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Karnataka II PUC Biology (KSEAB) study materials
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Karnataka II PUC Biology (KSEAB) practice questions

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Question 1Reproduction

In angiosperms, the embryo sac is produced from the functional megaspore by which sequence of nuclear divisions?

  1. A single amitotic division of the nucellus cell
  2. Two successive mitotic divisions without cytokinesis
  3. One meiotic division followed by fusion of two nuclei
  4. Three successive free-nuclear mitotic divisions followed by cellularisation Correct answer.

Explanation

The functional megaspore undergoes three free-nuclear mitotic divisions, giving eight nuclei, after which cell walls form to produce the seven-celled, eight-nucleate embryo sac. This is the monosporic Polygonum type of development described in the NCERT chapter on sexual reproduction in flowering plants.

Question 2Reproduction

Double fertilisation in angiosperms is so named because

  1. One male gamete fuses with the egg and the other with two polar nuclei Correct answer.
  2. Two eggs are fertilised by a single male gamete
  3. Syngamy and meiosis occur in the same embryo sac
  4. Two pollen tubes enter the ovule simultaneously

Explanation

Double fertilisation refers to two fusion events in the same embryo sac: syngamy, forming the diploid zygote, and triple fusion, in which the second male gamete fuses with the two polar nuclei to form the triploid primary endosperm nucleus. Both events were described by Nawaschin and are characteristic of angiosperms.

Question 3Reproduction

The outer layer of the pollen wall, which is made largely of sporopollenin and often bears species-specific sculpturing, is the

  1. Exine Correct answer.
  2. Intine
  3. Tapetum
  4. Germ pore

Explanation

The exine is the tough outer layer of the pollen grain, composed mainly of sporopollenin, and its patterns are used in palynology to identify species. The inner pectocellulosic layer is the intine, while the tapetum is the nutritive anther wall layer that contributes materials to the exine.

Question 4Reproduction

In a typical dicot embryo, the radicle is derived from which region of the proembryo?

  1. The chalazal end of the suspensor filament
  2. The peripheral cells of the cotyledons
  3. The hypophysis and adjacent cells at the micropylar end Correct answer.
  4. The suspensor cells

Explanation

The embryo proper develops from the apical cell, while the hypophysis and adjacent cells give rise to the radicle and root cap at the micropylar pole. The cotyledons and plumule arise from the apical region, and the suspensor pushes the embryo into the endosperm.

Question 5Reproduction

A plant breeder wants seedless fruit without fertilisation. Which treatment is most appropriate?

  1. Removing the endosperm after fertilisation
  2. Applying auxin to the stigma to block pollen germination
  3. Treating ovules with colchicine to double chromosome number
  4. Spraying the flower buds with gibberellic acid Correct answer.

Explanation

Seedless fruits can be induced by spraying developing ovaries with growth regulators such as gibberellins, which stimulate ovary growth into fruit without fertilisation, a phenomenon called parthenocarpy. This is used commercially in grapes and some citrus.

Question 6Reproduction

Which statement correctly describes the ploidy of structures formed after double fertilisation in a diploid angiosperm?

  1. Zygote is diploid, primary endosperm nucleus is triploid Correct answer.
  2. Zygote is triploid, primary endosperm nucleus is diploid
  3. Both zygote and primary endosperm nucleus are diploid
  4. Zygote is haploid, primary endosperm nucleus is diploid

Explanation

Syngamy fuses one haploid male gamete with the haploid egg to give a diploid zygote, while triple fusion joins one haploid male gamete with two haploid polar nuclei to give a triploid primary endosperm nucleus. The endosperm is therefore generally triploid in angiosperms.

Question 7Reproduction

In a flowering plant, the number of meiotic divisions needed to produce 40 pollen grains and 40 embryo sacs is

  1. 80 and 10
  2. 10 and 40 Correct answer.
  3. 40 and 40
  4. 20 and 40

Explanation

Each microspore mother cell yields four pollen grains after one meiosis, so 40 pollen grains need 10 meioses. Each megaspore mother cell yields only one functional embryo sac, so 40 embryo sacs need 40 meioses.

