plants and Animals (morphology, anatomy, animal tissues)

Which statement best explains why monocot stems usually cannot increase in girth through secondary growth, whereas dicot stems can?

  1. Monocot stems lack a pericycle, so no lateral roots can form
  2. Monocot stems have no epidermis and therefore cannot form cork
  3. Monocot stems possess only primary phloem and no xylem at all
  4. Monocot vascular bundles are closed, having no intrafascicular cambium, and lack a continuous cambial ring Correct answer.

Explanation

Secondary growth requires a continuous cylinder of vascular cambium. In monocot stems the bundles are closed and scattered, so no intrafascicular cambium forms and no continuous cambial ring can be established. Dicot stems have open bundles in a ring, allowing the cambium to become continuous and produce secondary xylem and phloem.

Question 45Cell Structure and Function (cell biology, biomolecules, cell cycle)

Which organelle is the primary site of ATP synthesis by oxidative phosphorylation in a eukaryotic cell?

  1. Smooth endoplasmic reticulum
  2. Mitochondrion Correct answer.
  3. Golgi apparatus
  4. Lysosome

Explanation

The inner mitochondrial membrane carries the electron transport chain and ATP synthase, so oxidative phosphorylation occurs there. The other listed organelles handle modification, digestion, or lipid synthesis rather than bulk ATP production.

Question 46Cell Structure and Function (cell biology, biomolecules, cell cycle)

A cell is placed in a hypotonic solution. What is the expected immediate osmotic response in an animal cell?

  1. No net water movement occurs across the membrane
  2. Water leaves the cell and it shrinks
  3. Solute moves out until concentrations equalise
  4. Water enters the cell and it may swell and lyse Correct answer.

Explanation

A hypotonic solution has a lower solute concentration than the cytoplasm, so water moves in by osmosis down its water-potential gradient. An animal cell without a wall cannot resist the resulting turgor pressure and may burst.

Question 47Cell Structure and Function (cell biology, biomolecules, cell cycle)

Which polysaccharide is the principal structural component of plant cell walls?

  1. Chitin
  2. Starch
  3. Glycogen
  4. Cellulose Correct answer.

Explanation

Cellulose is a beta-1,4-linked glucose polymer whose straight chains form microfibrils that give plant walls tensile strength. Starch and glycogen are storage polysaccharides, and chitin builds fungal walls and arthropod exoskeletons.

Question 48Cell Structure and Function (cell biology, biomolecules, cell cycle)

During which phase of mitosis do sister chromatids separate and move toward opposite poles?

  1. Prophase
  2. Telophase
  3. Anaphase Correct answer.
  4. Metaphase

Explanation

At anaphase the cohesin links holding sister chromatids are cleaved and spindle fibres shorten, drawing each chromatid to a pole. Prophase prepares chromosomes, metaphase aligns them, and telophase rebuilds nuclei.

Question 49Cell Structure and Function (cell biology, biomolecules, cell cycle)

Which molecule serves as the immediate energy currency that couples exergonic and endergonic reactions in cells?

  1. Glucose
  2. ATP Correct answer.
  3. NADPH
  4. Pyruvate

Explanation

Hydrolysis of ATP to ADP and inorganic phosphate releases free energy that drives endergonic reactions. NADPH and glucose carry reducing power or stored energy but are not the direct donor for most cellular work.

Question 50Cell Structure and Function (cell biology, biomolecules, cell cycle)

Which type of bond links the two strands of a DNA double helix together?

  1. Hydrogen bonds between complementary bases Correct answer.
  2. Peptide bonds between bases
  3. Ionic bonds between phosphate groups
  4. Phosphodiester bonds between sugars

Explanation

Complementary bases on opposite strands pair through hydrogen bonds: two between A and T, three between G and C. Phosphodiester bonds instead join nucleotides along a single strand.