Question 8Reproduction

The transfer of pollen from the anther of one flower to the stigma of another flower on a different plant of the same species is called

  1. Autogamy
  2. Xenogamy Correct answer.
  3. Cleistogamy
  4. Geitonogamy

Explanation

Xenogamy is cross-pollination between two different plants of the same species, so it involves genetically different pollen and brings about true cross-breeding. Geitonogamy is transfer between flowers of the same plant, and autogamy is self-pollination within one flower.

Question 9Reproduction

Which floral adaptation is most characteristic of pollination by bats?

  1. Bright red tubular flowers with copious dilute nectar and no scent
  2. Tiny green flowers with exposed anthers producing lightweight pollen
  3. Large, dull-coloured nocturnal flowers with strong musty odour and abundant nectar Correct answer.
  4. Small, dry, odourless flowers opening at midday

Explanation

Chiropterophilous flowers are typically large and sturdy, dull in colour, open at night, and produce a strong musty odour plus large amounts of nectar and pollen to attract bats. The dull colour is not a disadvantage because bats locate flowers mainly by scent.

Question 10Reproduction

In the grass family, the fruit is typically

  1. A legume that splits along two sutures
  2. A caryopsis in which the pericarp is fused with the seed coat Correct answer.
  3. An aggregate of achenes on a fleshy receptacle
  4. A drupe with a stony endocarp

Explanation

Grasses such as wheat and rice form a caryopsis, a simple indehiscent fruit in which the thin pericarp is firmly united with the seed coat. This fusion is why the grain is described as a single seed-like fruit.

Question 11Reproduction

A fruit that develops from an ovary along with other floral parts such as the thalamus is best described as

  1. A parthenocarpic fruit
  2. A multiple fruit
  3. A true fruit
  4. A false fruit Correct answer.

Explanation

A false or accessory fruit includes non-ovarian tissue, usually the thalamus or receptacle, in addition to the ovary wall; apple and strawberry are familiar examples. A true fruit develops from the ovary alone, as in mango.

Question 12Reproduction

Which layer of the anther wall is directly responsible for nourishing the developing microspores?

  1. Middle layers
  2. Tapetum Correct answer.
  3. Endothecium
  4. Epidermis

Explanation

The tapetum is the innermost anther wall layer, and its cells supply nutrients and sporopollenin precursors to the developing microspores. The epidermis and endothecium provide protection and help in dehiscence, while the middle layers are thin and transient.

Question 13Reproduction

A pollen grain at the time of shedding in most angiosperms contains

  1. Four haploid microspores
  2. Two male gametes and one vegetative cell
  3. A single haploid nucleus only
  4. One generative cell and one vegetative cell Correct answer.

Explanation

Most angiosperm pollen is shed at the two-celled stage, containing a large vegetative cell and a smaller generative cell. The generative cell later divides in the pollen tube to form two male gametes.

Question 14Reproduction

In a species where the chromosome number of the endosperm is 60, the diploid chromosome number of the plant is

  1. 20
  2. 30
  3. 40 Correct answer.
  4. 60

Explanation

The endosperm is triploid, so its chromosome number equals three times the haploid number n. Here 3n = 60, giving n = 20 and 2n = 40 for the plant.

Question 15Reproduction

The main significance of emasculation in artificial hybridisation is to

  1. Increase the number of ovules in the ovary
  2. Kill the pollen grains already present on the stigma
  3. Induce the stigma to become receptive earlier
  4. Prevent self-pollination of the flower before the desired pollen is applied Correct answer.

Explanation

Emasculation is the removal of anthers from a bisexual flower bud before dehiscence, so that the flower cannot self-pollinate and only the pollen chosen by the breeder effects fertilisation. The emasculated flower is then bagged to exclude unwanted pollen.

Question 16Reproduction

Apomixis in some grasses such as species of Poa is best described as

  1. Formation of seeds without fertilisation, often from diploid nucellar cells Correct answer.
  2. Development of fruit without any seed formation
  3. Fertilisation of the egg by a male gamete from another species
  4. Fusion of two polar nuclei before pollination

Explanation

Apomixis is asexual seed formation, and in many grasses it occurs by apospory, in which diploid nucellar cells develop into embryo sacs that form embryos without fertilisation. The resulting seedlings are genetically identical to the parent, which is valuable for preserving hybrid vigour.

Question 17Reproduction

Which statement about the fate of the synergids after fertilisation is correct?

  1. They divide to form the suspensor
  2. They fuse with the antipodal cells to form the zygote
  3. They persist and become the first endosperm cells
  4. They degenerate shortly after fertilisation Correct answer.

Explanation

The two synergids lie beside the egg and help guide the pollen tube, but they degenerate soon after fertilisation. The zygote develops into the embryo, and the primary endosperm nucleus develops into endosperm; neither arises from synergids.

Question 18Reproduction

The scutellum of a maize grain is homologous to which structure of a dicot seed?

  1. The single cotyledon Correct answer.
  2. The coleoptile
  3. The endosperm
  4. The radicle

Explanation

The scutellum is the shield-shaped cotyledon of the grass embryo, specialised to absorb nutrients from the endosperm during germination. It is therefore the monocot equivalent of a dicot cotyledon, not a root or a protective sheath.

Question 19Reproduction

In a typical dicot seed such as bean, the micropyle is important because it

  1. Stores food for the embryo
  2. Anchors the seed to the fruit wall
  3. Secretes enzymes that digest the endosperm
  4. Allows entry of water and the pollen tube during germination and fertilisation Correct answer.

Explanation

The micropyle is a small pore in the seed coat through which water enters to initiate germination, and through which the pollen tube had earlier entered the ovule for fertilisation. It is not a storage or secretory structure.

Question 20Reproduction

Which of the following is an example of a multiple fruit?

  1. Pineapple Correct answer.
  2. Coconut
  3. Mango
  4. Pea

Explanation

A multiple fruit develops from the fused ovaries of many flowers in a single inflorescence, as in pineapple and jackfruit. Mango, pea and coconut each develop from the ovary of a single flower and are simple fruits.

Question 21Reproduction

In ovules with anatropous orientation, the micropyle and funicle lie close together because the ovule

  1. Has no integuments around the nucellus
  2. Is bent so that the body of the ovule is turned through about 180 degrees Correct answer.
  3. Develops from the integument alone
  4. Is curved so that the chalaza and micropyle lie in a straight line

Explanation

In an anatropous ovule the body is bent so that the micropyle comes to lie near the funicle and the chalaza is at the opposite end. This is the commonest orientation in angiosperms and is easily recognised by the parallel alignment of funicle and micropyle.

Question 22Reproduction

A farmer notices that a hybrid variety of cotton gives excellent yield in the first year but poor, variable yield when seeds from that crop are sown the next year. The most likely explanation is

  1. The crop became apomictic in the second year
  2. The endosperm was not formed in the first year
  3. Segregation of alleles in the hybrid reduced vigour in the next generation Correct answer.
  4. The hybrid lost its chromosomes during seed storage

Explanation

Hybrid vigour is highest in the F1 generation, and selfing of an F1 produces segregating F2 progeny with reduced and uneven performance. This is why breeders supply fresh hybrid seed each season rather than letting farmers save seed.

Question 23Reproduction

Which statement about vegetative propagation in sugarcane is correct?

  1. It requires meiosis in the nodal buds
  2. It depends on fertilisation of the axillary buds
  3. It produces genetically uniform plants from stem cuttings Correct answer.
  4. It produces offspring with new allele combinations

Explanation

Sugarcane is propagated from stem segments bearing nodes, and each bud grows into a clone genetically identical to the parent. Because no meiosis or fertilisation occurs, the offspring retain the parental genotype, which is useful for maintaining a superior variety.

Question 24Reproduction

In which situation would self-pollination be expected to reduce genetic variation most strongly over successive generations?

  1. A cleistogamous species that never opens its flowers Correct answer.
  2. A dioecious species with wind-dispersed pollen
  3. A species showing protandry with an insect visitor
  4. A self-incompatible species growing in a mixed population

Explanation

Cleistogamous flowers never open, so pollen is transferred to the stigma of the same flower before any chance of cross-pollination, giving obligate selfing. Continued selfing increases homozygosity and reduces genetic variation in the population.

Question 25Reproduction

The hilum of a seed marks the point where the

  1. Seed was attached to the funicle Correct answer.
  2. Endosperm makes contact with the aleurone layer
  3. Cotyledons are joined to the plumule
  4. Radicle emerges during germination

Explanation

The hilum is the scar left on the seed coat at the place where the seed was attached to the funicle, the stalk connecting it to the fruit wall. The micropyle, a separate small pore nearby, is the channel for water entry.

Question 26Reproduction

In a typical angiosperm ovule, the embryo sac is surrounded by a protective tissue called the nucellus, which in turn is enclosed by integuments. Which structure is the small opening at the micropylar end that allows the pollen tube to enter?

  1. Micropyle Correct answer.
  2. Raphe
  3. Funicle
  4. Chalaza

Explanation

The micropyle is the narrow pore at the micropylar pole of the ovule, formed by the integuments leaving a gap, and it is the route through which the pollen tube gains entry to the embryo sac during fertilisation. The chalaza is the basal region opposite the micropyle where the integuments and nucellus merge.

Question 27Reproduction

A student examines a transverse section of a mature anther and identifies four distinct wall layers plus the central sporogenous tissue. Which sequence gives the correct order of anther wall layers from the outermost inward?

  1. Epidermis, tapetum, endothecium, middle layers
  2. Epidermis, endothecium, middle layers, tapetum Correct answer.
  3. Tapetum, middle layers, endothecium, epidermis
  4. Endothecium, epidermis, tapetum, middle layers

Explanation

A typical angiosperm anther wall consists of four layers arranged from outside inward as epidermis, endothecium, middle layers and tapetum, with the tapetum lying closest to the pollen mother cells. The tapetum is the innermost nutritive layer, so any sequence placing it outermost is inverted.

Question 28Reproduction

In a flowering plant, the megaspore mother cell undergoes meiosis to produce four megaspores, yet only one functional embryo sac normally develops. What happens to the other three megaspores in the common Polygonum type of embryo sac development?

  1. They divide mitotically to form the antipodal cells of the embryo sac
  2. They each develop into a separate embryo sac within the same ovule
  3. They degenerate, and the chalazal megaspore develops into the embryo sac Correct answer.
  4. They fuse with the functional megaspore to form a triploid embryo sac

Explanation

In monosporic Polygonum type development, meiosis yields a linear tetrad of megaspores in which the three micropylar megaspores degenerate while the chalazal megaspore remains functional. This single functional megaspore then undergoes three free-nuclear mitotic divisions to produce the eight-nucleate, seven-celled embryo sac.

Question 29Reproduction

During artificial hybridisation of a bisexual crop, a breeder removes the anthers from a flower bud before it opens and then covers the flower with a butter-paper bag. Which pair of purposes do these two steps serve respectively?

  1. Emasculation prevents self-pollination; bagging prevents unwanted cross-pollination Correct answer.
  2. Emasculation induces apomixis; bagging prevents seed dispersal
  3. Emasculation prevents cross-pollination; bagging prevents self-pollination
  4. Emasculation promotes pollen germination; bagging maintains humidity for the pollen tube

Explanation

Emasculation removes the anthers of the bisexual flower so that its own pollen cannot reach the stigma, thereby preventing self-pollination. Bagging then isolates the emasculated flower from pollen carried by wind or insects, so that only the pollen deliberately applied by the breeder effects fertilisation.

Question 30Reproduction

A plant produces seeds that are viable and genetically identical to the parent even though no meiosis or fertilisation occurs, and the embryo arises directly from a diploid nucellar cell. Which term best describes this phenomenon?

  1. Apomixis Correct answer.
  2. Vivipary
  3. Parthenocarpy
  4. Polyembryony

Explanation

Apomixis is the production of seeds without meiosis and fertilisation, so the embryo is genetically identical to the maternal parent; nucellar embryony in citrus is a classic example. Because no gamete fusion occurs, the offspring retain the maternal genotype, which is why apomixis is of great interest for fixing hybrid vigour.

Question 31Reproduction

A botanist studying dispersal finds a fruit that develops from a single flower with many free carpels, each carpel forming its own small unit on a common receptacle, as in Michelia. How should this fruit be classified?

  1. A simple fruit
  2. A multiple fruit
  3. An aggregate fruit Correct answer.
  4. A composite fruit formed from an inflorescence

Explanation

An aggregate fruit develops from a single flower that has many free carpels, each carpel forming a small fruitlet on the same receptacle; Michelia and lotus are typical examples. A multiple fruit, by contrast, develops from an entire inflorescence in which the flowers fuse, as in pineapple.

Question 32Reproduction

A student calculates that a particular angiosperm seed contains an endosperm with 90 chromosomes. Assuming normal double fertilisation and a diploid sporophyte, what is the chromosome number of the zygote and of each polar nucleus respectively?

  1. 60 and 30 Correct answer.
  2. 90 and 45
  3. 30 and 60
  4. 45 and 45

Explanation

Endosperm is triploid, formed by fusion of one haploid male gamete with two haploid polar nuclei, so 3n = 90 gives n = 30. The zygote is diploid (2n = 60), and each polar nucleus is haploid (n = 30), which is consistent with the triploid endosperm.

Question 33Sexual Reproduction in Flowering Plants

In a typical angiosperm ovule, which structure undergoes meiosis to produce the megaspore mother cell's haploid products?

  1. The antipodal cells at the chalazal end
  2. The integument cells surrounding the nucellus
  3. The synergids of the mature embryo sac
  4. The megaspore mother cell present in the nucellus Correct answer.

Explanation

The megaspore mother cell (megasporocyte) is a diploid cell of the nucellus that undergoes meiosis to give four haploid megaspores, of which usually only one survives. The integuments are sporophytic protective layers and do not undergo meiosis to form the embryo sac.

Question 34Sexual Reproduction in Flowering Plants

A typical Polygonum-type embryo sac of a flowering plant contains how many nuclei and how many cells at maturity?

  1. Four nuclei distributed in four cells
  2. Eight nuclei distributed in seven cells Correct answer.
  3. Sixteen nuclei distributed in seven cells
  4. Eight nuclei distributed in eight cells

Explanation

After three free-nuclear mitotic divisions the embryo sac has eight nuclei; cellularisation then produces seven cells: three antipodals, two synergids, one egg cell and one central cell with two polar nuclei. Hence eight nuclei but seven cells.

Question 35Sexual Reproduction in Flowering Plants

Which floral whorl is directly responsible for producing the microspores that develop into pollen grains?

  1. The sporogenous tissue inside the microsporangium of the anther Correct answer.
  2. The secretory cells of the tapetum lining the anther locule
  3. The nucellar cells of the ovule
  4. The cells of the stigma papillae

Explanation

Microspores arise from microspore mother cells in the sporogenous tissue of the anther locules, which are the microsporangia. The tapetum nourishes developing pollen but does not itself give rise to microspores.

Question 36Sexual Reproduction in Flowering Plants

In an angiosperm anther, the innermost wall layer that nourishes the developing pollen grains is the

  1. middle layer
  2. endothecium
  3. tapetum Correct answer.
  4. epidermis

Explanation

The anther wall consists of epidermis, endothecium, middle layers and tapetum, with the tapetum being the innermost nutritive layer. It secretes nutrients and sporopollenin precursors that support microspore development.

Question 37Sexual Reproduction in Flowering Plants

A pollen grain of a flowering plant is shed at the two-celled stage. Which cells does it contain at that moment?

  1. Two male gametes and a tube cell
  2. A generative cell and two male gametes
  3. A vegetative cell and two synergids
  4. A vegetative cell and a generative cell Correct answer.

Explanation

In the majority of angiosperms the microspore divides mitotically to give a large vegetative (tube) cell and a small generative cell before shedding. The generative cell later divides in the pollen tube to form the two male gametes.

Question 38Sexual Reproduction in Flowering Plants

In a flowering plant, the pollen tube usually enters the ovule through the micropyle and discharges its contents into which cell of the embryo sac?

  1. The central cell, before the polar nuclei fuse
  2. An antipodal cell at the chalazal pole
  3. The egg cell directly, without passing through a synergid
  4. One of the synergids, which degenerates at the time of entry Correct answer.

Explanation

During porogamy the pollen tube enters through the micropyle and typically penetrates one synergid, the filiform apparatus guiding it, and discharges the two male gametes there. One gamete fuses with the egg and the other with the secondary nucleus.

Question 39Sexual Reproduction in Flowering Plants

A plant shows pollen grains that are shed at the three-celled stage. What has already happened inside such a pollen grain before dehiscence?

  1. The microspore mother cell has completed meiosis inside the pollen grain
  2. The generative cell has divided to form two male gametes Correct answer.
  3. The vegetative nucleus has divided into two tube nuclei
  4. The pollen grain has fused with a synergid

Explanation

In the three-celled condition the generative cell divides mitotically within the pollen grain before shedding, producing two male gametes alongside the vegetative cell. This occurs in species such as rice and wheat, whereas most plants shed two-celled pollen.

Question 40Sexual Reproduction in Flowering Plants

A botanist examines an ovule in which the micropyle and chalaza lie in a straight line and the funiculus is attached at right angles. Which type of ovule is being described?

  1. Anatropous
  2. Campylotropous
  3. Orthotropous Correct answer.
  4. Amphitropous

Explanation

An orthotropous (atropous) ovule is straight, with micropyle, chalaza and funiculus in one line and the funiculus attached at the base at right angles to the micropylar axis. In anatropous ovules the body is bent through 180 degrees so the micropyle lies close to the funiculus.

Question 41Sexual Reproduction in Flowering Plants

Which statement correctly describes the ploidy of the endosperm and the embryo in a typical angiosperm after double fertilisation?

  1. Endosperm is diploid and the embryo is triploid
  2. Both endosperm and embryo are diploid
  3. Endosperm is triploid and the embryo is diploid Correct answer.
  4. Endosperm is haploid and the embryo is diploid

Explanation

Triple fusion joins one male gamete with the two polar nuclei (or secondary nucleus) to give a triploid primary endosperm nucleus, while syngamy gives a diploid zygote. Thus the endosperm is generally triploid and the embryo diploid.

Question 42Sexual Reproduction in Flowering Plants

In an angiosperm ovule showing monosporic development, three of the four megaspores degenerate. Which megaspore normally survives and gives rise to the embryo sac?

  1. The chalazal megaspore Correct answer.
  2. The micropylar megaspore
  3. All four megaspores fuse before development
  4. The middle megaspore of the linear tetrad

Explanation

In the monosporic Polygonum type, the functional megaspore is usually the chalazal one of the tetrad, while the three micropylar megaspores degenerate. The surviving megaspore undergoes three mitotic divisions to form the eight-nucleate embryo sac.

Question 43Sexual Reproduction in Flowering Plants

Which pollination event is described when pollen from the anther of a flower is transferred to the stigma of another flower borne on a different plant of the same species?

  1. Cleistogamy within a closed bud
  2. Self-pollination, specifically autogamy
  3. Cross-pollination, specifically xenogamy Correct answer.
  4. Geitonogamy between flowers of one plant

Explanation

Transfer between flowers on genetically different plants of the same species is xenogamy, a form of cross-pollination that brings genetically different pollen to the stigma. Geitonogamy, by contrast, involves two flowers of the same plant and is functionally self-pollination.

Question 44Sexual Reproduction in Flowering Plants

Which adaptation most directly favours wind pollination (anemophily) in a flowering plant?

  1. Sticky pollen massed into pollinia
  2. Large, feathery stigmas and light, dry, numerous pollen grains Correct answer.
  3. Strong scent produced mainly at night
  4. Brightly coloured petals with nectar-secreting glands

Explanation

Anemophilous flowers typically lack showy perianth, produce abundant light dry pollen and expose large feathery stigmas that trap airborne grains. Bright petals, nectar, pollinia and scent are features that attract or attach animal pollinators.

Question 45Sexual Reproduction in Flowering Plants

In a flowering plant, the filiform apparatus is a specialised structure associated with which cells of the embryo sac?

  1. The central cell
  2. The synergids Correct answer.
  3. The antipodal cells
  4. The egg cell

Explanation

The filiform apparatus is a thickened, finger-like ingrowth of the cell wall at the micropylar end of the synergids. It is believed to guide the pollen tube towards the synergid and assist in the uptake and transport of substances.

Question 46Sexual Reproduction in Flowering Plants

An angiosperm species produces seeds in which the pericarp is fleshy and the seed coat is thin, and the fruit develops without fertilisation of the ovule. This condition is best described as

  1. parthenocarpy Correct answer.
  2. vivipary
  3. polyembryony
  4. apomixis

Explanation

Parthenocarpy is the development of fruit without fertilisation, giving seedless fruits such as in some banana varieties, often induced by growth substances. Apomixis refers to seed formation without fertilisation, which is a different phenomenon.

Question 47Sexual Reproduction in Flowering Plants

A seed of a flowering plant is described as albuminous. Which statement correctly accounts for this condition?

  1. The cotyledons store all the reserve food and no endosperm remains
  2. The endosperm is completely consumed by the developing embryo
  3. The seed coat is fused with the pericarp
  4. The endosperm persists and is retained in the mature seed Correct answer.

Explanation

Albuminous (endospermic) seeds retain a persistent endosperm that stores reserves, as in castor and wheat. Non-albuminous seeds, such as pea and groundnut, have the endosperm fully consumed by the embryo, with cotyledons storing the food.

Question 48Sexual Reproduction in Flowering Plants

In a monosporic embryo sac, the two polar nuclei that take part in triple fusion are derived from which nuclei of the eight-nucleate stage?

  1. Both from the micropylar group of four nuclei
  2. Both from the chalazal group of four nuclei
  3. One from the micropylar group and one from the chalazal group Correct answer.
  4. One from a synergid and one from an antipodal cell

Explanation

After the eight nuclei arrange in two groups of four, one nucleus from each group migrates to the centre to form the two polar nuclei of the central cell. These two polar nuclei then fuse with one male gamete during triple fusion.

Question 49Human Reproduction and Reproductive Health

Which structure in the human male reproductive system secretes the bulk of the fluid that makes up semen?

  1. Seminal vesicles Correct answer.
  2. Rete testis
  3. Bulbourethral glands
  4. Epididymis

Explanation

The seminal vesicles contribute roughly 60 per cent of seminal plasma, supplying fructose and prostaglandins that nourish and help transport sperm. The prostate and bulbourethral glands add smaller volumes, so the vesicles are correctly described as the major source.

Question 50Human Reproduction and Reproductive Health

The hormone that triggers ovulation by causing a sudden surge in the middle of the menstrual cycle is secreted by which structure?

  1. Developing follicle
  2. Corpus luteum
  3. Hypothalamus
  4. Anterior pituitary Correct answer.

Explanation

A sharp rise in luteinising hormone from the anterior pituitary ruptures the mature Graafian follicle and releases the oocyte. The hypothalamus releases GnRH, which regulates but does not itself secrete the ovulatory surge hormone.